tag:blogger.com,1999:blog-56455933415282112882024-03-13T13:25:30.051-07:00Astro BasicsAstronomy Made Easy | How to See Stars, Planets, Galaxies, Nebulas, and other Sky Objectssaundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.comBlogger36125tag:blogger.com,1999:blog-5645593341528211288.post-56084874973222212762013-11-08T14:42:00.000-08:002013-11-08T14:42:07.301-08:00Eight Great Telescopes That Aren't HubbleThe <a href="http://www.stsci.edu/hst/">Hubble Space Telescope</a> has successfully become the most famous telescope in the world. It has maintained this popularity through many years of operation, repeated news events surrounding the telescope, and promotion through sharing its imagery with the public through various venues on the internet. It's so well known that any time an average member of the public sees a detailed astrophoto they're more likely than not to ask if it's a Hubble image.<br />
<br />
But Hubble isn't the only great telescope out there. In fact, while it is still a very valuable instrument contributing much to current science, its capabilities have in many ways been eclipsed by other instruments. After all, the Hubble was conceived and designed when an Apple II computer, running at 1MHz with an 8 bit processor and about 128KB of RAM was a serious work computer. So, while we recognize and accept the greatness of Hubble, let's have a look at some other telescopes that have been eclipsed by its popularity.<br />
<br />
<b style="color:#77ff77;">The Chandra X-Ray Observatory</b><br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/96/Chandra_X-ray_Observatory.jpg/450px-Chandra_X-ray_Observatory.jpg" alt="Chandra X Ray Observatory Satellite" /></center>The <a href="http://chandra.harvard.edu/">Chandra X-Ray Observatory</a> was one of Hubble's sister scopes in NASA's Great Observatories program. While Hubble was designed to cover the visual and near-infrared part of the electromagnetic spectrum, Chandra covers X-Rays. One of the great advantages of Hubble was that it was outside the atmosphere, eliminating the effects of the air on its images. In Chandra's case, getting outside the atmosphere is critical, x-rays don't penetrate our atmosphere to any degree. A ground-based x-ray telescope would be blind.<br />
<br />
Despite coming from the same overall program as Hubble, the Chandra has gotten far less notoriety. Its images are no less beautiful, and are arguably more scientifically valuable since much of what Hubble does could be reproduced with other instruments. The same can't be said of Chandra.<br />
<br />
<b style="color:#77ff77;">The Spitzer Space Telescope</b><br />
<br />
<center><img src="http://www.spitzer.caltech.edu/uploaded_files/graphics/high_definition_graphics/0007/5512/SIRTF_ir_rh_4_Ti.jpg?1312912127" alt="Spitzer against an infrared sky in space" style="width:450px" /></center><a href="http://www.spitzer.caltech.edu/">Spitzer</a> was also part of the Great Observatories program. It is the full-featured infrared complement to Hubble. Infrared is another part of the electromagnetic spectrum that is interfered with by the atmosphere far more than visual light. High altitude observatories can get above enough of the atmosphere to do IR observation from the ground, but getting into space is far better.<br />
<br />
Infrared observations are especially important compared to visual light because IR wavelengths penetrate gas and dust better than visual wavelengths. On top of that, the effects of red-shift--light being shifted to lower frequencies by the expansion of the universe--means that to observe the visual light emissions of far away objects in space we need to look for infrared light here. It's been red-shifted out of the visual light spectrum entirely. Observations of the early universe rely on IR telescopes. This is why the new large space telescope, the Keck, often hailed as "Hubble's replacement", is being designed to work in IR wavelengths.<br />
<br />
Aside from its scientific value, Spitzer also produces images of great beauty and wonder. Like Chandra, it has lived in Hubble's shadow for over ten years now.<br />
<br />
The Great Observatories were originally rounded out by the <a href="http://heasarc.gsfc.nasa.gov/docs/cgro/index.html">Compton Gamma Ray Observatory</a>. Its stabilization systems broke down after years of operation, and it was brought back down into the atmosphere for destructive re-entry. The remaining Great Observatories are still working today to produce <a href="http://hubblesite.org/newscenter/archive/releases/2013/44">valuable new science</a>.<br />
<br />
<b style="color:#77ff77;">Fermi Gamma Ray Telescope</b><br />
<br />
<center><img src="http://www.nasa.gov/images/content/188900main_GLASTsat07_lg.jpg" style="width:450px;" alt="Fermi satellite image, a box with wings." /></center><a href="http://fermi.gsfc.nasa.gov/">Fermi</a> is the successor and advancement over the Compton Gamma Ray Telescope. Like the Compton, it is an orbital telescope. It observes the highest energies of radiation in the electromagnetic spectrum. It's been in operation for over five years as of the time I write this, and is extending its mission time in space. We hear about Hubble all the time, but this telescope has been working away in space, revolutionizing science for five years. Have you heard of it? (If you read a lot of astronomy magazines and journals like I do, you almost certainly have--if you get information from less specialized sources, you've could easily have missed it or forgotten about it even if you saw a short segment on it somewhere.)<br />
<br />
Fermi was originally called GLAST after its main instrument, the <a href="http://www-glast.stanford.edu/">Gamma ray Large Area Space Telescope</a>. Once again, this telescope is designed to see things that Hubble can't see. Rather than looking as small, specific parts of the sky it scans the entire sky every three hours. It is used to image particles that are travelling just under the speed of light, the most energetic particles in the universe. This allows us to study physics in ways that we can't reproduce in laboratories on Earth. You think the <a href="http://home.web.cern.ch/about/accelerators/large-hadron-collider">Large Hadron Collider</a> is powerful? The physics powerhouses that Fermi studies make LHC look like a pop-gun!<br />
<br />
<b style="color:#77ff77;">Large Binocular Telescope</b><br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/LargeBinoTelescope_NASA.jpg/450px-LargeBinoTelescope_NASA.jpg" alt="large binocular telescope with doors open, showing dual telescopes inside." /></center>Before Hubble, the <a href="http://www.astro.caltech.edu/palomar/hale.html">Palomar Hale Telescope</a> got all the press. It was the "200 inch telescope", the biggest in the world for a long time. Even after the <a href="http://w0.sao.ru/Doc-en/Telescopes/bta/descrip.html">Bolshoi Telescope</a> was built, many Americans (at least) still thought Palomar was the largest. (Though the Bolshoi has always had problems that kept it from having the best performance. However, it is still used and is being <a href="http://www.skyandtelescope.com/news/New-Eye-for-Giant-Russian-Telescope-148547035.html">upgraded</a> again.<br />
<br />
Today, the relatively unknown <a href="http://www.lbto.org/index.htm">Large Binocular Telescope</a> sports a <em>pair</em> of mirrors, each <b>331 inches</b> in diameter! That means each mirror has over 2.7 times the light collecting area of Palomar's Hale telescope. Together, it's about five and a half times the light collecting area. But, as they say in the commercials, that's not all.<br />
<br />
The Large Binocular Telescope uses adaptive optics (AO). This is a means of flexing the optical surfaces of the telescope to get the best possible image. The adaptation happens in real time, allowing the telescope to eliminate much of the problems from observing from the ground, rather than in space. In essence, if we'd had working adaptive optics back when Hubble was being designed, we would have already had ground-based telescopes that can see as well or better than Hubble! If we'd gone ahead with launching a telescope into space (still a good idea), then we would have had to build a telescope even more amazing than Hubble to justify the extra cost and effort (Hubble cost as much or more than a huge ground-based observatory project.)<br />
<br />
But, reality is that we pulled together all the parts to build adaptive optics into ground based observatories after the commitment had already been made to Hubble. So now we have many ground based observatories that can out-perform Hubble, the Large Binocular Telescope among them.<br />
<br />
<b style="color:#77ff77;">The South African Large Telescope</b><br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/52/SA_large_telescope.jpg/420px-SA_large_telescope.jpg" alt="SALT Observatory in daytime" /></center>The <a href="http://www.salt.ac.za/">South African Large Telescope</a> is the largest telescope in the southern hemisphere. Now, space telescopes like Hubble, Fermi, Spitzer, and Chandra don't care about hemispheres, but here on Earth you can only see so much of the sky from any place on Earth. It has roughly four times the light collecting area of Palomar's 200 inch (5.1m) Hale telescope. Its main mirror is a segmented mirror. Whereas the LBT has two mirrors that work side by side as two optical trains, the SALT telescope has 91 individual mirrors that all work together to form one big mirror, creating a single image. The mirrors are all made to work together through careful alignment using laser calibration. Also, rather than tracking the sky like other telescopes, the telescope stays fixed in place, while the instruments attached to the telescope track to capture the light from the object being observed.<br />
<br />
<b style="color:#77ff77;">The Magellan Telescopes</b><br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/7/79/Magellan_telescopes.jpg" alt="The Magellan Telescope buildings at night, lit by ambient light" style="width:450px;" /><h5>Image by <a href="http://krzul.art.pl/">Krzysztof Ulaczyk</a></h5></center>The <a href="http://obs.carnegiescience.edu/Magellan">Magellan Telescopes</a> are a pair of telescopes that each use a single 6.5 meter mirror. They can work together, like the telescopes in the LBT, or they can work independently. Their large reflecting surfaces are made up of a single mirror, rather than a lot of smaller mirrors put together to act as a single mirror, like SALT. The mirrors are not a single large thick slab, like the Palomar Hale Telescope, however. They have hollows inside, they've got a honeycomb-like structure inside that supports the reflecting surface without being solid. Each mirror has well over 1.5 times the light collecting area of the Hale telescope, and, like the LBT, they are equipped with adaptive optics to clean up the image.<br />
<br />
<b style="color:#77ff77;">The Keck Observatory</b><br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/13/Keck_obervatories.jpg/640px-Keck_obervatories.jpg" style="width:450px;" alt="The twin Keck Telescope Domes" /></center>Hubble's launch ended up being delayed, then, once it was launched, it had optical defects that budget cuts had eliminated the tests to catch (the back-up mirror, which still sits here on the ground, was perfect, so it's not like it would have cost a lot to solve the problem if it had been caught.) This meant a further delay while corrective instruments were designed and a half-billion dollar Space Shuttle mission to perform repairs was mounted. During that time, work on ground-based observatories did not stop.<br />
<br />
The Keck Observatory was the great project that brought together so many of the advancements from the time between the start of work on Hubble and Hubble reaching its scientific potential. It used segmented mirrors to produce a collecting area far greater than the Palomar and Bolshoi telescopes. It added adaptive optics, as well as a second advancement to the optical train, active optics.<br />
<br />
Active optics are similar to adaptive optics, in that they make adjustment to the optics of the telescope in real time to make a better image. Active optics, however, primarily correct environmental problems from being on the ground, rather than correcting problems with the image caused by the atmosphere (which is the purpose of adaptive optics.) Active optics correct for the pull of gravity on the mirrors changing as the telescope moves to follow objects across the sky. It corrects for changes in temperature, mechanical stresses on the mirrors, and so on.<br />
<br />
Active optics keeps the mirrors within the telescope's main reflector as perfect a reflector for the telescope as possible. Then adaptive optics kick in later to clean up the effects of the atmosphere. The result is that the Keck can produce more detailed images than Hubble.<br />
<br />
On top of that, Kick added a second telescope that can combine with the first to work like one really huge telescope. This not only increases the light collecting area, but the apparent aperture size of the telescope. That allows for resolution of finer detail (whereas increased collecting area allows the detection of fainter objects.)<br />
<br />
<b style="color:#77ff77;">Gran Telescopo Canarias</b><br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/6/6b/GranTeCan_dome_open_as_the_sun_sets.jpg/640px-GranTeCan_dome_open_as_the_sun_sets.jpg" style="width:450px;" alt="GTC over a cloud deck at sunset" /><h5>Image by <a href="http://commons.wikimedia.org/wiki/User:Njardarlogar">Christoffer H. Støle</a></h5></center>The <a href=http://www.gtc.iac.es/">GTC</a> is an 11.4 meter telescope in the Canary Islands. Like Keck and SALT, it has a segmented mirror. It is one of the most active telescopes in modern science, and it produces <a href="http://www.gtc.iac.es/multimedia/imageGallery.php">stunning images</a>, like Hubble.<br />
<br />
<b style="color:#77ff77;">Atacama Large Millimeter/submillimeter Array</b><br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b4/ALMA_and_a_Starry_Night.jpg/640px-ALMA_and_a_Starry_Night.jpg" alt="The ALMA radio telescopes under a starry sky" style="width:450px;" /><h5>Image by <a href="http://www.eso.org/public/images/potw1238a/">ESO/B. Tafreshi</a> (<a href="http://twanight.org/">twanight.org</a>)</h5></center><a href="http://www.almaobservatory.org/">ALMA</a> will soon be the most powerful telescope. Period. It doesn't even see in light, or infra-red. Instead, it sees electromagnetic radiation in the part of the spectrum in radio waves, just below the IR part of the spectrum. Just as IR can see through gas and dust better than visible light, ALMA can see through it better than IR. Where other scopes can only see cloudy things, ALMA can look inside the clouds to see what's inside. It can see stars that are beginning to form, for example.<br />
<br />
While the far longer wavelengths it observes in would normally mean that it has to give up high detail and positional accuracy to do so, ALMA spreads its reflectors, radio telescopes that all work together as a single instrument, across 16km to get the aperture necessary to get even higher detail than the most detailed visible light and IR telescopes.<br />
<br />
ALMA is the result of many millimeter/submillimeter wave projects coming together into one larger, more capable system. Many countries worked together and committed resources to create ALMA. As I write, ALMA is still in development. It is already producing <a href="http://www.almaobservatory.org/en/visuals/images/astronomy">amazing images</a> that no other telescope in existence can make. If you're looking for a telescope that may steal Hubble's crown as the most talked about telescope, ALMA is a good bet. You can get in before the rush, and start spreading the word.<br />
<br />
<b style="color:#77ff77;">Future Telescopes</b><br />
<br />
There are several more great telescopes on the near horizon, including the <a href="http://www.gmto.org/">Giant Magellan Telescope</a> and NASA's <a href="http://www.jwst.nasa.gov/">James Webb Space Telescope</a>. Not to mention at least two other giant telescopes in the works.<br />
<br />
Hubble will remain useful for as long as it continues to function. Originally, its retirement was planned to come about as a return to Earth via the Space Shuttle. That's not going to happen now, the present plan is to send up a robot spacecraft to guide it to a destructive re-entry. No matter how its life ends, its place in the history books is secure. What's important is to remember that it's not the only game in town.<br />
saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-31032624078488023952013-08-13T16:22:00.000-07:002013-08-13T16:37:13.146-07:00The Sky and What You See in Astronomy<b style="color:#77ff77;">Seeing</b> is the term astronomers use to describe the condition of the atmosphere and the things we look at in space when stargazing. The atmosphere over us is very active, changing from moment to moment. This is why we see the stars twinkle, and why we can see things with our eyes when we learn to <a href="http://astrobasics.blogspot.com/2012/04/stargazing-looking-to-see.html">see actively</a> that we wouldn't see otherwise.<br />
<br />
We live in the lowest part of the atmosphere, even those of us living at high altitude. Within that lower portion there are many layers that swirl and churn invisibly over our heads. That activity becomes visible when we look at light that passes through it, especially light that comes from a "point source", that is, a star.<br />
<br />
Each of these layers has a different temperature. The temperature differences affect how they interact at the boundaries between layers. If you've ever seen a layered fluid, with each layer a different color, as you might get in a layered drink, this is similar to the layers in the atmosphere.<br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/3/3a/Cocktail_B52.jpg" alt="A layered cocktail in a glass."/><h5>Image courtesy of <a href="http://de.wikipedia.org/wiki/Benutzer:Morpheus1703">Morpheus1703</a></h5></center>In the case of a drink in a glass, the layers are static. There's no wind, no forces pushing them one way or another. They lay quietly one on top of the other. In the atmosphere, however, the layers are constantly in motion. Heat radiating from the ground, accumulated from the daytime sunlight, rises from below. Winds blow. And each time that narrow line of light that we see coming from a star passes across the boundary between two layers, its straight line path is disturbed.<br />
<br />
<b style="color:#77ff77;">Refraction</b> is the word for that disturbance. It's the same effect that we use in lenses to focus light. The ordinary type of telescope that people think of, that has a large lens facing the sky and a small lens near your eye is called a refractor telescope because it uses refraction to create its image. Its lenses are made of glass that doesn't change shape much, which refracts light by only so much--no more no less. The atmosphere, however, is like a lot of liquid lenses all flowing over and around each other, constantly changing shape and position.<br />
<br />
<b style="color:#77ff77;">Seeing</b> is the word used in astronomy to describe how good or how bad the atmosphere is affecting the view of the sky outside the atmosphere. When we say the <i>seeing</i> is good, we're saying that the air is relatively still, the images are steady. When we say the <i>seeing</i> is bad, we're saying the turgid atmosphere is making it hard to see a clear image of the astronomical objects we're looking at.<br />
<br />
Seeing can be different at different times of the night, of course. Once the ground has cooled hours after sunset after a sunny day, the seeing can improve dramatically. Or if the weather becomes still. The hours after midnight are the best for seeing in most places. But we can't all choose to engage in our hobby at that time if we have responsibilities in the morning.<br />
<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/e/ef/Seeing_Moon.gif" alt="The effects of seeing on a view of the Moon's surface, which appears to swim before our eyes in this animated image." /><h5>Image courtesy of <a href="http://salzgeber.at/">Philipp Salzgeber</a></h5></center><b style="color:#77ff77;">Fortunately, we have a built in solution.</b> Our eyes have been built to actively adapt to differences in seeing conditions. Normally we use that without thinking about it when viewing normal terrestrial objects under varying conditions of lighting, at different distances, of different colors and materials. We learn to make out objects in shadow when we're standing in sunlight, see differences of texture where there's not much difference in color or lighting is low enough to hide detail. We adjust naturally between something held in our hands to objects in the distance. But many of these conditions don't exist when we're doing astronomy.<br />
<br />
<b style="color:#77ff77;">Everything is infinitely far away</b> so far as our eyes are concerned, when we're doing astronomy. The difference between the Moon, at a mere quarter million miles or about four hundred thousand kilometers, and the Andromeda Galaxy, which is eighty trillion times further away than the Moon, is indistinguishable to our eyes. Everything might as well be equally far away. Our eyes can't distinguish details using the means that we normally use distance to give us cues when we're looking at things on Earth.<br />
<br />
<b style="color:#77ff77;">There is no apparent color</b> for most things in space, with a few exceptions. At that, any color that does exist is pale and washed out by daytime standards. If we see color, it is usually more a matter of contrast between colors of objects that are near each other with significant differences.<br />
<br />
<b style="color:#77ff77;">We need to learn a new set of cues for actively seeing with our eyes</b> for astronomy. It's not difficult, it just takes a little awareness and practice. Knowing what's happening is part of the solution. Aside from color and distance, we have to look hard to see many of the differences in lighting in astro objects, textures are subtle. Instead, <b>we have to learn to use our eyes to "capture" images during moments of good seeing</b> among the bad.<br />
<br />
<b style="color:#77ff77;">Relaxing the eye is key</b> to capturing those moments of clarity. If we're straining to see, we're focusing entirely on the image we see <i>now</i>, trying to pick out detail. Instead, we need to relax and <b>take our time</b>, hanging over the eyepiece for a while, waiting for that moment of clarity to come.<br />
<br />
<b style="color:#77ff77;">The changing of the atmosphere can enhance</b> as well as degrade the image we see, either with our eyes, or through the telescope. If we're waiting for that moment, relaxed, when it comes our eyes will "capture" those moments of superlative clarity. Sure, it's really happening in the brain, where all the image interpretation and processing is happening.<br />
<br />
<b style="color:#77ff77;">This is why the mount of the telescope becomes so important.</b> It needs to be there for our eye, silently doing its job, keeping the telescope on the object we're viewing. We can't be stressing about the fact that the thing we're looking at is sliding out of view. We can't be using our built-in image processors to compensate for a wobbly, weak, or shaking mount--we want to save that capacity for dealing with the thing we can't do anything about, the cylinder of atmosphere that lies between the end of the telescope and the edge of outer space.<br />
<br />
So, remember:<br />
<ol><li>You can get your eyes used to seeing with as much skill as night as during the day, but it'll be unfamiliar at first, and will take a little practice.</li>
<li>You need to relax, and take your time at the eyepiece (even if there's a line of people waiting to look behind you. Take your moment and make it count. I guarantee, you're not going to be there as long as you fear you have been.</li>
<li>The support for the instrument needs to be stable, reliable, and out of your mind when you're at the eyepiece.</li>
<li>The atmosphere is going to do what it's going to do. Even if it is wild, and the image is bouncing around in the scope, there will still be occasional moments when the object you're viewing snaps into clarity. The difference between good seeing and bad is how long you have to wait for that to happen, and how long those moments of clarity last.</li>
</ol><br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Image-February_21%2C_2008_lunar_eclipse_and_stars%2C_West_Hartford%2C_CT%2C_3-17_UTC.jpg/480px-Image-February_21%2C_2008_lunar_eclipse_and_stars%2C_West_Hartford%2C_CT%2C_3-17_UTC.jpg" alt="Image of the Moon during eclipse, with stars in the background of the image." /><h5>Your eyes can't tell that the stars are a few hundred million times as far away, except for Saturn to the lower left of the Moon, which is only 3,500 times as far away as the Moon.<br />
Image courtesy of <a href="http://commons.wikimedia.org/wiki/User:Ragesoss">Ragesoss</a></h5></center><b style="color:#77ff77;">We're lucky to live in a world like this.</b> We don't need to have a view of space to live. Our atmosphere could support us perfectly well as we are, and have constant cloud cover over the entire planet. We could live in a world where the only things we're aware of in space are the Sun and the Moon, and those only as hazy lights in the clouds. Stars, planets, nebulas, and galaxies could all be completely abstract things to us in daily life. They'd be nothing more than scientific oddities, discovered by chance with the invention of radio. Instead, we have an atmosphere that allows us to look directly into the infinite when local conditions permit. We can see the wonders of the universe, the greatest physics laboratory ever, by just looking up. With simple, inexpensive instruments we can get views of these objects that bring their natural detail and beauty into our view.<br />
<br />
A few objects show enough to even the unskilled eye to be magnificent. The Moon, Saturn, Jupiter. Other objects require a little more from us to meet them halfway. The Orion Nebula, Hercules Cluster, Andromeda Galaxy are relatively bright objects with details strong enough to enjoy easily, and there are several dozen more like them. Those object prepare us, and our eyes, for the next level. When we want more.<br />
<br />
The good news is, that as your viewing skills increase, each dimmer, more subtle level of objects that you learn to appreciate has even more objects. From a handful of objects to a couple of dozen, we go to a few hundred. Once we have trained our eyes to appreciate those, objects such as the Black Eye Galaxy, M65 and M66, and the Little Dumbbell, we reach a point where there are not merely hundreds, but thousands of objects waiting for us to see them and appreciate their beauty. A lifetime pursuit opens up.<br />
<br />
<b style="color:#77ff77;">Many amateur astronomers specialize</b> in a particular type of sight they seek, over the course of a season or for a few years. I myself spent a couple of years collecting new galaxies that I had seen. I shifted from that to globular clusters. First, in our own galaxy, then to those visible in other galaxies. Double stars and nebulas of particular types have also been among my "current interests" at different times of my life and under different sky conditions. The eruption of Mount Pinatubo in 1991, and the dust it put into the upper atmosphere, brought my galaxy-seeking to an end at that time, and for a few years afterward. That was when I shifted to globular clusters, which "shine through" the dust better than the faint details of a galaxy's halo.<br />
<br />
That was also one of the times it struck me how lucky we are to have the sky that we have. Frustrating as it can be at times, our atmosphere is a wonderful thing, and our first gateway to the universe.<br />
<center><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Night_Sky_Stars_Trees_02.jpg/480px-Night_Sky_Stars_Trees_02.jpg" alt="The night sky with stars viewed behind the silhouette of a tree bare of leaves." /><h5>Image courtesy of <a href="http://commons.wikimedia.org/wiki/User:Bennett000">Michael J. Bennett</a></h5></center>saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-9761103678571565692013-02-08T13:23:00.000-08:002013-02-08T13:26:20.936-08:00Planetary NebulasPlanetary nebulas are one of my favorite objects in the sky to observe. The way they look, and the way they respond to magnification, make them unique among the different types of nebula.<br />
<br />
<img src="http://upload.wikimedia.org/wikipedia/commons/6/64/M97.jpg" alt="The Owl Nebula, M-97" height="290" width="400" /><h5>The Owl Nebula doesn't look so dramatic in my telescope as in this image, but it's still one of my favorite objects in the sky.</h5><br />
<b style="color:#00ff77;">Nebulas</b><br />
Nebulas, or, more properly, <i>nebulae</i>, are cloudy-looking objects in the sky. The word <tt>nebula</tt> is Latin for 'mist', 'cloud', or 'fog'. There are a lot of different types of things that look like a patch of cloud or fog in the sky. To give a brief list, there are reflection nebulas, emission nebulas, supernova remnants, and planetary nebulas. Each is different, and looks like a bit of cloud in a modest sized telescope. Even galaxies were once considered nebulas, before it was discovered how far away they are, and that they're made of stars like the Milky Way.<br />
<br />
Planetary nebulas were given their name by William Herschel. He was trying to build a fairly comprehensive catalog of things in the night sky that aren't stars. He included a description of them in the <a href="http://books.google.com/books?id=IU9FAAAAcAAJ&pg=PA213&dq=philosophical+transactions+of+the+royal+society+%22volume+75%22&source=gbs_toc_r&cad=4">Philosphical Transactions of the Royal Society, Volume 75</a> starting on page 263. You can read it, without pestering your local reference librarian, thanks to Google Books.<br />
<br />
He chose the name because, though he knew they were nebulas, he also noticed that they tended to be somewhat round and that when magnified their brightness across their visible surface they tended to act like the illuminated disk of a planet, rather than like the other nebulas he had been observing. Sometimes it's implied that the name was given out of a mistaken sense that the objects have something to do with planets, but that's clearly not the case.<br />
<br />
<b style="color:#00ff77;">Stellar Remnants</b><br />
<br />
Today, we know that planetary nebulas are made up of material that's been cast off a star when it goes from being a giant star (like a red giant) to being a white dwarf star. When this happens, the outer parts of the star that aren't involved in the nuclear reaction of the star (which happens at the core of a normal star) are blown off into space by bursts of energy from the core. The core collapses to form the white dwarf, the outer areas of the star, usually called the "atmosphere", though it's nothing like our atmosphere except that it happens to be the outer part of the star just as the atmosphere is outside the solid and liquid part of the Earth.<br />
<br />
There are two basic types of planetary nebula, spherical and bipolar. The spherical ones appear to be stars that have blown off their atmosphere in a fairly uniform fashion.<br />
<br />
<img src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Abell_39.jpg/480px-Abell_39.jpg" alt="Abell 39, a classic example of a spherical planetary nebula." /><br />
<h5>Abell 39 is a perfect example of a spherical planetary nebula.</h5><br />
Bipolar planetary nebulas are ones where the material appears to be spread into two halves on opposite sides of the original star. Usually, each side looks like a mirror of the other half. One of the mysteries of planetary nebulas is why this happens, and how some of these beautiful forms come into being.<br />
<br />
<img src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e8/M27_-_Dumbbell_Nebula.jpg/476px-M27_-_Dumbbell_Nebula.jpg" alt="The Dumbbell Nebula, M-27" /><br />
<h5>One of the brightest bipolar nebulas in the sky, the Dumbbell Nebula.</h5><br />
The bipolar nebulas appear to take on a wide range of shapes. In some cases, probably in many of these cases, the nebulas themselves are the same shape as each other, but look very different when seen from different angles. Dr. Bruce Balick has a <a href="http://www.astro.washington.edu/users/balick/WFPC2/">great web page</a> on this that includes lots of other information about planetary nebulas.<br />
<br />
<b style="color:#00ff77;">Seeing Planetary Nebulas for Yourself</b><br />
<br />
Many planetary nebulas are bright enough to be seen easily. A few can be seen by eye, but they don't look as spectacular that way. The Helix Nebula is the closest known planetary nebula, and it can be seen by eye about 1/3 of the size of the Moon (when I look at it, it actually looks closer to half the size of the Moon, but that's probably just an optical illusion.) But it's very dim, because its light is spread out over such a large area. It looks more like a slightly light patch of sky than like a nebula.<br />
<br />
<img src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Iridescent_Glory_of_Nearby_Helix_Nebula.jpg/480px-Iridescent_Glory_of_Nearby_Helix_Nebula.jpg" alt="The Helix Nebula, a nearby planetary" /><br />
<h5>The Helix Nebula is visible by eye but it's not this dramatic and colorful.</h5><br />
Binoculars do a great job of bringing it out and making it look brighter. You still won't see what the Hubble Telescope sees, but it will be worth your while.<br />
<br />
A modest sized telescope will bring out detail in about another one or two dozen planetary nebulas in the sky. The Dumbbell, above, shows its "apple core" shape to even a small telescope at low magnifications.<br />
<br />
<b style="color:#00ff77;">The Future of Our Sun</b><br />
<br />
Present thought is that our own sun will create a planetary nebula of its own in the far future, several billion years from now. First it will become a red giant by puffing up its outer parts, then the core will collapse and the outer gases will be blown off into the space around it.<br />
<br />
I've heard mixed predictions of whether the resulting planetary nebula would be visible from within the solar system. Since the Earth will be destroyed during the red giant phase of the Sun, unless a future project relocates it somewhere to move it outside the space that the Sun will swell up into as a red giant, it'll be pretty much an academic question, anyway.<br />
<br />
I recently gave a talk on Planetary Nebulas to the Nevada County Astronomers. You can see <a href="http://saundby.com/astronomy/pne2013/">the slides from my talk</a> on <a href="http://saundby.com/astronomy/">my website.</a>saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-22589073215249724352013-02-04T14:35:00.000-08:002013-02-04T14:35:42.003-08:00Dr. Stephen Robinson to Speak in Folsom, Feb 19<center><img src="http://spaceflight.nasa.gov/gallery/images/shuttle/sts-130/med/jsc2009e125141.jpg" alt="Dr. Stephen Robinson in a Shuttle cabin spacesuit" /></center><br />
Astronaut <a href="http://www.jsc.nasa.gov/Bios/htmlbios/robinson.html">Dr. Stephen Robinson</a> will be speaking at <a href="https://www.threestages.net/Online/default.asp?doWork::WScontent::loadArticle=Load&BOparam::WScontent::loadArticle::article_id=62561E7C-B023-42E5-95B4-6769A3FA87C7">Three Stages</a> at <a href="https://www.threestages.net/">Folsom Lake College</a> on Tuesday, February 19th. He's the veteran of four flights on the Space Shuttle, including the Return to Flight mission of the Discovery, and one of the final missions in ISS assembly aboard the Endeavour.<br />
<br />
He's logged over 48 days in space on those missions, and over 20 hours of time spent on space walks.<br />
<br />
He's also somewhat of a "local", he completed his undergraduate work at UC Davis, and did his graduate study at Stanford.<br />
<br />
I'm sure this will be a very interesting talk, and it's not every day we get an astronaut out this way to give a presentation, so I recommend you <a href="https://www.threestages.net/Online/default.asp?doWork::WScontent::loadArticle=Load&BOparam::WScontent::loadArticle::article_id=62561E7C-B023-42E5-95B4-6769A3FA87C7">check it out!</a>saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-24235950025581390612012-11-28T10:02:00.003-08:002012-11-28T14:53:51.892-08:00Cloudy Skies Astronomy: RadioEach year the clouds move in during fall, before the clear, cold nights of winter. Each year I lay aside active astronomy for reading and other pursuits. But, I also think about picking up radio astronomy to "see" through the clouds.<br />
<br />
I haven't been a victim of the clouds every year. For three years when I was a teen, I actually did some radio astronomy. I had a short wave radio receiver, and I built new antennas for it each year. I started with a simple wire-wound antenna, using magnet wire wrapped around a fiberglass pole from a bicycle safety flag. It picked up the sound of electrical discharges between Jupiter and Io. The next year I made a simple dipole, which was a bit more directional, especially since the Earth and my apartment building blocked signals from two directions pretty well. But the apex of my experiments was the same dipole the next year.<br />
<br />
I trimmed its length to let it catch the frequencies I wanted more precisely in my high school's electronics lab. I didn't have any of the tools for that at home. Then I made a rickety "corner reflector" for it out of chicken wire and 2x2 lumber.<br />
<br />
With it I was able to catch the sounds of Jupiter and some other strong astronomical radio sources much more clearly. The background static was much reduced, and there was more detail to the sound, in fact, it started to sound like sounds rather than lightning discharges on an AM radio. I used this same get-up to catch some radio noises from Earth's own atmosphere, too.<br />
<br />
The results were enough that I've stayed interested in doing radio astronomy ever since, though I haven't done anything practical about it. But I sure think about it, every time the clouds move in.<br />
<br />
<center><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_rYL0m5ZF-njHQREQHB4RCtr8UcLcUCw7atoKUYn3cckAOlAsg3QzFDCL8K6LXwvq5S2qecdCywlb2yPDp8he0kuBsuanmT5jtyVJlrIgu9p1eXP_OA35z3LioVtkddaB9K0iWDB9fA/s481/satdish.jpg" alt="simple satellite dish antenna" /></center>If you're more motivated than I am to actually do something, here are some links that may interest you:<br />
<br />
Some great projects using satellite TV dishes as antennas:<br />
<a href="http://www.nrao.edu/epo/amateur/">NRAO Information for Amateur Radio Astronomers</a><br />
<br />
Jupiter and Other Simple Starter Projects:<br />
<a href="http://www.spaceacademy.net.au/spacelab/projects/jovrad/jovrad.htm">Detect Radio Emissions from Jupiter</a><br />
<a href="http://www.stargazing.net/mas/radio2.htm">Small Amateur Radio Telescope</a><br />
<br />
More projects from the U.K.:<br />
<a href="http://www.ukaranet.org.uk/uk_amateurs/index.html">UK Amateur Radio Astronomy</a><br />
<br />
A book, with some thick crunchy bits, that I recall reading back when I was getting started:<br />
<a href="archive.org/details/RadioAstronomyForAmateurs">Radio Astronomy for Amateurs</a><br />
<br />
And more fun stuff:<br />
<a href="http://www.signalone.com/radioastronomy/telescope/">Radio Astronomy Projects</a><br />
<a href="http://www.radiosky.com/project.html">Radiosky Radio Astronomy Projects</a><br />
<br />
This year I'll probably be distracted by "chasing DX" in amateur radio. I got my license last year, and I've only recently made my first contacts on the "HF" bands (short wave radio, basically.) But I may see if I can tune in Jupiter along the way.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-19058918198236435262012-08-10T04:40:00.000-07:002012-08-10T04:40:10.141-07:00How Big is a ConstellationOne of the most difficult things many people find in stargazing is learning the constellations. Most people can find Orion, and the "Big Dipper" here in the northern hemisphere, which pretty well passes for Ursa Major (the Big Bear.)<br />
<br />
But others are more difficult.<br />
<br />
Most constellations are not as well defined as the most popular ones. The three stars of Orion's belt are not only bright, but they're all about the same brightness. Which makes them easier to pick out. Then, finding the other bright stars of the body isn't that hard. Most folks don't bother picking out the stars of the head, shield, and so on.<br />
<br />
The Big Dipper is an asterism (sort of a non-official constellation, the words asterism and constellation mean the same thing but they're used differently.) It is made up of seven stars of roughly equal brightness that stand out from the background of the sky around them.<br />
<br />
But other constellations don't have nice patterns like this, with groups of stars of roughly equal brightness that are also brighter than other stars in the area, and with a nice fairly dark buffer space between them and the next constellation over.<br />
<br />
Another thing that makes it hard to find constellations, even when you use a star chart, is having a sense of how large they appear in the sky.<br />
<br />
Some are very large and spread out. Scorpius has a tail that stretches off across the sky. Ophiuschus, the Snake Handler, covers a large area next to Scorpius, along with the Snake he's holding. But the Fox and the Arrow are small.<br />
<br />
<b style="color:#ff7700;">Start With What You Know</b><br />
<br />
Before wandering too far out into unfamiliar territory, it usually helps to start with the constellations you know. That way, you already have a sense of where something is in the sky, and a general idea of what its boundaries are. Knowing more there can help, too. If there is a constellation you already know, compare the version of it you recognise in the sky with the version of it on the star charts. Are there large parts of it you aren't counting in when you see it? Where does it begin and end?<br />
<br />
Then, starting there, and considering the orientation (which changes over time), can you find some other constellation next to it from the chart?<br />
<br />
If you've already taught yourself to find the legs of the Big Bear coming off the Big Dipper, and the nose of the bear, then you're prepared to find the Hunting Dogs, a pair of stars beneath the curve of the Big Bear's tail. It's not much of a constellation, just a pair of stars, visually, but it is another constellation.<br />
<br />
Likewise, knowing both the Big Dipper and the Little Dipper, there's that line of stars running along between them. Those belong to Draco, the Dragon.<br />
<br />
Further south, once you've found the limits of Orion's limbs, you can easily find the Rabbit beneath his feet. And the Big Dog to one side of him, with the bright Dog Star, Sirius, in it.<br />
<br />
Pushing out your knowledge step-by-step in this way is a good way to learn constellations, because you can learn how to locate them again later, in a month or two, when the position of the constellations in the sky has changed.<br />
<br />
<b style="color:#ff7700;">Further Afield</b><br />
<br />
There are a few constellations that look like what they're named for. Scorpius is one of them. The bright red star Antares makes it easy to pick out in a July/August sky, with the head and claws nearby in a nearly straight line of stars that, while not all that bright, are easy to associate with each other because they're about the same brightness.<br />
<br />
From those, the Scorpion runs back through bright red-orange Antares then sweeps around in a long fish hook shape with a sort of barb on the end. (This constellation is Maui's Fish Hook to the Pacific Islanders.) A constellation that looks like its name, with a bright, distinctive star in it makes a good starting point when not working off a familiar constellation's side.<br />
<br />
Then, once it is learned, other nearby constellations can be learned.<br />
<br />
<b style="color:#ff7700;">The Power of Asterisms</b><br />
<br />
Just as the Big Dipper isn't an official constellation, but just a part of the Big Bear, there are other asterisms in the sky. Asterisms are more commonly named for what they look like than the traditional constellations. And many of them make up enough of the actual constellation they're part of that finding the asterism is about as good as saying you've found the constellation itself.<br />
<br />
The Teapot is an asterism that occupies the main part of Sagittarius, the Archer. The Teapot shape is not hard to see once it "pops" for you. If you hold your hand out at arm's length but bend it so that it's at about a right angle to your arm, it will about cover the area of the Teapot. The Teapot lives behind the tail of the Scorpion.<br />
<br />
It has a narrow right triangle as a spout, with the cloudiness of the Milky Way looking like steam coming from the spout. The body is a large trapezoid, which shares one side with the spout. On top (it's upside-down in the southern hemisphere) is a triangle of stars that's just a bit flat of an equilateral triangle which forms the lid of the Teapot. Finally, the handle is another trapezoid which is short and wide, with its bottom the side of the body that's opposite the spout.<br />
<br />
If you're in mid-northern latitudes it will be in the south near the horizon during summer.<br />
<br />
There are other asterisms like the Summer and Winter Triangles (the names are northern hemisphere centric) where each of the stars in the triangle is in a different constellation. By learning to find these, you get a foothold into three constellations apiece!<br />
<br />
The Winter Triangle has a star in Orion, the other stars are in the Big Dog (Sirius, the brightest star) and the Little Dog (Procyon, the dimmest star in the Triangle.)<br />
<br />
The Summer Triangle has a star in the Harp, the Swan, and the Eagle. Vega, in the Harp, is the brightest star. Deneb is a middling-bright star in the Swan, at the tail of the constellation (another constellation that has a resemblance to its name.) Altair is a bright yellow star in the Eagle. It forms one end of a pair of much smaller triangles that make up the wings of the Eagle.<br />
<br />
<b style="color:#ff7700;">Looking Gets You There</b><br />
<br />
It's not easy to learn your way around, unless you have somebody who's patient, already knows their way around, and there's a green laser pointer for them to use. Even at that, once the sky moves over the course of a few weeks, you will need to get re-oriented. But once you take the time to learn on your own, or through a guide, you will be able to star expanding on what you know quickly.<br />
<br />
Just as it's easier to find your way to more places around town, the more places you already know and can use as waypoints, you can find your way around more of the sky for each constellation you add to your personal list.<br />
<br />
Pretty soon the individual ones you know that are away from each other start growing into ones you know that run into other groups of constellations you know. Then you're looking at the areas in the middle of the constellations you know and wondering what those stars are. Whole sections of the sky become familiar.<br />
<br />
Learning the constellations is satisfying and enjoyable in and of itself. I still spend most of my time under the sky with no telescope or binoculars or other "distractions". But the side benefit is that once you do take out an instrument, you can now easily find many items to look at if you know at least a handful of the current constellations in the sky. Some of the best things to look at are placed in easy to aim at places in the constellations. Or, if you have a computerized telescope, you can more easily and more surely give it its guide stars to get its computer started off.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-44374155395345186322012-07-11T14:34:00.001-07:002012-07-11T14:34:54.873-07:00Hot Summer Solar ObservationOur community holds a celebration each year to one side or the other of the Fourth of July. We have a street fair, dachshund races, parade, and, usually, fireworks. Lots of locals like it because it lets them extend their Fourth of July celebration a bit and get in some extra fireworks each year.<br />
<br />
<a href="http://thecomethunter.com/">Don Machholz</a> organizes the local astronomers to take part in the street fair, where we take out our telescopes and show off the sky, as much as we are able, to the local community. We enjoy sharing our hobby, as well as letting them know about the other events we have going on.<br />
<br />
Each year we have several solar telescopes out, as well as <a href="http://astrobasics.blogspot.com/2009/07/daytime-observing-with-your-telesccope.html">viewing planets in the daytime</a> when the conditions are right.<br />
<br />
Last year we weren't able to attend, but the year before that we were there, showing the sun and explaining to people that <i>usually</i> there are things to see there other than a featureless circle. But a featureless circle was about all we had to show. There was a bit of unimpressive detail through the H-alpha filters, but chances are most of the attendees that looked didn't get so far as noticing it.<br />
<br />
This year was a great change for the better. There were sunspots, and prominences. Sunspots are nice since they show up in an ordinary telescope with a solar filter. We had a scope with a solar filter, plus a solar projection screen that both showed the sunspots very nicely. Viewers compared them to the islands of Hawaii.<br />
<br />
Through the H-alpha filters there were a bunch of prominences around the edge of the Sun. Solar flares, if you will. They change with time, each lasting several hours or longer and changing their appearance over that time.<br />
<br />
<b style="color:#ff7700;">Why the Difference?</b><br />
<br />
A normal solar filter shows all the different visible frequencies of light. All it does is cut the amount of light down to a level where it doesn't damage our eyes or the telescope. It's what we'd see if we could stand to look straight at the Sun and still make out any detail. Plus the telescope provides magnification that makes it look larger so that we can pick out small details more easily.<br />
<br />
An H-alpha filter is a filter that only lets through one wavelength of light, the light emitted by one type of ionized hydrogen (that's where the "H" in H-alpha comes from, H is the symbol for hydrogen). This light is in the red wavelength for us, so the image becomes a "red and white" (as opposed to black and white) monochrome image.<br />
<br />
This clears out other light frequencies that smear out or otherwise hide a lot of interesting detail on the Sun. In H-alpha light we can see the magnetic cells of the Sun. These cells are not like the cells in our bodies, the word cell originally meant "chamber" so it got used wherever early scientists saw things divided up into little "rooms" or "chambers".<br />
<br />
It also allows us to see the energetic material being ejected, and pulled back into the Sun. Normally the other light hides these flares and loops and other prominences. But in H-alpha light, the other light is blocked out, allowing us to see these interesting solar features.<br />
<br />
<b style="color:#ff7700;">A Good Show, Again</b><br />
<br />
So now we have a good show on the Sun again. This is likely to be the case for at least the next couple of years. Usually there are only one or two years out of each solar cycle (an 11 or 22 year period, depending on how you look at it) where the Sun isn't putting on a show. And the quiet period we're coming out of was far quieter and longer than any other I've ever experienced.<br />
<br />
Which is nice. It's a lot easier to get people interested in what's going on "up there" when you've got something interesting to show them.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-8336490248109446462012-06-06T16:57:00.000-07:002012-06-06T16:57:53.540-07:00Transits of VenusHopefully you had the chance to see the transit of Venus yesterday (5th or 6th of June, depending on where you were). A <i>transit</i>, in astronomy, is when one body (usually a planet) passes between another body and the Sun. In this case, the planet Venus was directly between the Earth and the Sun. Another example might be when the planet Earth goes directly between Mars and the Sun. This would be a transit of Earth to the rovers on Mars.<br />
<br />
<tt><a href="http://astrobasics.blogspot.com/2011/10/phases-of-venus.html">Observing Venus</a></tt><br />
<br />
<center><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFDNhQX9yaXIpzK3ge0wN2f-hSpckhpYZAoT78LwwURiJZx-Nh-Q2U47yV2jXV0N5hKNzYXKNYjq9M7LP_0vh8nrjRt25iOqBWQbrHYqepZjWCAxYGar_fey8bfXsR9CEaRFhv5UsxEg/s480/projected-Venus-transit-m.jpg" alt="Image of Venus Transit of the Sun" /><h5>Projected Image of Venus Transit from a Telescope run by George Robinson at the Auburn Dam Overlook in California.</h5></center><br />
Here on Earth we only have two planets to come between us and the Sun, Venus and Mercury. The Moon comes between us and the Sun, too, and those are solar eclipses, an even very similar to a transit (it wouldn't be totally inappropriate to call it a Lunar transit.)<br />
<br />
<b style="color:#ff7700;">Why is it Special?</b><br />
You'd think this would happen all the time. After all, since Venus and Mercury are within the orbit of the Earth, and orbit the Sun in less time than we do, it seems like they'd always be crossing between us and the Sun. The thing is, those planets have orbits that aren't perfectly flat compared to ours. If their orbits were flat compared to the Earth's, then we would see them cross the face of the Sun every time they were at "inferior conjunction", that is, as close to us as they get in their orbit. ("Superior conjunction" is when they're on the far side of the Sun from us.)<br />
<br />
But their orbits are tilted. That means that they need to be in a part of their orbit that is in line with our orbit at the same time that they are at inferior conjunction. With planet Mercury, this happens a bit more frequently than once every ten years or so. Since Mercury's orbital time is so much shorter than our own, there are many more opportunities for things to line up like this than with Venus.<br />
<br />
<tt><a href="http://astrobasics.blogspot.com/2011/10/viewing-planet-mercury.html">Observing Mercury</a><br />
<br />
With Venus, this sort of line-up only occurs a couple of times over the course of a bit over a century. For these last two occasions, those times were separated by eight years, leaving 105 years until the next line-up.<br />
<br />
<b style="color:#ff7700;">How It Looked</b><br />
Yesterday was the first transit of Venus I've seen. I missed the last one because I wasn't in a position to travel at the time it occurred. I've seen transits of Mercury, so I thought I knew pretty well what to expect. I expected pretty much the same thing, with Venus a bit larger against the surface of the Sun.<br />
<br />
In fact, it was a lot different. For one thing, Venus was a lot larger against the Sun than I expected. It was also a much crisper image, sharply defined at the edges, compared to Mercury. Mercury looked kind of fuzzy, like heat waves were around the edges. Venus was large enough that the edges didn't look this way.<br />
<br />
We got to see it through several different telescopes, including two with H-alpha filters that let you see the prominences and solar flares on the Sun. One clever set-up from our friend Larry had a pair of binoculars rubber-banded to a piece of two by four lumber, with a cardboard sun screen, and the image from one of the two binocular lenses projected onto a paper plate at the other end of the two by four. The assembly was supported by the rungs of an overturned stool, which could be turned several ways to get different heights.<br />
<center><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMPvYHgj-Dkujt6YEwjzgZjaqbGVDAO_z1ETJ0fpkzxc3vW4hxtjyt67QAV6KGpMInu2NN2597Sm3F0jfgLksUJFGVIT6dMbXahCAsbiqW_DCffMF_ar7-DJn18G1pjh6_PIqIZyM_IQ/s480/Larrys-Solar-Observatory-m.jpg" alt="Simple Solar Observing Set Up, Viewing Venus transit." /><h5>Larry, the master of laid-back astronomy, brought this portable solar observatory along with his 8" Dobsonian telescope.</h5></center><br />
As much as I enjoyed looking at various magnified images, I was most impressed by looking at the Sun directly through a pair of solar filter glasses. The circle of Venus was easy to pick out (Mercury isn't), and it looked a bit eerie just hanging there in the sky in front of the Sun.<br />
<br />
It will be a long time until we can see another transit of Venus on Earth (105 years), but there will be a transit of Mercury in 2016, and spaceflight offers more opportunities for viewing transits off of Earth. Hopefully by the time of the next Venus transit, viewing transits of the planets won't be limited to the Earth and low Earth orbit.<br />
<br />
A good article on why transits happen as infrequently as they do is at <a href="http://www.skyandtelescope.com/observing/home/152556885.html">Sky and Telescope</a>.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-51963076685271848932012-04-14T02:19:00.002-07:002012-04-14T02:27:19.350-07:00Stargazing: Looking to SeeWhether you're using your eyes or a telescope or binoculars, it takes time to see everything you can see.<br /><br />To see the most, pick details out of faint contrast, or simply enjoy the view takes enough time to relax a bit and soak it in.<br /><br />That means you have to be able to spend some time doing it. Which is not possible if you're uncomfortable, you or any instruments aren't stable, and if you just don't take the time.<br /><br />There'll be more to see, and enjoy, in the sky if you give yourself the things you need. Time, comfortable clothing, a good, safe place to observe, well-chosen instruments with the right accessories for basic use, a place to stand, darkness.<br /><br />It sounds obvious, but I know I've talked myself out of one or more of these at various occasions. I doubt I'm alone.<br /><br />Dark skies and good seeing.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-4571657886633074272012-03-06T14:59:00.003-08:002012-03-06T15:17:36.144-08:00Seeing Mars in 2012We're near our <a href="http://astrobasics.blogspot.com/2012/01/observing-mars.html">opposition</a> with Mars as I write this (March 2012), an event that comes every 26 month, approximately. This year, we're going to have a Mars in our sky at night for many months:<br /><br /><ul><li>March: up all night. Size: 13 to 14 arc seconds. Brightness: magnitude -1.0!</li><br /><li>April: up till about 3:30am. Size: 10 to 13 arc seconds. Brightness: magnitude -0.35!</li><br /><li>May: up till about 2am. Size: about 9 arc seconds. Brightness: magnitude 0.26.</li><br /><li>June: up till about midnight. Size: about 7 arc seconds. Brightness: magnitude 0.7.</li><br /><li>July: up till about 11pm. Size: about 6 arc seconds. Brightness: magnitude 1.</li></ul><br /><br />As you can see, Mars will be bright and fairly good sized for much of the year. However, in July Mars will be less than half the size it is in March. That means it will take over twice the magnification to get a comparable level of detail. But it will be dimmer, too. So the closer to the opposition you view, the better view you'll get. The fact is, magnification will not make up for the smaller size of Mars.<br /><br />But Mars will still be putting on a good show, even this summer when it will be nice and warm out at night.<br /><br /><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgOKbF3ANDjySA04mDtFe3NuwVj3MOfxSqk855R-IZJ1ZvXDpbFJScNrIEJB286_X8mZ-Sx-nxxsTgkr1QtAnCjYgMVXj3PfxKPsbSCAV2MKLNa-s-HA5PMp1_GYLlmZa9CepDy7Wf3L4M/s466/Mars_transparent.png" alt="Mars" />saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com2tag:blogger.com,1999:blog-5645593341528211288.post-85380484806041226172012-01-24T14:47:00.001-08:002012-03-06T14:59:43.726-08:00Observing MarsMars is getting close to its "opposition". That's the best time to observe Mars, generally (depending on conditions otherwise.) That's because that's when Mars is closest to Earth, and it is its brightest.<br /><br /><center><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyawVqnUpv6s5yhSk1JXOO6AXp5wckd1t-5i-D13YwcI0tknuAxzZ5uN4kXl0zmiqppxPIe5WFk1NqZFZbTFrwl9N9eyz-swu5wkwSS_voHh4GYCCXxI0XQzUr8Kni2W8L2NcdVpBbmDE/s305/Mars.jpg" alt="Image by amateur astronomer Arnomane of Wikimedia" /><h6>Image by <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyawVqnUpv6s5yhSk1JXOO6AXp5wckd1t-5i-D13YwcI0tknuAxzZ5uN4kXl0zmiqppxPIe5WFk1NqZFZbTFrwl9N9eyz-swu5wkwSS_voHh4GYCCXxI0XQzUr8Kni2W8L2NcdVpBbmDE/s305/Mars.jpg">Arnomane</a></h6></center><br />That also means that Mars is at its largest, as viewed from Earth. Oppositions occur roughly once every two years. This time, Mars will be <a href="http://elvis.rowan.edu/marswatch/opposition.php">about 13.9 arcseconds across</a>, at a distance about 1.66 times the distance to the Sun. For comparison, the Moon is about half a degree across, or just about 30 arcminutes. Each arc minute is sixty arc seconds. That means that the Moon is about 1800 arcseconds across.<br /><br />The Moon is large enough to see a fair amount of detail by eye. But to our eyes, Mars appears only as a bright dot, even at its largest. The minimum angular resolution of the human eye is about 1 arc minute, or 60 arc seconds. Mars would have to be over four times larger for us to see it as anything other than a dot by eye. It certainly never gets <a href="http://www.badastronomy.com/bad/news/">as large as the Moon</a>! This is known as the <a href="http://www.badastronomy.com/bad/news/marsattacks2005.html">Mars Hoax</a>, an internet hoax that's been going around, and around, and around on the internet for about nine years now. It just can't look that big!<br /><br /><b style="color:#ff7700;">Make It Bigger</b><br /><br />Since we can't see a lot of detail by eye, we use magnification to see the detail of Mars's surface. At the low magnifications of ordinary binoculars (7x to 20x), Mars shows as a small disk, but little or no detail is visible. A stable mount and higher levels of magnification are needed, which means that a telescope is the best instrument for observing Mars.<br /><br />Mars will begin to show details at about 35-50 powers of magnification. This is low magnification for your telescope. At this level large things like the polar ice caps and Syrtis Major (pronounced like "Sir Tiss Major"), a large dark area on Mar's surface, become visible. To see more details requires increased magnification.<br /><br />How much magnification you can use will depend on the observing conditions, the quality of your scope's mount and tracking, and your experience in astronomical observation. Mars is a good object to learn with. It's bright, it has both strong and subtle details. If you want to get good at using higher powers (over about 150-200x) on your telescope, this is a great opportunity.<br /><br />For myself, I do my detailed observation at about 350-400x. At this level I find I can get the most detail with my 8" Newtonian telescope without it being a strain to track Mars with my scope, or having to break off my observation too often. Larger telescopes, and <a href="http://www.stellarvue.com/">very well made refractors</a> with good mounts will be able to use higher powers, but for most observers with little high power experience, anything over about 200x will be challenging.<br /><br /><b style="color:#ff7700;">Now in Living Color!</b><br /><br />To tease out the finest details of Mars, it can be very beneficial to use colored filters. I have two sets of colored filters that I use for general observation. Dim objects don't work well with filters because the filter cuts off too much light to leave a bright enough image to see. Fortunately, Mars is quite bright.<br /><br />I observe Mars with all the different colors of filter, but I find the red and yellow color filters to bring out the most unique detail. A blue filter is often worth observing with, it brings out polar caps and clouds on Mars. Yellow and orange filters bring out details, usually better than a red filter. <br /><br />There are no hard and fast rules I've found in my own observation of Mars with colored filters. Different viewing conditions and different seasons on Mars each have an effect on what will be seen. So I usually cycle through all of them in an evening, then go back to those that brought out the most unique detail.<br /><br /><b style="color:#ff7700;">Take a Picture, It'll Last Longer</b><br /><br />To really teach yourself to see detail, try doing sketches of Mars at the eyepiece. I draw several circles on a sheet of paper ahead of time for the outline of the planet (or just print out a sheet with circles about 2" in diameter on it), then sketch in basic light and dark areas with a normal pencil.<br /><br />I then take notes of the time, date, magnification, and any filters that I am using. I make sketches with each of the different filters that I find work well on Mars during that observing session.<br /><br />When I'm observing without a filter, I make notes on the colors of the details and try to fix them in my mind. Later, when I'm inside with light, I color in areas of my sketch with colored pencils to try to capture the colors, or color differences, that I saw on Mars.<br /><br />Drawing Mars really helps you to learn to see the details on Mars. It also gives you a personal record of what you saw. You can go to the internet with the time that you saw Mars, or to your favorite astronomy program, and look up Mars's orientation at the time you drew it. Compare what you find with what you drew. It will never look the same, but you can see a match between different parts of your drawing and the image of Mars as it was when you drew it. Going back later, you may see other details that you didn't capture in your drawing.<br /><br />At which point it's time to start another drawing. :)saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-37122199455165076202012-01-14T07:30:00.000-08:002012-01-14T07:30:00.438-08:00Cold Weather Astronomy: Be Prepared!In my <a href="http://astrobasics.blogspot.com/2012/01/winter-observing.html">prior article</a> I discussed ways of staying warm and safe while observing in the cold by controlling your location and taking advantage of what's nearby. In this article I'll discuss personal preparation and protection from the cold.<br /><br /><b style="color:#ff7700;">Fashion Sense and Sensibility</b><br /><br />Obviously clothing is an important part of staying warm when out stargazing in winter. Having the right clothes for the conditions is critical. When it's really cold, it's not something you can fake easily with substitutions. Proper winter wear that protects both your core temperature and your extremities is critical.<br /><br /><b style="color:#ff7700;">Humidity Good and Bad</b><br /><br />Even though the humidity high in the sky is very low, thanks to the cold conditions, the humidity levels at ground level can be quite different. If it's at all damp where you are, this can make it feel far colder than the temperature would suggest. Also, as the evening cools this dampness can condense on you and freeze as well. So any clothing used must protect against moisture.<br /><br />While humidity outside your clothes can be a problem, inside your clothing it's part of keeping yourself warm. Clothing that helps trap your body's moisture to some degree helps keep you warm. The colder it is, the more your clothing should confine the moisture.<br /><br /><b style="color:#ff7700;">The Layered Look</b><br /><br />Layers of clothing are important, both to provide redundant levels of protection from the cold and to serve different purposes. Clothing worn near the skin should be porous and absorbent to keep moisture from collecting on the skin, which can chill. It also allows the warm air trapped within your outer clothing to circulate some to better distribute your body's heat.<br /><br />The next layer out should be chosen for warmth, and should also breath some. Wools and acrylics are good choices, as they will keep you warm no matter what the level of moisture.<br /><br />The outer layer should prevent wind from getting in and your body's heat and moisture from getting out.<br /><br /><b style="color:#ff7700;">Easily Freezable Bits</b><br />Hands, feet, ears, and other outer parts of your body deserve special attention. They freeze easily, and are easier to forget when a particularly nice bit of galactic detail swims into view.<br /><br />Heated socks and gloves are available, and heated hats. Some use batteries and heating elements, others use chemical packs to generate warmth. In my case I've found aluminized clothing to work just as well. I have aluminized socks and glove liners that I wear in cold weather. They work so well they literally feel as if they are electrically heated.<br /><br />For example, I usually wear the following on my feet:<br /><ul><li>Inner cotton socks</li><br /><li>Acrylic knee-high socks</li><br /><li>Aluminized socks</li><br /><li>Outer wool or thick cotton socks</li></ul><br /><br />I have a loose pair of older leather boots that I wear in winter to accommodate these layers of socks.<br /><br />On my head I wear a balaclava under a heavy winter hat.<br /><br />On my hands I wear a pair of cotton-lined aluminized gloves, with a pair of leather "police inspection" gloves outside of them. These aren't quite enough to protect my hands on the coldest nights, but I use these because it still leaves me enough dexterity to handle eyepieces and focusers. I put my hands inside heavy pockets when I'm not actually handling things, or use an outer pair of heavy mittens if I'm not going to use the pockets or if the pockets just don't stay warm enough.<br /><br /><b style="color:#ff7700;">Internal Preparation</b><br /><br />Before going out into the cold, it's important to be well fed. Don't go out hungry, it leaves your body with insufficient reserves to keep you warm, and keep you alert enough to notice if you're getting too cold to be safe.<br /><br />I usually plan a warm meal with a warm drink before going out. I also keep something warm to drink, and a high calorie snack available for observing breaks. If at all possible, these breaks should be taken in a warm place.<br /><br /><b style="color:#ff7700;">Breaks and Self-Inspections</b><br />Plan to have breaks in your observing sessions. They should be long enough to let you warm up completely. You need to be able to tell if parts of you are getting too cold, or if you're having trouble making decisions clearly. I do a bit of observation logging during my warm-up sessions to give me something to do while warming.<br /><br />When outside, and when inside, perform a self-inspection to see if any part of yourself is getting cold and numb. Frostbite is not a necessary part of astronomy. Check your fingers and toes for flexibility and feeling. Check your ears, nose, chin, scalp, elbows and knees. Poke your calves and forearms while you're at it. Blink your eyes and make sure any cloudiness blinks away. Touch any exposed skin to make sure it's still there.<br /><br /><b style="color:#ff7700;">Two Ways to Err</b><br />It's possible to make mistakes in either of two ways: being too gung-ho and ending up regretting an observing session that goes too long or that you get too cold. It's also possible to miss out on some of the best observing time of the year by being too timid and hiding from the cold when the proper location and dress would be all it takes to have an enjoyable time under the sky.<br /><br />Don't miss out on winter observing, and don't over-do it, either!<br /><br />Plus, if you have any personal tips or tricks you use, please share them in the comments.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-30855543069276530732012-01-07T11:04:00.000-08:002012-01-07T11:04:00.190-08:00Keeping Warm When Observing in Winter<a href="http://astrobasics.blogspot.com/2012/01/winter-observing.html">Winter skies</a> can be some of the best of the year. But it's hard to enjoy them if you're not safe and comfortable while observing. Cold air may being doing something wonderful for the skies above, but there are lowly land-level things to take into consideration.<br /><br /><b style="color:#ff7700;">Losing Sky to Gain Warmth</b><br />Where you observe can have a lot of effect on the conditions. Open areas far from buildings and trees are the best for views of the sky, but they are usually the coldest as well. Ground level temperatures at night are strongly affected by radiation of heat from the ground. When the area has a clear view of the sky, it radiates its daytime heat more readily into the sky, cooling more and faster than if it has partial cover.<br /><br />If it's just plain too cold to enjoy the sky from a completely open area, observing the sky from one or more sites that have some partial cover can save the evening. It can be several degrees warmer in a location that has partial tree cover. Buildings keep the areas immediately next to them warmer as well. If you are viewing in a direction away from the building, any air currents caused by heat coming off the top if the building can be avoided.<br /><br />By choosing partially covered locations well, you can move from place to place and be able to observe all or most of the sky without being quite so cold.<br /><br /><br /><b style="color:#ff7700;">Cover the Cold Ground</b><br />Observing atop a non-porous ground cover helps significantly as well. A tarp or sheet of painter's plastic makes a good ground cover. Something else thrown on top of the ground cover will help keep the site even warmer. An old blanket, chunk of carpet, or some other form of insulating material on top of a ground cover will help make the observing site far more comfortable.<br /><br /><b style="color:#ff7700;">Wind</b><br />If there is any wind, some form of wind block will obviously be helpful to staying warmer. For foliage and sizable structures, you'll usually get the best protection on the downwind side of it. For smaller or erected wind breaks, the best protection may be on the downwind side but in many cases will be on the upwind side. In these instances a dead zone forms in the upwind area, whereas the downwind side may actually be colder due to air flow caused by the low pressure area formed on the downwind side. Be prepared to try both. This can also occur with some building layouts, but is more common with small wind screens, fences, and the like.<br /><br /><b style="color:#ff7700;">Slippery Slopes</b><br />Sloping ground can also be colder than flat areas. Convection along the sloping surface can make for a drifting draft that chills astronomers. At my prior home we lived on a slope just beneath a ridge line. Our weather was far colder than many other places at our elevation. We would have snow at times when the properties around us were clear. Our location gave us a great view of the sky, but it was colder.<br /><br />In one corner of our property there was a dell with less of a view of the sky, but warmer air tended to pool there for some reason (I'd have expected it to be colder.) But I noticed that snow appeared there later than anywhere else nearby. Once snow <i>got</i> in there it stayed later than anywhere around because it received little sunlight. But at night, it was one of the warmest places to be, thanks to low airflow, partial tree cover, and a thick bed of leaves on the ground.<br /><br />It's also important to be in a safe place to stand and move around a bit in the dark. Our present property has a steep section above a cut. It happens to give the best views to the north and east, but most of it isn't safe to traverse at night without light and extreme care. For this reason, I avoid it. Falls and injuries are a bad way to end an observing session. And it doesn't get you any warmer.<br /><br /><b style="color:#ff7700;">Warm Up Shack</b><br />Having a nearby location where you can take breaks from observing and warm up is a good idea. My number one observing location is at home, but I also travel to nearby locations that give a better view than my home. At the very least, I have my car as a place to go for breaks. I keep both a wool blanket or sleeping bag and a space blanket on hand. I run the engine for the heater while inside, and put a piece of cardboard on the dash to block the lights to preserve my night vision.<br /><br />I keep some high calorie snacks in there, and a thermos of something warm to drink when I've though ahead that far (boy, I regret it when I don't!)<br /><br />A car isn't the best warm-up shack, and a club site or other prepared observing location can have a dark warm-up room that allows you to duck in for a while to warm up, count your appendages, and generally decide whether to continue your time under the sky in warmth and comfort without having to wait half an hour for your night vision to fully return just because you wanted to get in out of the cold for a bit.<br /><br />At home, I work with my family to choose a door I can go in and out of to a darkened area. That makes it easier for me to come in every so often without having my night vision ruined every time I do. Usually I keep my log and a red LED light there, I'll update my log while I'm warming up and possibly think of some more things I can look at if I go back out.<br /><br />Having something to do when I first come in makes it easier for me to wait the time it takes to get warm enough to make a reasonable decision about whether I should go back out, and to keep me from rushing back out before I'm really completely warmed up. Not being able to feel your feet isn't a good sign, but it's one I've missed at times when I didn't make sure I got warmed up properly before going back out (fortunately the warming was enough that I did get sharp pains about ten minutes after going back out, rather than just numbness. That hint I did catch!)<br /><br /><b style="color:#ff7700;">Prepare Yourself</b><br /><br />In the next article I'll discuss what you can do in the way of clothing and self-preparation to make winter observing more enjoyable.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-48278194050738421222012-01-01T12:18:00.000-08:002012-01-01T12:31:44.902-08:00Winter ObservingThis time of year is winter for us in the northern hemisphere. It's one of my favorite times for observing. Both with telescopes and with my eyes or binoculars. Even if it's nothing more than lingering in the driveway to enjoy the sky for a few minutes after a drive home, the clarity of the sky makes the stars stand out with the best contrast of any time of the year.<br /><br />Winter brings cold, but on clear nights that cold makes the sky especially clear. The upper level cold freezes out moisture in the air. It's a perfect time of year for looking at faint fuzzies. If you have a smaller instrument, this is a great time to see things that are fainter than you can normally expect to find when the humidity is higher.<br /><br />I have started many of my personal observing programs during this time of year, including seeing how many galaxies I could see with 7x35 binoculars, learning my way around the deep sky north of 70 degrees with a 75mm reflector, and seeing how close of doubles I could pick out by eye. The sharp appearance of the sky makes winter the perfect time to start new observing objectives.<br /><br />With larger instruments, this is still a good time to view objects that are challenging, or to see more detail in familiar objects, like picking out more detail in galaxies.<br /><br />Whether you're using your eyes or a light bucket, now is the perfect time to get out and enjoy sharp, high contrast skies. While the clouds are away, let the cold air freeze out the atmospheric humidity so that you can get the best views.<br /><br />Stay warm with layered clothing, good socks, and good gloves.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-50499374342440279042011-11-11T06:04:00.000-08:002011-11-11T06:04:01.215-08:00Observing the EarthOne of the easiest planets to observe is our own, the Earth.<br /><br />It is possible to view the Earth as an "astronomical object", in a way, even though you're standing on it. One way is to view your local daily cycle of night and day as it appears on other planets and the Moon--becoming aware of the terminator as it passes by twice each day.<br /><br />Another is to enjoy the events of the Earth's own sky. Clouds, colors of sunlight, meteors, and auroras are all Earth phenomena that we can enjoy as astronomers. The play of light on clouds, especially at sunset and sunrise, is not only beautiful but can tell us what the sky is going to be like in the next several hours. <br /><br />Meteors can be seen on most any clear night, preferably with little moonlight. The best scientific instrument for watching meteors is a reclining lawn chair, such as a chaise lounge. Meteor showers occur regularly, but even when there are none there are a fair few meteors, and I've spent nights under the sky where I was <i>sure</i> there must be a shower, there were so many meteors, when there was none.<br /><br />Auroras are rare at my latitude, but that makes them an even more special phenomenon. Whether I go to where they are, or whether the Sun's activity brings them to me. They're amazing and magical.<br /><br />Even when I can't see the universe beyond our own atmosphere, there are clouds and often lightning to see. No night need be a "wasted" night. And if you really must observe the universe, consider making a simple radio telescope!saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-21340672835102058032011-10-30T05:41:00.000-07:002011-10-30T05:41:00.101-07:00The Phases of VenusVenus is the second planet from the Sun, and makes for a satisfying viewing target. Though it is covered with clouds at all times, it is not devoid of detail.<br /><br />The planet Venus shows phases, like the Moon. In fact, the most common comment I hear when showing Venus through my telescope is "It looks like the Moon!"<br /><br />During the daytime, it can be seen as a ghostly moon-like object. It takes great care to keep the telescope from viewing the Sun. If this can be managed, Venus shows up well during the day. The trick is to position the telescope away from the Sun, on the same side of the Sun as Venus, by using the shadows on the telescope <i>without</i> looking through the scope (and probably covering the end of the scope to keep the sunlight out!) Then, once you're sure there's no Sun in the scope, look through and sweep <i>away</i> from the Sun. Practice sweeping in the correct direction <i>before</i> your eyeball is at the scope.<br /><br />At night, you don't have to worry about this. If anything, you may find Venus is a bit too bright. A color filter or neutral density filter can help cut the light down a bit to make it more comfortable to view. Careful and patient use of a variable polarity filter can reveal murky details in the clouds of Venus.<br /><br />Venus shows a full set of phases, from new and thin crescent phases to a Full Venus.<br /><br />It can be a lot of fun to watch Venus from week to week as its phases change. It goes much more slowly than the Moon, overall, but there are some phases that seem to shoot past, and others (like full) that seem to last forever.<br /><br />Ordinary binoculars won't show the phases clearly, but when Venus is away from "full" it'll sure look like something's wrong. Crescent phases can take on all sorts of interesting shapes in binoculars, sometimes looking like a line, other times looking just mis-shapen.<br /><br />For the early Greeks, Venus has two names depending on whether it was a morning star or an evening star. As a morning star it was Phosporus, it was called Hesperus as an evening star. In the sixth century B.C. Pythagoras recognized it as a single object, which was named Aphrodite and later given the Roman name Venus as the goddess analogous to Aphrodite.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-57630304585148679322011-10-23T05:29:00.000-07:002011-10-23T05:29:00.187-07:00Viewing Planet MercuryPlanet Mercury is the closest planet to the Sun. Its orbit around the Sun is entirely within the orbit of the Earth. This means that from our point of view, Mercury always appears in the sky near the Sun. Sometimes it is seen setting in the evening shortly after the Sun sets, other times it is seen in the morning just before the Sun rises. At other times it is invisible, lost in the Sun's glare.<br /><br />The early Greeks had two names for Mercury, depending on whether it was seen as a morning star or an evening star. As a morning star it was Apollo, as an evening star it was Hermes. It was later recognized to be a single object, and the name Hermes, the messenger of the gods, was the precursor to the Roman name Mercury that we use today.<br /><br />Mercury can be seen by eye as a medium-bright red-orange star near the Sun. Binoculars will show that it's not a star, but a very small disk-like shape that looks un-star-like. It looks much the same in a telescope, though under good conditions it will show a "phase" like one of the Moon's phases, most commonly a crescent, since it is usually seen when well away from the Sun. It doesn't show any detail in telescopes, it just appears as a small reddish-orange shape, its shade of color varies some because of Earth's atmosphere.<br /><br />At times it moves very quickly across the sky. Its position relative to the Sun, and to the stars in the sky, can be seen to change rapidly from day to day. It makes an interesting project to keep track of Mercury's position in the sky on a star chart over the course of a month or two.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-83068488152046151962011-08-05T12:24:00.000-07:002011-10-16T17:28:50.321-07:00Learning the ConstellationsLearning your way around the sky at night is a matter of learning to see some of the patterns in the stars so that you can pick out particular stars, and have an idea of where other stars are with respect to them. It's a piecemeal process that takes a bit of time, but is very rewarding.<br /><br /><b style="color:#ff7700;">One Step At a Time</b><br /><br />Don't expect to learn a lot of constellations all at once, or, if you do, don't expect it all to stick. Part of the challenge is that the constellations change their place in the sky all the time, and that the ones that are visible will vary by the season.<br /><br />Because of this, if you learn some constellations tonight, then come back out under the sky in a few weeks, the constellations will have moved. As the Earth goes around the Sun in its orbit, the constellations up at a particular time of night will change a bit and those that stay up will appear to have moved in the sky. They will also change their orientation, so the stars that were on the bottom are now on the side.<br /><br />Don't be discouraged. Learn the stars by relative positions. Turn yourself and your body around to see the patterns you've memorized. Where possible, get out often to see them before they've changed beyond recognition.<br /><br /><b style="color:#ff7700;">Season's Greetings</b><br />Since different stars are up in the early evening at different times of the year, it's also useful to divide the constellations you know by the season you see them. For myself, The Archer, The Scorpion, The Snake-Handler, and The Virgin are summer constellations. Orion, the Big Dog, Small Dog, and Gemini are winter constellations. Perseus the Hero, Andromeda, and Pegasus are spring constellations. <br /><br />When I see one of these, I think of the others and locate them in the sky by the one I see first. In fact, these constellations are not just visible in the season I think of them belonging to, but that's when I learned them, and that's when I know I can see them on a clear night with a good view of the sky around me. It breaks up the job of learning what's where.<br /><br /><b style="color:#ff7700;">High and Low</b><br />It's often easiest to locate new constellations when they are either near the horizon in some direction, or at the highest point in the sky. The ones that are in-between often seem to be harder to get a handle on, unless they have some special feature that makes them easier to see as a constellation, like the Big Bear's seven stars of the Big Dipper that are all about the same brightness in the same part of the sky.<br /><br />With a star chart for the time of year you're out, and the time of night, you can see what should be near the horizon in any given direction as well as what should be directly overhead. Pick out particularly bright stars on the chart to use as guides. Then find other bright stars on the chart, and locate them with respect to the first one you found. Then look at the less bright stars, and get them placed with the constellation they belong to. After a while, you should be able to see the "picture" of the constellation in the sky.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-70298487444594466562011-07-12T16:55:00.000-07:002011-07-12T17:41:18.710-07:00Wine Tasting Under the StarsIf you haven't had a chance to enjoy a star party, either as an astronomer or an attendee, I highly recommend going to one. Chances are there are astronomers in your area who hold regular star parties. In my fairly remote area, there are at least three groups running star parties on a regular basis.<br /><br /><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWi9qu8hAzN1jO2vIsm0sSLXyhCfw55FJJwQmMl-QaaUb4Ks66bxhx_lazA0kl-it3Wk6p_6piH-R9Wy8uJo6gEu6liI0VGDnCeGo5MmzecM0nBomHX4rxZ6r2twZOgrc10VVSW0Go5SM/" style="width:450px ; height:300px;" /><br /><br />One of the star parties I helped organize this year was at a local vineyard. They combined our star party with a wine-tasting and music event at their site. We did this star party at <a href="http://www.davidgirardvineyards.com/">David Girard Vineyards</a>, in <a href="http://www.coloma.com/">Coloma</a>, California.<br /><br />We had six different telescopes out at this event (the sixth arrived after these pictures were taken.) Attendees got to see a wide variety of astronomical objects through the scopes while enjoying wines, cheeses, and so on. It was a very nice event for everyone.<br /><br /><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRTj9U_TpqDCEWQRyG_K2fs57W62KF2V952UwR_mPjueCZYqQzYA22WM42_OcgevVkHnSrIKt46WZg1kqvag1VW7SyM-HNvcY7RCu4mrkeNLidPe-zTr1kyVmpj6YMs2L-3GNqY0Fc8QU/" style="width:450px ; height:300px;" /><br /><br />Attendees got to see the heavens not only through the astronomer's telescopes, but with their eyes alone on green-laser guided tours of the constellations. Green laser pointers are used because the beam itself is visible at night, so it can be used to point things out under the real sky just as effectively as a planetarium lecturer can point things out in their dome.<br /><br />The astronomers who chose to partake of the wines got to enjoy those while showing the skies, and we all enjoy sharing our hobby and knowledge with an appreciative audience. When I spoke to the other astronomers afterward (there's usually little chance for us to talk among ourselves while during the event itself), we all felt like the time had gone by amazingly quickly. This is a good sign that everything was going well, and that we all had lots of interested attendees to show the sights in the skies.<br /><br />For at least one of our astronomers, this was their first time showing the sky to the public. It's a great experience, no matter what your skill level is in astronomy. There are always a few basic, easy to find objects you can show off at a star party. So long as you're familiar with your equipment and it's in good enough shape that you don't have to fiddle with it constantly, you're ready to do star parties.<br /><br /><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLK9b64tLPl0UKnJ-UEPA6HnxbsOJ4hCnst9vklQ9IZm3K1zEex8vtU3RYDIFrTT_bQdwWg6wj11Hd-PmS4MLKZ-Dn4zX70CV0JoqNb5QPRS7uahyaR6Tx_u9KAgxvyeW_QHX9AQYmt4E/" style="width:450px ; height:300px;" /><br /><br />I've been sharing the skies myself for over 40 years now. It started without any doing on my part. I got my first telescope when I was very young. I'd set it up on our front lawn to look at the Moon and stars while I was learning my way around the sky and my new telescope. This was during the heat of the space race, in the 1960s. People driving by on the street would see me with the telescope, stop their cars, and come have me show them things through my telescope.<br /><br />For many people it was the first time they'd actually seen craters on the Moon with their own eyes. Even objects as simple as bright stars would interest them, even if I didn't know the name or constellation yet.<br /><br />Their questions got me to learn more about what I was looking at. They'd ask me where the Surveyors and Rangers were on the Moon (Apollo hadn't landed yet.) That made me learn my way around the Moon with a map from National Geographic magazine that showed the locations of the probes, as well as the selected Apollo landing sites. I memorized them and that allowed me to answer the questions about the Moon. Similarly, I learned the names and constellations of the brightest stars, which was much harder since I really didn't know my way around the sky, yet.<br /><br /><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWNEsTo9AnACd6T6Q56eczPtxuGH_7p-Wn9sv71d4ORzFsaFb1ntS7edyIGSeKbsvQ_yWiZf0xBOQQCWTECTeTDfXwZ9q2zSd1PY0acwonNzagvnW38JGT9xN-HzwrogkFMZJveWyJoxM/" style="width:450px ; height:300px;" /><br /><br />The breakthrough came when I learned from a copy of Sky and Telescope in the library that the correct way to use a star chart is to hold it over your head. Just as you hold a map of the ground down low, and align it with the Earth, you hold a sky map over your head, and align it with the sky by putting it's north to your north.<br /><br />If you are an amateur astronomer, find or organize a local star party. You'll find it improves your appreciation of your hobby in too many ways to list. If you're just interested in astronomy, find one to attend and enjoy. It's like having not just one telescope of your own but a whole bunch of self-pointing, self-maintaining telescopes to enjoy the heavens through.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-40934844124552082902011-06-14T09:25:00.000-07:002011-06-14T10:21:17.127-07:00Double StarsAbout half of all the stars in our galaxy are part of a multiple star system. Either a binary star, triple star, or a larger group of stars. The stars are bound to each other by their mutual gravity so that they orbit each other. This puts them close enough to each other that we see them together in the sky.<br /><br />In some cases the stars are of different types or sizes, so they make a striking pair when you look at them through telescope or binoculars. With half the stars in our galaxy being in multi-star systems, these pairs can be found all over the sky. I've found that the colors in stars are different through different sized scopes, certain colors are more intense with different diameters of scope. So it's interesting to look at the same pair of stars through different scopes on the same night to see how they look through each.<br /><br /><b>Albireo</b><br /><br />Visually, Albireo is the star at the head of Cygnus the Swan. It's easy to see most of the year in northern latitudes. Through binoculars or telescopes the colors of the stars make for a striking contrast. One star appears as blue or white, depending on the night and your instrument. The other ranges from a deep amber or orange to a fair yellow. Whenever we're at a star party, if my wife hears that Albireo is in somebody's scope, she rushes over for a look at this celestial gem.<br /><br /><center><img src="http://upload.wikimedia.org/wikipedia/commons/f/f5/NewAlbireo.jpg" alt="Albireo, a beautiful double star. Image by Hewholooks." /><h5>Albireo, image by Hewholooks</h5></center><br /><br />Use low magnification (<100x) on Albireo if you're using a telescope. You might want to take a second look at a medium level of magnification (about 100x) to see if there's a color change at this level.<br /><br /><b>Cor Caroli</b><br /><br />Cor Caroli, "Charles' Heart", is what folks usually expect to see when you say "double star". The stars are of very different brightness, and it takes just a bit of effort to see the dimmer star in the glow of the brighter star. Low magnification will reveal the dimmer star, I usually show this star at 40x. Medium levels of magnification will make it easier to pick out the companion, but will tend to make the difference in brightness not as strong.<br /><br /><center><img src="http://upload.wikimedia.org/wikipedia/commons/8/84/Cor_Caroli_2011-03-01.jpeg" alt="Cor Caroli, in Canes Venatici." /><h5>Cor Caroli</h5></center><br /><br />Visually, Cor Caroli is the brightest star in Canes Venatici, under the curve of the Big Dipper's handle. It's visible year-round in northern latitudes.<br /><br /><b>Algeiba</b><br /><br />Algieba, or Gamma Leonis, is another pair with fine color. It's part of the backwards question-mark that forms the head and chest of Leo the Lion. It's the lower star in the back of the curl of the question mark.<br /><br /><center><img src="http://upload.wikimedia.org/wikipedia/commons/2/21/Algieba_binocolo.png" alt="Algieba, in Leo, a beautifully multi-colored double star." /><h5>Algieba, image by Roberto Mura</h5></center><br /><br />Binoculars will reveal the double, but I prefer to view it at low powers in a telescope.<br /><br /><b>Omega Scorpii</b><br /><br />This is another blue-yellow pair in Scorpius, just a bit toward the head of the Scorpion from the northern claw. It's visible from both northern and southern hemispheres.<br /><br /><center><img src="http://upload.wikimedia.org/wikipedia/commons/f/ff/Omega_Scorpii_binocolo.png" alt="Omega 1 and Omega 2 Scorpii." /><h5>Omega 1 and Omega 2 Scorpii, image by Roberto Mura</h5></center><br /><br />This pair is widely separated, almost as much as the width of the Moon. View at low magnifications, or with binoculars. The entire area of sky around them is magnificent through binoculars.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-75874691181163518562011-03-20T21:58:00.000-07:002011-03-21T13:20:12.181-07:00Rainy NightsWhen the weather doesn't allow observation, what do you do?<br /><br />1. Tune Up the Telescope.<br /><br />Give it a once-over. Check the optics, check the lubrication on the focuser, make sure there are spare batteries for the red dot or Telrad finder, plus any other battery powered equipment in the accessories box. Organize and clean up the observing stuff in general.<br /><br />2. Go Over the Observation Logs.<br /><br />I've kept logs of my observation since I was 14 years old. I don't still have all of them, and I don't write a log every time I go out under the sky. But I appreciate it later when I do have logs from earlier years. On cloud cover nights, I can review them and reorganize them as necessary.<br /><br />By going back over them, I can see objects that were particularly nice to observe that I may have forgotten about, or want another look at (once the sky clears.) I can see objects that I missed in the past that I never got back to. I can see some prior "records" I've set for most deep sky objects in a night, or most planets, satellites, or whatever.<br /><br />All this gives me further inspiration for future observations. Some of my best observing sessions were planned on an overcast night spent with my logs.<br /><br />3. Prepare for Future Observations<br /><br />I've spent time learning new constellations, planning star-hops to new objects, and reading lists of objects (like double stars with interesting colors) in preparation for nights when I can get out and see stars.<br /><br />I use software to learn constellations (Deep Space on my Amiga computer was really good for this back when), modern software packages can do this, too. Turn off the constellation lines and names, move the sky around a bit, make your best guesses in the part of the sky you can see, then turn on the lines and names and see how close you got.<br /><br />I also visit the online sky surveys to see what something is going to look like. First I visit objects I know to see how they compare to how they look in my telescope. Then I go to new objects to get an idea of what to expect. Sometimes things don't always look the way you expect, and sometimes you have more than one deep sky object (galaxy, nebula, star cluster) in one area, and you need to tell them apart.<br /><br />4. Build a New Accessory<br /><br />Once the scope and all are in good shape, chances are there's something else you'd like to have. This is a good time to make it, or go shopping for it if that's your preference.<br /><br />5. Take Up Radio Astronomy<br /><br />After a particularly long period of overcast, I once got so frustrated that I decided to take a first stab at radio astronomy. If I couldn't see light, I'd catch <i>something</i> that could get through the clouds. After considering and rejecting the idea of making a lens out of paraffin wax (which refracts some radio frequencies) I decided instead to do something a lot easier. <br /><br />I made a simple <a href="http://www.qsl.net/ve3rgw/corner.html">corner reflector antenna</a>. I put together a simple wooden frame (two triangles with sticks connecting them at the corners into a prism shape.) Then I put metallic screen across the back on two sides, and suspended a short dipole antenna across the front (two pieces of wire tied together in the middle by an insulator. I think it was kite string.)<br /><br />Then I ran this to my short wave radio and hooked it up to the antenna screws on the back. I pointed it at where I supposed Jupiter to be, and after about three hours of messing around I heard radio signal from Jupiter, something like the shots of static from thunderstorms, but different. I kept the reflector around for a while, and showed it off to some friends once the sky cleared (it was a lot easier to point when I could <i>see</i> Jupiter).<br /><br />Since then I have set up radio receivers to hear meteors and receive amateur radio "moonbounce" communications. All pretty easy stuff.<br /><br />On occasion, I have considered drumming up a pair of old "big dish" satellite TV antennas and tying them together into a very small array. But the sky usually clears before I get very far. :)saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-57381636905182735572010-09-21T12:37:00.000-07:002011-10-16T17:16:53.974-07:00Is It a Planet, or Not?Just as the word "<a href="http://astrobasics.blogspot.com/2010/08/what-is-galaxy-anyway.html">galaxy</a>" has changed its meaning through time, the word "planet" has changed from meaning one thing to another.<br /><br />Our present, somewhat muddy, view of what "planet" means has been created by our current perception of the universe. Without this perception, our definition becomes meaningless. The way our view of "planet" has changed since the word was invented is the result of continuous 'updating' of the meaning to make it match our current views.<br /><br /><b style="color:#0077ff;">The Original Planets</b><br /><br />The word planet was originally used to describe something that moves across the sky independent of the motion of the stars. The stars all moved together, their position with respect to each other never appeared to change. It was as if they were all attached to some big sphere with Earth in the middle. But there were seven objects up there that moved around on their own (other than objects like clouds, meteors, and comets which were considered transient phenomena, rather than objects.) They wandered around, and didn't move like they were fixed in place like the stars.<br /><br />Because they wandered, they got the name "planetes" from the Green word for "wanderer" (root <i>plan-</i>). So a "planet" was something that was seen to wander across the sky. The planets were:<br /><ol style="color:#dddd00;"><li>The Sun</li><br /><li>The Moon</li><br /><li>Jupiter</li><br /><li>Venus</li><br /><li>Saturn</li><br /><li>Mars</li><br /><li>Mercury</li></ol><br />Notice that the Earth was <i>not</i> a planet. What a laughable idea! The Earth's not in the sky. But notice that the Sun <i>is</i> a planet. Of course, it is in the sky, and it moves independently of the stars.<br /><br />The fact that there were seven planets tied heavily into the perception of seven as some sort of special number. There were seven known metals, after all, and each was associated with one of the planets (gold, silver, copper, tin, lead, iron, and mercury.) Sevens were found all over the place, in part because of the number seven being tied to the planets. It was an early attempt at identifying unifying rules behind the universe.<br /><br />One that the ancients appear to have missed is the planet Uranus. It is actually bright enough at times to be seen by eye. But it appears as most as a very dim star, and its motion against the other stars is slow enough it would not have stood out as easily at the other planets.<br /><br />Also, there were times when Venus was thought to be two planets. Its appearance in the morning, on one side of the Sun was thought to be one planet, called Phosphoros, and its appearance in the evening another, called Hesperos. Pythagorus of Samos recognised it as a single object, which became known as Aphrodite as the knowledge spread through Greek culture. It had been known as a single object long before, by the Mediterranean cultures, but for a time Greek culture saw it as two objects. Later, when the Romans adopted Greek astronomy, they translated Aphrodite to their own goddess, Venus, which is the name we use today.<br /><br /><b style="color:#0077ff;">The Sun-Centered Universe</b><br /><br />After the word planet had become well established, a new way of looking at the universe came about. Originally, there were two places that defined the universe, Earth and Sky. While the idea that the Sun may be a more central place to the universe than Earth goes back long before Copernicus, it was still something remote and "out there" rather than "down here", so the idea of Earth as having more kinship with Mars and Venus than the Sun never really took off. They were all "out there."<br /><br />But with the general acceptance of the Copernican concept of calculating the calendar by the motions of objects circling the Sun, the Earth became one of those objects circling the Sun. There was no general word for "things that circle the Sun", but five of those things were already called planets, the sixth circled an object that circled the Sun (the Moon) and the seventh was the Sun itself.<br /><br />Plus, everything associated with the rejected idea of things going around the Earth was ready for disuse. Why not just repurpose some of the terms? Like, say, "planet."<br /><br />Planet was redefined as "things that circle around the Sun." Now the Sun was no longer a planet, and neither was the Moon, since it didn't directly circle the Sun, but the Earth. But Earth joined the new short list of six planets.<br /><br />Later, when Galileo found little objects circling Jupiter he gave them a name appropriate for little things hovering around the King of the Gods, he called them "attendants", or, as the word he used has come to us, "satellites". This gave a new category for the Moon to fall into, it now became Earth's "satellite."<br /><br />Later, more objects were found to be circling the Sun. They, too, were planets, as the definition of "planet" was "something that circles the Sun." They were defined as planets by their motion around the Sun. This included Uranus and a bunch of small objects between Mars and Jupiter, in the wide gap where Bode's Law said there ought to be a planet.<br /><br /><center><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqwXqvYcvoc2OKo2xDbRkEI2LHD3Y4IMVYJKdPcVUklI8u8WRY5NGrXSnpNAxBgbt2u2NoMLGxtu6pS5nkeDIQKInGpzEzzABqq3zeRoqKezqJVi613BnZYOsYlo5OY8YWOVhAqRHCac0/" alt="Orbits of planets from the Sun to Jupiter, including Ceres, Pallas, Clio, Aethra, and Medusa." /><h5>Planetary Orbits from Recreations in Astronomy, 1886</h5></center><br />These objects were located by their motion. They were dim, but they moved independently of the "fixed stars", and their motion was described as "planetary". That is, they were moving around the Sun.<br /><br />It wasn't too long before about 200 of these objects were found. To help keep track of them, they were given numbers as well as names. Some special ones were found that weren't in orbits in the space between Mars and Jupiter, like Eros. Eros has an orbit that goes from outside the orbit of Mars to inside it, nearing Earth. For a long time Eros was the object known to come closest to the Earth, aside from the Moon.<br /><br /><b style="color:#0077ff;">Are Asteroids Planets?</b><br /><br />In the astronomy books from the time of the discovery of Ceres and Pallas, up to the 1930s, the asteroids are usually given, as a group, the same treatment as any other single planet. In the chapter or chapters detailing the planets of the solar system, the asteroids appear among the other planets.<br /><br />In the 1869 tenth edition of <u>Outlines of Astronomy</u> by Sir John Herschel the asteroids are described definitely as planets. He acknowledges that very little is known about them, and that assertions that some of them possess an atmosphere is highly questionable. But he does speculate for a moment about possible life on these small planets:<br /><blockquote style="padding:15px; background-color:#ffffcc; color:#472000;"><p>"On such planets giants might exist; and those enormous animals, which on earth require the buoyant power of water to counteract their weight, might there be denizens of land."</p><p>-Sir John Herschel, 1869</p></blockquote><br /><br />He defines them as planets thus:<br /><blockquote style="padding:15px; background-color:#ffffcc; color:#472000;"><p>"The sun and moon are not the only celestial objects which appear to have a motion independent of that by which the great constellation of the heavens is daily carried round the earth. Among the stars are several...which...are found to change their relative positions among the rest...These are called <i>planets</i>. [Of those discovered since 1800] all of them but Neptune belong to a peculiar and very remarkable class or family of planets to which the name Asteroids has been assigned."</p><p>-Sir John Herschel, 1869</p></blockquote><br /><br /><u>Recreations in Astronomy</u>, 1886, by Rev. H.W. Warren has an extensive chapter on the asteroids, as complete as any of the sections dedicated to the other members of the solar system. In it he describes:<br /><br /><blockquote style="padding:15px; background-color:#ffffcc; color:#472000;"><p>"...Piazzi, an Italian astronomer of Palermo, found in Taurus a star behaving like a planet. In six weeks it was lost in the rays of the sun. It was rediscovered on its emergence, and named Ceres. In March, 1802, a second planet was discovered by Olbers in the same gap between Mars and Jupiter, and named Pallas."<br /></p><p>-Rev. H.W. Warren, 1886</p></blockquote><br />The "star behaving like a planet" part is the source of the name "asteroid", which means "star-like". Through the telescope the asteroids do not show a disk, as do most of the planets. They show only a star-like point of light.<br /><br />In Dr. Charles Young's <u>Lessons in Astronomy</u> of 1896, the planets are divided between the "Inferior" planets and "Superior" planets. The inferior planets are those whose orbits are inside the Earth's, the superior those that orbit outside the Earth's path. The asteroids have a section equal to that of the other planets, bearing the title "The Asteroids, or Minor Planets". Minor in this case means "small", rather than "unimportant." Dr. Young is very comprehensive in his discussion of the solar system, including even the Zodiacal Light with its own section among the planets, as opposed to among the sections discussing comets and meteors.<br /><br /><center><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiNodl95HwqktECDDtUjM-kLiIXdaLvlVwcfVyggm_kQliSH2Uv5iHpjaM3sdpa4uFYJYaB321p60mJkWSUaJt5IbdqU9W3KN8_Dbfbmg_xfnNg54cxIHQEE5cMFonymj7v8i0k3_1UG08/s640/sunfromplanets.jpg" alt="Relative size of the Sun as seen from different planets, including planets Flora and Mnemosyne." /><h5>The Sun, as Seen from Planets Flora and Mnemosyne</h5></center><br />In Dr. Simon Newcomb's <u>Elements of Astronomy</u> from 1900, they have a section like that of the other planets. The asteroid Eros rates its own section, because of the unusual nature of its orbit.<br /><br />Fellow of the Royal Society Richard A. Procter ignores the existence of the minor planets entirely in his 1901 book <u>Other Worlds Than Ours</u>. His book's focus is mostly on the possible habitability of other worlds, so he not only ignores the asteroids, but throws Venus and Mercury together into a single chapter on "The Inferior Planets", while Mars, Jupiter and Saturn each rate their own extensive chapter. Uranus and Neptune share a chapter as "The Arctic Planets." Meteors and Comets even get their own chapter, looking at their influence on the formation of the solar system. But the asteroids, clearly too small to be habitable, are left out.<br /><br />In 1923 Joseph McCabe refers briefly to the asteroids, not as planets, but as "planetoids." In <u>The Wonders of the Stars</u> he describes them as filling the space for a predicted planet between Mars and Jupiter, a planet which either broke up or failed to form.<br /><br /><b style="color:#0077ff;">Other Planets?</b><br /><br />Aside from the asteroids, it was thought that as many as four planets had been seen inside the orbit of Mercury. <u>Lessons in Astronomy</u> includes a brief section on Intra-Mercurial Planets, whereas <u>Recreations in Astronomy</u> goes a bit further by having a chapter on planet Vulcan. <br /><br />In both instances the case for planets inside Mercury are stated, and in both cases the lack of evidence leaves the author unconvinced of the presence of the planet(s). Dr. Young notes that the "planets" supposedly plotted during an eclipse, if plotted only slightly differently, are in the same position as known fixed stars.<br /><br /><br /><b style="color:#0077ff;">Pluto</b><br /><br />Upon its discovery, Pluto is first supposed to be the size of the Earth. Over time, its expected size has diminished. Its greatest perceived decrease in size came after the discovery of its moon, Charon. The presence of this moon allowed the mass of Pluto to be determined with some precision for the first time, using simple calculations based on gravity and laws of motion.<br /><br />Pluto was found to have a mass of about 2 thousandths of the mass of the Earth. In fact, much of the mass that Pluto was supposed to have turned out to be in its satellite, Charon. Charon has about 12% of Pluto's mass.<br /><br />Still, Pluto was an exciting discovery during a time when most of professional astronomy had shifted its attention outside the solar system to dealing with the stars and galaxies.<br /><br /><b style="color:#0077ff;">New Qualifications for Planets</b><br /><br />Before the discovery of Pluto, as the number of known Asteroids grew, it was suggested that perhaps the Asteroids should be excluded from the class of planet. Their small size and diminutive effect on the dynamics of the solar system were cited as reasons for removing them from the list of planets, as well as the desirability of keeping the list of planets brief enough to manage without a printed list.<br /><br />They were never entirely removed from the designation of planet, however. Their planetary motion, that of having independent orbits around the Sun, militated in their favor. Eventually they became known as Minor Planets, and in informal use were left off the accounting of the planets.<br /><br /><b style="color:#0077ff;">Xena/Eris</b><br /><br />The discovery of an object beyond Pluto which might prove to be larger than Pluto captured the public attention as the discovery of a "tenth planet." This object was given a working name of "Xena", which became popular. Later the official name "Eris" was applied to this object. To date, it does in fact appear to be larger than Pluto. Other objects have been found to be of similar size, though to date Eris and Pluto are the largest known objects in the solar system beyond Neptune.<br /><br />The discovery opened up a controversy about the definition of "planet" and the status of Pluto as a planet. Just as with the asteroids, the possibility, in fact probability, of numerous small objects like Pluto being found in the outer solar system had many questioning whether a new definition for the word "planet" should be made which would exclude these objects before they were added to the list of planets as the asteroids had been originally.<br /><br />In 2006 the International Astronomical Union decided to not only assign the name Eris to "Xena", but to formally redefine the term "planet" in such a way that Pluto and Eris (and several other sizeable objects, including the asteroid Ceres) were excluded from that definition.<br /><br /><b style="color:#0077ff;">The Third Step</b><br /><br />The first two requirements for the new definition of "planet" were uncontroversial. They are:<br /><ul><li>The object must be in orbit around the sun.</li><br /><li>The object must be massive enough to pull itself into a spherical shape.</li></ul><br /><br />The first requirement is the same as has been used since "planet" got redefined from "something that moves in the sky against the stars" to "something that orbits the sun."<br /><br />The second requirement is a new physical limit to set a lower size on what would be called a planet. It would formally exclude all but a few of the Minor Planets from the designation of "planet". Ceres would still qualify as a planet, but not as a "full member", rather than simply as one of the Minor Planets. Pluto would likewise retain its status under these two rules.<br /><br />But under the process the IAU followed, a third rule was added:<br /><ul><li>The object must have cleared the area around its orbit.</li></ul><br /><br />This rule, while unclear in many ways, had the effect of excluding any of the asteroids, Pluto, and any of the objects near or like Pluto.<br /><br /><b style="color:#0077ff;">Is This the Right Committee?</b><br /><br />The process for the decision was flawed in many ways. Initially, the committee within the IAU that was responsible for the decision about naming "Xena" and developing a definition for "planet" tried to communicate clearly before the conference where the votes would be held and prepare the attendees for the choices that would be placed before them. That was good, they worked in good faith to try and bring in the scientific community as much as possible.<br /><br />In the end, however, the choices that were presented ahead of time were set aside, and new ones were formulated at the last minute at the meeting, often going directly against the stated objectives of the working group itself. While no IAU rules were violated in this process, it ended up having a negative effect on the results. Community input was laid aside, many directly concerned scientists were unable to take part in the vote, and it limited what could be considered for the vote itself. A delay would have been better, though it would have meant putting off the decision, possibly for two years.<br /><br />The final votes were taken after many of the scientists who had expected to participate in the decision had left the conference. Most astronomical organizations can't afford to sent their scientists to the conference for its full duration. They plan to attend only on those days most important to them. They were there for the early votes on the plans that didn't pass, Most had left before the last day of the meeting, when the final vote and decision were made.<br /><br />Finally, it was not explicitly part of the IAU's charter to define the word "planet." They took this upon themselves to some degree. Not without reason, but consultation with the various national bodies from which they derive their powers, along with a higher level of public involvement, would have helped build a consensus for their decision to take this on in addition to their chartered tasks. It was their assigned job to name newly discovered objects, but not to determine what is, and is not, a planet by changing the definition.<br /><br />All of these factors, plus others which are political and bear on the funding models for scientific work, had the unfortunate effect of turning the decision into a very controversial one. So far, the decision has not been formally revisited, though it should be. Either the definition could be reworked to gain a greater level of acceptance both among scientists and the public, or the present definition or something close to it should be established through a process that allows for a far greater degree of inclusion and interaction both by the scientists involved in solar system studies and by the public.<br /><br />Before any further vote, the IAU needs to make its case that defining the word "planet" is even in its power, and that involved organizations outside the IAU accept that and any process it plans to use to formulate that definition. Educational groups and a variety of scientific organizations both in and outside astronomy, and government organization associated with science should be approached on this basis. The definition of "planet" affects far more people in society than astronomers.<br /><br /><b style="color:#0077ff;">Adding to the Controversy</b><br /><br />As if the problems with the 2006 IAU decision were not enough, the name chosen for objects which just fail the definition of "planet" on the third criterion were given the designation "dwarf planets." Why is this a problem? Because the noun applied to them is still "planet". A chihuahua may be a "small dog", but the adjective "small" doesn't remove it from the class of "dog."<br /><br />So, formally, that makes the "dwarf planets" actually planets according to the rules of English, at least. No matter that the IAU says on one hand "they're not planets", they then, confusingly, call them planets.<br /><br />By that light, we presently have 12 known planets in the solar system. In order from the Sun by average distance they are:<br /><ol><li>Mercury</li><br /><li>Venus</li><br /><li>Earth</li><br /><li>Mars</li><br /><li>Ceres</li><br /><li>Jupiter</li><br /><li>Saturn</li><br /><li>Uranus</li><br /><li>Neptune</li><br /><li>Pluto</li><br /><li>Haumea</li><br /><li>Makemake</li><br /><li>Eris</li></ol><br /><br /><b style="color:#0077ff;">Emotional Content</b><br /><br />With the controversy has come a range of emotional reactions on both sides of the debate. One is a false concern over how many planets there "ought" to be. The concern is that if all Plutoids are recognized as planets, then the list will grow too long for schoolchildren to memorize, or some other such vague upper limit that would seem to suggest that the number of planets is somehow important. Another is the use of the term "demoted" with respect to Pluto, suggesting that it is being punished, or its supporters for its definition as a planet are being punished by the act of redefining "planet."<br /><br />There are many other such things that get drawn in as well. On these two subjects, a clear answer to the first may be whether an upper limit should be placed on the number of U.S. Presidents or U.K. Sovereigns to make it easier to memorize their names? Perhaps we should redefine President to drop the one-termers, and Sovereign to consolidate those with the same name but different numbers, or otherwise simplify the list, perhaps by dropping those who ruled for less than a decade. Perhaps we need likewise limit the number of States in the U.S., the number of elements on the Periodic Table? All nonsense, of course.<br /><br /><b style="color:#0077ff;">Slice and Dice</b><br /><br />A reply to the second concern is that we can divide and distinguish the planets in different ways, choosing that which suits the task at hand. We have historically divided the planets in many different ways. There are the inferior and superior planets. There are the terrestrial and gas giant planets, now usually divided as terrestrial, gas giant, and ice giant. Plutoids is another designation that has been added, and though it appears to be a sop thrown to those who see Pluto as a planet, it can have a valuable use in naming large Kuiper belt objects like Pluto and Eris.<br /><br />Realistically, there isn't a good reason for creating an exclusive definition for the word planet beyond the first, and possibly the second, terms from the IAU decision of 2006. The only reason to do so that I can perceive have more to do with emotional satisfaction than science.<br /><br /><b style="color:#0077ff;">Other Words, Other Worlds</b><br /><br />We are at the point now of getting our first halfway decent look at objects smaller than suns outside our solar system. Many new terms are being coined to describe these objects. At this point, we're only capable of seeing certain types of objects well, though we're starting to get a look at a broader class of objects. The things we can see well are those which are very massive compared to the planets in our solar system, and which are in orbits with short periods, close to their sun.<br /><br />Hence we have "Super Jupiters" and "Hot Jupiters" and "Super-Earths" and many other types of planets being described. We are still looking for "Earths" outside our solar system, and one after another type of planet will be proclaimed an "Earth" or "Earth-like" planet as what we find draws closer and closer to the size, temperature, orbit, and other characteristics of the actual Earth. So far, we've seen the term applied to planets with several times the Earth's mass which are far hotter than Earth and closer to their sun. By the time an actual Earth-like planet is found, the public will be sick of hearing about a "new Earth" being discovered every few weeks.<br /><br />But the joy of these terms is that they are not determined by committee. No central ruling council is bothering to create a canon of terminology for these objects yet. The scientists engaged in the work are creating their own terms as an informal shorthand that allows them to avoid stating mass, average temperature, and orbital characteristics every time.<br /><br /><b style="color:#0077ff;">De-define Planet?</b><br /><br />Perhaps the course of discovery and description should be allowed to go its own way within the solar system as well as outside it? Once a bureaucracy takes a task on itself, can it be expected to relinquish that task, if the organization is supposed to be for the good of science?<br /><br />Maybe the scientific community, as a community, independent of the bureaucracy of the IAU, needs to take back its right to define terms appropriate to their own use. Some will see Pluto as a planet, others will not, depending on their perspective and their work. Perhaps the first error was forcing the issue to a formal vote by a committee.<br /><br />Or perhaps a new solution that works will be formulated and ratified through the same vote process, and the controversy will fade into the trivia of history.<br /><br /><b style="color:#0077ff;">New Data Changes Old Words, Again</b><br /><br />This seems likely, as the quantity of data that will affect our view of planets and solar systems that's coming from outside our own solar system will have its say soon. Just as the definition of planet changed decisively when our knowledge of the structure of the solar system changed due to Copernicus and Kepler, our knowledge of what a solar system is will soon change again.<br /><br />Chances are we're going to be using the word "planet" in a new way very soon.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-34517481729464692632010-08-30T14:38:00.000-07:002011-10-13T08:07:39.686-07:00The Collapsing Sun<i style="color: #00ff00; font-family: serif;">"Let my eyes look upon the Sun<br /> Until I have been filled with light!<br />Darkness leaves when there is sufficient light.<br />May I who am truly dead still behold <br /> the brilliance of the Sun!"</i><br /><tt style="color: #00ff00;">-Gilgamesh, The Epic of Gilgamesh, Tablet X</tt><br /><br />All life on Earth depends on the light and heat of the Sun, without it, we could not survive. It is natural that our nearest star is an object of study for science. The study of the Sun not only tells us about the Sun itself, but it informs and been informed by our study of our home, the Earth. At one point, scientists felt that they had determined the likely age of the Sun. But geologists found evidence that the Earth was older than the age of the Sun.<br /><br /><b style="color:#ff7700;">A Problem of Timing</b><br /><br />How could the Earth be older than the Sun? Especially when much of the geological evidence was the action of water and wind, both effects driven by the power of the Sun?<br /><br />Lord Kelvin brought his knowledge of physical science to the debate. The mass of the Sun was easy enough to determine. He calculated the possible age of the Sun based on the possible heat that he knew that mass could generate, and obtained a range of ages for the Sun, from 100 million to 40 million years. He felt the lower number was more likely, and later he gave even lower numbers for the likely age, down to about 10 million years. The science was simple, the calculations were brief and consistent with all known science.<br /><br /><b style="color:#ff7700;">What Heats the Sun?</b><br /><br />Central to Lord Kelvin's work was the way in which the Sun generates heat. In order to assess different ideas, some idea was needed of just how much heat the Sun does give off in the first place. A first estimate of this was possible after Herschel's experiments in 1838.<br /><br />He used an apparatus that sounds laughably amateur today, yet with it he managed to get the first measurement of the energy output of the Sun. He put a carefully measured amount of water amounting to about a cupful into a vessel very nearly like a tin cup. He put this inside a double walled tin vessel to exclude the heat radiated from everything else in the area, but had a three inch hole that would let through a ray of sunlight. He put a thermometer in the cup, and stirred the water to keep it all at as consistent a temperature as he could, then measured the temperature change as the Sun's light struck the cup over a measured time period. <br /><br />Using his data and some brain power, he produced figures that amounted to the Sun producing about 800 million calories of energy per second for every square meter of visible surface area. Later observations with better equipment brought this figure up even higher, to about 1.2 billion calories per square meter per second. What was the Sun doing to create all this energy?<br /><br />Let's look at the course that was taken to figure out the answer to this question. Even to early scientists, the question was intractable. Analogy with known means of incandescence and heating was tried first. The first attempts as scientific study of the Sun were attempted, but the results were vague:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"Two opinions, or theories, have been entertained in order to account for the production of heat and light by the sun; one supposes that the sun is an intensely-heated mass, which throws off its light and heat like an intensely-heated mass of iron: the other, based on the ground that heat is occasioned by the vibrations of an etherial fluid occupying all spaces, supposes that the sun may produce the phenomena of light and heat without waste of its temperature or substance, as a bell may constantly produce the phenomena of sound.<br /> Whatever may be the true theory, a series of experiments, made some years since by Arago, the eminent French astronomer...by examining the light which it affords...was found to be in the unpolarized or ordinary condition of light...from which proceeds this light proceeds must be in the gaseous state, or, in other words, in a state of flame. From other experiments and observations, Arago was led to the conclusion that the sun was a solid, opaque, non-luminous body, invested with an ocean of flame."<br /><tt>-Wells's Natural History, David A. Wells, 1861</tt></blockquote><br /><br />The concept of the Sun as a solid bovY seems strange today, but remember that the mass and size of the Sun were both well known. This means that the density of the Sun could easily be calculated, and that density was higher than that of any known gas or liquid.<br /><br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"Conditions concerning the surface of the sun many opinions are held. That it is hot beyond all estimate is indubitable. Whether solid or gaseous we are not sure. Opinions differ: some incline to the first theory, others to the second; some deem the sun composed of solid particles, floating in a gas so condensed by pressure and attraction as to shine like a solid."<br /><tt>-Recreations in Astronomy by Henry White Warren, D.D., 1879</tt></blockquote><br /><br />Ongoing study paid off near the end of the 19th century with this picture of the Sun:<br /><br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"The received opinion as to the constitution of the sun is that the <i>central mass</i>, or nucleus, is probably <i>gaseous</i>, under enormous pressure, and at an enormous temperature.<br /><br />The <i>photosphere</i> is probably a sheet of <i>luminous clouds</i>, constituted mechanically like the terrestrial clouds, that is, of small, solid, or liquid particles, very likely of carbon, floating in gas."<br /><tt>-Lessons in Astronomy, Charles A. Young, PhD., LL.D., 1896</tt></blockquote><br /><br />As to the source of its heat, there were several concepts advanced. One being that the Sun began as a white-hot mass. In the time since its creation, it had thrown off some heat to cool to its present temperature and color. As time passed, it would continue to throw off heat as it cooled. Under this model, it would have radiated more heat when it was hotter. As it cooled, it would emit more heat. This tied the geological record to the brief life of the Sun. Geological activity that appeared to take a very long time, with the present levels of heat received from the Sun, would actually have occurred at a far faster rate early in the history of the solar system. When the Sun and Earth were hotter, things moved faster. A geological formation that would have taken hundreds of millions of years to form at present rates might have actually been created in some small fraction of that time in a hotter, more energetic, time.<br /><br />Another idea about the Sun's heat was based on the new knowledge of meteors. The number of small masses in space was obviously numerous. They could count how many struck the atmosphere of the Earth. The Sun, as a far more massive object than the Earth, would clearly attract far more meteors. By counting the numbers of meteors falling to the Earth, 19th century scientists were able to calculate that the Earth was heated in some small degree by the infall of these meteors. Perhaps the Sun, with its much larger number of meteoric strikes, was heated enough to account for all the heat it produced? Then the heat of the Sun would last for as long as the meteoric material in the solar system.<br /><br />Combustion was also a possibility, particularly if the Sun were made of some unknown material that burns with especially high energy. The picture of the Sun's atmosphere as a sea of fire seemed to support this idea. Perhaps the energetic material of the Sun not only burned, but produced flammable gases when it burned, which would themselves burn at higher altitudes. To some, the corona that was visible around the Sun during eclipses appeared to be towering flames of hydrogen gas.<br /><br />Young states that some earlier ideas have been discarded:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"Maintenance of the Solar Heat.--We cannot here discuss the subject fully, but must content ourselves with saying first, <i>negatively</i>, that this maintenance cannot be accounted for on the supposition that the sun is a hot body, solid or liquid, simply cooling; nor by combustion; nor (adequately) by the fall of meteors on the sun's surface, though this cause undoubtably operates to a limited extent. Second, we can say <i>positively</i> that the solar radiation <i>can</i> be accounted for on the hypothesis first proposed by Helmholtz, that the sun is mainly gaseous, and shrinking slowly but continuously. While we cannot see any such shrinkage, because it is too slow, it is a matter of demonstration that if the sun's diameter should contract by about 300 feet a year, heat enough would be generated to keep up its radiation without any lowering of its temperature. If the shrinkage were more than about 300 feet, the sun would be hotter at the end of the year than it was at the beginning.<br /><br />We can only say that while no other theory meets the conditions of the problem, this appears to do so perfectly, and therefore has probability in its favor."<br /><tt>-Lessons in Astronomy, Charles A. Young, PhD., LL.D., 1896</tt></blockquote><br /><br /><b style="color:#ff7700;">The Collapsing Sun</b><br /><br />And so we have it. The only method that could account for the heat of the Sun. Other methods may contribute. These other factors, along with the exact make-up of the Sun's gases resulted in estimates for the Sun's shrinkage from about 140 feet per year to the about 300 quoted by Young. Lord Kelvin also considered this the most likely cause of the Sun's heat, and as new data became available he revised his estimates of the likely age and lifetime of the Sun. Each estimate came in shorter than the last. His estimates for the age of the Sun dropped from 40 to 100 million years down to 10-12 million years as more was learned.<br /><br />To common society, the expansion of the history of the universe from a few thousand years to several million was the opening of a vast, broad area of time almost unimaginable. Even the shortest of Lord Kelvin's estimates seemed more than vast enough. To the geologists, however, studying the processes of the formation of the Earth, the few million years that Lord Kelvin granted were not even close to enough to explain what they saw. But there was no disputing the science. The rate at which the Earth lost heat could be measured as well. Assuming that the Earth began as a molten mass, its own life could not have been more than a few million years to reach its current temperature.<br /><br />Yet the formations the geologists saw in the Earth appeared to take far longer to form. One response to the dilemma was a branch of Catastrophism. Not a Catastrophism married to an attempt to constrain all of time to the strictest views of Creationists, but a form of the theory that sought mechanisms to produce structures that would seem to take millions of years in far less time.<br /><br /><b style="color:#ff7700;">How Long Have We Got, Doctor?</b><br /><br />With the Sun collapsing into itself, and about ten million years behind it, how much longer can it last? What will the future bring?<br /><br />Returning to Doctor Young, we find:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"Age and Duration of the Sun.--Of course if this theory is correct, the sun's heat must ultimately come to an end; and looking backward it must have had a beginning. If the sun keeps up its present rate of radiation, it must, on this hypothesis, shrink to about half its diameter in some 5,000000 years at the longest. It will then be about eight times as dense as now, and can hardly continue to be mainly gaseous, so that the temperature must begin to fall quite sensibly. It is not, therefore, likely, in the opinion of Professor Newcomb, that the sun will continue to give heat sufficient to support the present conditions upon the earth for much more than 10,000000 years, if so long."</blockquote><br /><br />During this time between Herschel measuring the rate at which the Sun heated water in a tin cup and Doctor Young's writings, work had continued on nailing down just how much heat the Sun produced. This, and the larger picture of the Sun's operations and age was assessed in another book by Doctor Young, <b>The Sun</b>, published in 1897:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"We have spoken, a few pages back, of Professor Langley's experimental comparison between the brilliance of the solar surface and that of the metal in a Bessemer converter. At the same time he made measurements of the heat by means of a thermopile, and found the heat radiation of the solar surface to be <i>more than</i> eighty-seven times as intense as that from the surface of the molten metal...<br /><br />Thus, in the composition of a body's radiation, we get some clew to its temperature. Hitherto all such tests concur in putting the sun's temperature high above that of any known terrestrial flame.<br /><br />And now we come to questions like these: How is such a heat maintained? How long has it lasted already? How long will it continue? Are there any signs of either increase or dimunition?--questions to which, in the present state of science, only somewhat vague and unsatisfactory replies are possible.<br /><br />As to the progressive changes in the amount of solar heat it can be said, however, that there is no evidence of anything of the sort, however, that there is no evidence of anything of the sort since the beginning of authentic records. There have been no changes in the distribution of plants and animals in the last two thousand years, as must have occurred if there had been, within this period, any appreciable alteration in the heat received from the sun...<br /><br />What then, maintains the fire? It is quite certain, in the first place, that it is not a case of mere combustion. As has been said, only a few pages back, it has been shown that, even if the sun were made of solid coal, burning in pure oxygen, it could only last about six thousand years: it would have been nearly one third consumed since the beginning of the Christian era. Nor can its heat lie simply in the cooling of its incandescent mass. Huge as it is, its temperature must have fallen more than perceptably within an thousand years if this were the case.<br /><br />Many different theories have been proposed, two of which now chiefly occupy the field. One of the finds the chief source of the solar heat is in the impact of meteoric matter, the other is the slow contraction of the sun. As to the first, it is quite certain that a part of the solar heat is produced in this way; but the question is whether the supply of meteoric matter is sufficient to account for any great proportion of the whole. As to the second, on the other hand, there is no question as to the adequacy of the hypothesis to account for the whole supply of solar heat; but there is yet no direct evidence that the sun is really shrinking...<br /><br />We do not know enough about the amount of solid matter and liquid matter at present in the sun, or the nature of this matter, to calculate the future duration of the sun with great exactness, though an approximate estimate can be made...it is hardly likely that the sun can continue to give sufficient heat to support life on earth (such life as we now are acquainted with, at least) for ten million years from the present time.<br /><br />...we are inexorably shut up to the conclusion that the total life of the solar system, from its birth to its death, is included in some such space of time as thirty million years...<br /><br />At the same time, it is obviously impossible to assert that there has been no catastrophe in the past--no collision with some wandering star, endued, as Croll has supposed, like some of those we know of now in the heavens, with a velocity far surpassing that to be acquired by a fall even from infinity, producing a shock which might in a few hours, or a few moments even, restore the wasted energy of ages. Neither is is wholly safe to assume that there might not be ways, of which we yet have no conception, by which the energy apparently lost in space may be returned, at least in part, and so the evil day of the sun's extinction may be long postponed."</blockquote><br /><br /><b style="color:#ff7700;">A New Hope: Selective Sunlight</b><br /><br />But this does not close out other possibilities, newly proposed. All theories so far have presumed that sunlight is radiated in all directions of space around the Sun equally. But what if this isn't actually the case? What if the Sun only emits its energy in certain directions, one of which happens to be toward the Earth?<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"In 1882 Dr. C.W. Siemens, of London, proposed a new theory of the solar energy much in this line, and the scientific eminence of its author secured it most respectful consideration and discussion. Although it was soon abandoned as untenable...<br /><br />'The fundamental conditions' of Dr. Siemen's theory are the following, in his own words; <br />'1. That aqueous vapor and carbon compounds are present in stellar and interplanetary space.<br />'2. That these gaseous compounds are capable of being <i>dissociated</i> (decomposed into their elements) by radiant solar energy while in a state of extreme attenuation.<br />'3. That these dissociated vapors are capable of being compressed into the solar atmosphere by a process of interchange with an equal amount of reassociated vapors, the interchange being affected by the centrufugal action of the sun itself.'<br /><br />Moreover--and this is the point of the theory upon which he puts special emphasis--he teaches that these compound gases resulting from the combustion intercept the solar heat not received by the planets (heat which, from the human point of view, would otherwise be <i>wasted</i>), and utilize it in their own decomposition; thus the solar fire is made to prepare its own fuel from the ashes of its own furnace, and an explanation is found for its enduring constancy."<br /><tt>-The Sun, Dr. C. A. Young, 1897</tt></blockquote><br /><br />So we have one of several theories that somehow, the Sun's light does not spread equally through space. The light and heat that would be "wasted" on interstellar space is somehow preserved. Dr. Young rejects this specific theory, yet notes that there is nothing in it which is absurd. If the precepts that the theory are based on are correct (that space is filled with composite vapors, that light and heat can decompose them again into their elements) then the theory not only may be, but <i>must</i> be correct.<br /><br />In this case, the total amount of energy actually expended by the sun becomes far less, as only the light and heat reaching the planets themselves is lost. The problem is, that an interplanetary vapor would have an effect on the motions of the planets. An effect that should have been detectable even in Dr. Young's time. And that effect is not seen. A number of other difficulties arise as well. If some gas in the solar system absorbed the light that doesn't strike the planets, and assuming our solar system is no different from that of any other star, how is it that we're able to see those other stars? Why isn't their light either absorbed at the source, by their own local vapor, or absorbed upon reaching the vapors in our system?<br /><br />As Dr. Young states:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"And yet one almost regrets that the theory can not be accepted, for it would remove some very serious difficulties that now embarrass the problem of the evolution of our planetary system. The accepted contraction theory of Helmholtz certainly appears to allow too little time for the sun's lifetime of radiant activity to be consistent with a reasonable explanation of the process by which the present stat of things has come about."<br /><tt>-The Sun, Dr. C. A. Young, 1897</tt></blockquote><br /><br /><b style="color:#ff7700;">The Turn of the Century</b><br /><br />So we have an inadequate theory, but one which is fully supported by science, unlike any other.<br /><br />In the last year of the 19th century, Dr. Simon Newcomb sums up the situation like this:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"The view now commonly held is that the heat of the sun is kept up by the constant contraction of its mass through the gravitation of its particles toward the center. The theory of energy teaches us that heat is produced when a body falls toward a center without having its velocity increased. For example, the temperature of the water of Niagra Falls must be about one-quarter of a degree higher after it strikes the bottom than it is before it goes over the falls...<br /><br />If this view is correct, a time must come when the sun can contract no more. Then a solid crust will form over its surface, this crust will gradually grow dark and cold. But the period necessary for this is many millions of years, so we need not trouble ourselves about it."<br /><tt>-Elements of Astronomy, Dr. Simon Newcomb, 1900</tt></blockquote><br /><br />The Dying Sun<br /><br />Or is Dr. Newcomb merely whistling in the dark? The study of the Sun with instruments such as bolometers and spectroheliographs has only just started at the time of his writing. By 1923, a more complete picture of the surface of the Sun, including not only the visible but the invisible, had emerged.<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"It is a portentious vitality for our sinking sun. And that our sun has passed the prime of its life follows from all that we have said. It contains some forty of our chemical elements. A star in the prime of life has very few of them, and it has hardly any absorbing layer of cooler vapors. The face of our sun is covered with a veil of such vapors. The spots are mighty oceans of them. The vitality of the sun has sunk to such a point that it cannot entirely keep itself ablaze. The dark vapors will gradually increase. Our yellow star will become a red star. The chemical combinations in the spots will increase until large areas shine with a dull red glow. It will be too cold for life on the planets. When? Not for many millions of years--the general tendency now is to say, not for tens or hundreds of millions of years. But here we are on less firm ground, and we must wait until we know more about the evolution of stars."<br /><tt>-The Wonders of the Stars, Joseph McCabe, 1923</tt></blockquote><br /><br />Something else new has appeared by this time as well. In the same book where the Sun is described as a dying star, we find the following about its sources of energy:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"There is no question of combustion of the stars, as in our fires. It would be impossible to sustain the fires of the stars for hundreds (perhaps thousands) of millions of years, as they are sustained, by combustion. The gradual contraction of the mass of the sun is one great source of heat. Some astronomers think it is an all-sufficient source, but the general belief now is that the heat given off as the lighter atoms combine to form the heavier is a most important source of the sun's heat."<br /><tt>-The Wonders of the Stars, Joseph McCabe, 1923</tt></blockquote><br /><br />And here we have it. A new source of energy, one that was previously unknown to Lord Kelvin in his calculations. The "heat given off as the lighter atoms combine to form the heavier" is what we call fusion power today. Note, also, what the above account gives for the lifetime of a star. No longer ten or possibly tens of millions of years, but now hundreds or perhaps thousands of millions of years--billions to us today. Though Joseph McCabe sees the sun as a dying ember, the science of his time allows for a Sun that has seen a life of perhaps billions of years. Long enough for the Earth to form as the geologists see it, without any special trickery to get here.<br /><br /><b style="color:#ff7700;">New Life</b><br /><br />By 1932 the picture of what powers the Sun has become pretty well complete. In Simon Newcomb's Astronomy for Everybody, revised by Robert H. Baker, PhD., the section on "The Source of the Sun's Heat" reviews the ideas of the last century. It states the well-characterized quantity of energy that the Sun emits, given as 70,000 horsepower per square yard of surface area. The concept of the Sun as a cooling body is discarded, as is the concept of the Sun as a combustable mass. The infall of meteors is recognized as an ancillary source of energy, but as far too small to account for the amount of energy radiated by the Sun.<br /><br />Then comes the contraction theory. The strong scientific basis for it is described, as well as its agreement with other current scientific theories. The discussion concludes:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"The contraction theory pictured a gloomy prospect, the end of the world of living beings within a brief interval--brief astronomically, at least. But in recent years, the contraction theory has met with disapproval, along with the hypothesis of Laplace. In shrinking to its present size from dimensions as large as we please, the sun has gained enough heat to keep it shining at the present rate for scarcely twenty million years. It has certainly been shining at this rate for a vastly longer time. Thus the contraction theory fails to account for the maintenance of the sun's radiation in the past. We have no greater confidence in its prediction for the future. There is, in fact, no certain evidence that the sun is contracting progressively at all."<br /><tt>Simon Newcomb's Astronomy for Everybody, rev. by Robert H. Baker, PhD., 1932</tt></blockquote><br /><br />And so, the "collapsing Sun" has been laid aside. An entirely new, almost magical source of energy unknown to scientists of the 18th century has appeared. Atomic energy:<br /><br /><blockquote style="line-height:1.5; padding: 20px 20px; background-color:#333333; color:#ffcc00; font-family:serif; font-size:100%;">"With the discovery of radioactivity, astronomers inquired as to whether the sun's long-continued radiation might not be kept up by the disintegration of radium and similar elements in the interior. Appropriate calculations soon gave the negative answer. A way is left open, however, if we wish to imagine that the sun contains radioactive elements more complex than the heaviest element, uranium, found on the earth. It should be added that we have no knowledge of such super-radioactive elements."</blockquote><br /><br />But wait! What? Radioactivity doesn't explain the sun? Such radioactivity had explained the heat loss of the Earth. The Earth was now known to not be a cold mass after its long life because most of its heat comes not from being a cooling mass but from the heating caused by radioactive elements within it.<br /><br />In fact, McCabe's answer from 1923 was the correct one, which was missed somehow in Baker's revision of Simon Newcomb's landmark book. The combination of elements into higher elements, or atomic fusion, turned out to be the primary source of power within our Sun. The fusion occurs deep within the Sun, in an area around the deepest core of the Sun. The heat slowly filters out through the various layers of the Sun. This heat "puffs up" the Sun, preventing its contraction. In time, the Sun will burn through its present fuel of hydrogen, and will change to a reaction fusing helium. This will cause the Sun to heat up even more, and its outer atmosphere will puff up even more to create a "red giant" with a greater surface area to radiate the heat.<br /><br />As a red giant, the Sun will expand beyond the Earth's orbit, placing the Earth within the outer reaches of the Sun's atmosphere and destroying it. But rather than a few million or tens of millions of years, our planet has a future of about five billion years before this occurs.<br /><br />One hundred years ago, people looked up and saw our Sun as a dying star, collapsing in upon itself. The past was limited to a few million years, and the future as well. Their sky was ruled by a shuddering, poxed old star in its dotage.<br /><br />But already, at that time, the discoveries were underway to change that view. An entirely new source of energy was found, as investigations were made into why the accepted view of the Sun did not entirely account for the details of what was known. These investigations gave us a whole new branch of physics, and a whole new span of time in which to exist.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0tag:blogger.com,1999:blog-5645593341528211288.post-83059213111035784142010-08-14T14:54:00.000-07:002010-08-14T20:07:35.780-07:00What is a Galaxy, Anyway?Though we can't see it directly, the sky is full of galaxies. A few can be seen directly, like the Andromeda Galaxy, and some others under excellent viewing conditions. A pair of binoculars will show more of them, and in fact is one of the best ways of viewing Andromeda. Andromeda covers such a large area of sky that few telescopes will show all of it at once--it takes the wide field of view of a pair of binoculars to see it all.<br /><br />In pictures taken by space telescopes, we can see fields filled with galaxies. The galaxies are scattered across the image like stars. These images cover a ridiculously small area of the total sky above us. If the number of galaxies in these pictures is multiplied by the number of pictures that it would take to cover the entire sky, we learn that there are more galaxies in the sky than there are stars that we can see with our eyes, even on the darkest of nights.<br /><br />Our view of a galaxy has not always been the view we have now, though. The word "galaxy" has had, historically, a rather slippery sense of meaning.<br /><br /><b style="color:#0077ee;">The Galaxy as a Place of Myth and Legend</b><br /><br />Before the telescope was turned on the heavens by Galileo in 1609, there was only one Galaxy. The Galaxy. Galaxy referred to the Milky Way. Known for as long as anyone has looked upward, it's a part of the sky that appears to be a stream of milky light. Exactly what it was couldn't be known, of course. Myths gave it various forms, such as milk from a great godlike cow, or a path of the gods.<br /><br />Galaxy comes from the Greek galax, the word for milky. Galaxy is a combining form. To our ears, it falsely suggests the sound of lacto, or the Latin for milk, but it's actually unrelated. To the Romans, the Milky Way was Via Lactea. Milky Way is a literal translation of that.<br /><br />When Galileo turned his telescope on it, he was the first to see it as stars rather than as a milky cloudiness. The stars in it are so close together and so numerous that there's no way our eyes can make it out as stars without the resolving power of the telescope. The telescope not only magnifies the view, but improves the contrast we see, making it easier to see the individual stars by magnifying the spaces between them and allowing us to pick them out from the general glare.<br /><br /><b style="color:#0077ee;">The Galaxy as Nothing Special</b><br /><br />From that time on, the Milky Way, or the Galaxy, became a name for an area of the sky with most of the stars in it. In the book <u>Elements of Astronomy</u> by Simon Newcomb, published in 1900, the terms "galaxy" and "Milky Way" do not even appear in the index. The Milky Way receives only one short mention in the book, describing Galileo's discovery. The 1886 book <u>Recreations in Astronomy</u> by H.W. Warren has "Milky Way" in the index with two citations, but "galaxy is absent. The greater of the two passages cited reads:<br /><blockquote style="color:#ff0000;">Every one has noticed the Milky Way. It seems like two irregular streams of compacted stars. It is not supposed they are necessarily nearer together than the stars in the sparse regions about the pole. But the 18,000,000 stars belonging to our system are arranged within a space represented by a flattened disk. If one hundred lights, three inches apart, are arranged on a hoop ten feet in diameter, they would be in a circle. Add a thousand or two more the same distance apart, filling up the centre, and extending a few inches on each side of the inner plane of the hoop: an eye in the centre, looking out toward the edge, would see a milky way of lights; looking out toward the sides or poles, would see comparatively few. It would seem as if this oblate spheroidal arrangement was the result of a revolution of all the suns composing the system.</blockquote><br /><u>Lessons in Astronomy</u> by Chales A. Young, from 1896, contains one entry in the index under "Milky Way, the", and one under "Galaxy, the", both giving the same citation. The description given is as follows:<br /><blockquote style="color:#ff0000;">The Galaxy, or Milky Way.--This is a luminous belt of irregular width and outline, which surrounds the heavens nearly in a great circle. It is very different in brightness in different parts, and is marked here and there by dark bars and patches, which at night look like overlying clouds. For about a third of its length (between Cygnus and Scorpio) it is divided into two roughly parallel streams. The telescope shows it to be made up almost entirely of small stars from the eighth magnitude down; it contains, also, numerous star clusters, but very few true nebulae.<br /><br />The galaxy intersects the ecliptic at two opposite points not far from the solstices, at an angle of nearly 60 degrees, the north of the "galactic pole" being, according to Herschel, in the constellation of Coma Berenices. As Herschel remarks,--<blockquote style="color:#ff7700;">"The 'galactic plane' is to the sidereal universe much what the plane of the ecliptic is to the solar system,--a plane of ultimate reference, and the ground plane of the stellar system."</blockquote></blockquote><br /><br />It further describes the distribution of the stars in the heavens as being non-uniform, but that with what is known can give some information about the structure of the Stellar Universe:<br /><blockquote style="color:#ff0000;">The great majority of the stars we see are included within a space having, roughly, the form of a rather thin, flat disc, like a watch, with a diameter eight or ten times as great as its thickness, our sun being not very far from its centre...As to the Milky Way itself, it is not certain whether the stars which compose it form a sort of thin, flat, continuous <i>sheet</i>, or whether they are arranged in a sort of <i>ring</i> with a comparitively empty space in the middle, where the sun is situated, not far from its centre.</blockquote><br /><br />Following this comes a section asking whether the stars form any sort of system, mentioning that it is unlnown whether gravitation operates between the stars and whether there might be some sort of orbital motion that defines the overall form of the Stellar Universe, with a concept called <i>Maedler's Hypothesis</i> being somewhat more likely, that there is motion about a common center of gravity. It goes further in naming Alcyone, in the Pleiades, as a star described as closest to that center and therefore the possible "central sun", but discards the idea as having no proof to sustain it.<br /><br />Over all, the subject is treated lightly, though in great thoroughness for the books of the time. After two pages on the Stellar Universe, the book returns to the <i>serious</i> discussion of the solar system.<br /><br /><b style="color:#0077ee;">The Revolution</b><br /><br />In these same books, in sections which are practically appendices to the important main matter of the nature and operation of stars and the solar system, there are brief mentions of nebulae, "clouds" in space. Among these are some unusual ones taking the form of spirals. The spirals go unmentioned in Newcomb's book. In Warren's book, they are only listed as one of many possible shapes of nebula:<br /><blockquote style="color:#ff0000;">"Nebulae are of all conceivable shapes--circular, annular, oval, lenticular, conical, spiral, snake-like, looped, and nameless."</blockquote><br />Young's book takes advantage of the very latest work in photography and spectroscopy. It has a more extensive section on nebulas, stating that photography reveals features which, for example, reveal a regular annular structure in the Andromeda nebula. Conclusions formed by the new information are absent, however. There is only the excitement that comes with new information to be studied.<br /><br />The 1923 book <u>The Wonders of the Stars</u> by Joseph McCabe is an exuberant popular book on astronomy that leaps into the subject of the spiral nebulas, however:<br /><blockquote style="color:#ff0000;">Some astronomers think that spiral nebulae may be stages in the formation of solar systems like ours. It is estimated that if two stars approached within a few million miles of each other they would raise such tides (analogous to the ocean-tides raised on the earth by the moon) of metal that a vast quantity would be shot out into space. We are imagining, remember, a volcanic outpour streaming <i>thousands of millions</i> of miles into space. If two such mighty streams were shot out opposite sides of a star, its gravitational power would cause them to wind round the central mass, and it is said the resulting structure would be like the spiral nebula in the photograph. The arms and the star would continue to whirl around, like a gigantic Catherine-wheel. The next stage would be that the matter contained in the spiral arms would begin to gather round the denser centres, and ultimately it would be all (except, perhaps, for a little residual matter, to make meteors) collected in a large number of smaller globes circulating around the star.</blockquote><br /><br />Even at this stage, however, questions appear. The rotation of the spiral nebulas has been observed, and questions about their size and distance from these measurements can not be answered, but at the very least some boundaries can be established. As mentioned in the McCabe book, what is known about the spirals would seem to make them too large for solar systems, as they were then understood.<br /><br /><b style="color:#0077ee;">The Island Universes</b><br /><br />About the time of McCabe's book, astronomers were beginning to establish distances to these spiral nebulas. In Young's book, it was an open question whether they were part of the same system as the stars around us. In McCabe's book, he notes that some feel they are outside the system of stars but discounts the idea himself.<br /><br />The controversy about the size of the Milky Way and its relationship to the spiral and other nebulas which appeared to be at exteme distances was known as "<a href="http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate20.html">The Great Debate</a>".<br /><br />This work found that the distances to the spiral nebulas, and many others that were not of spiral form, were greater than those to any of the stars known in our "Stellar Universe." This placed them <i>outside</i> that universe and made them ambiguous objects, compared to those nebulas that had been established as being within the Stellar Universe.<br /><br />The name "Island Universe" arose for these objects, though it was an abuse of the term "universe." They appeared to be islands of stars and nebulas that fell outside the main system of which we are part. The falsehood of our own system being the primary among them fell away quickly as measurements revealed the sizes of these "islands." Their extent was as great as that as the circle of stars about us in the Milky Way.<br /><br />In 1932 Robert H. Baker revised the popular book <u>Astronomy for Everybody</u> written in 1902 by Simon Newcomb. He updated it with the vast quantity of new understanding that had arisen. It includes a new chapter titled "Galaxies."<br /><blockquote style="color:#ff0000;">In the description of the Milky Way we have noticed some of the star clouds, in particular, the great Sagittarius cloud whose center is 50,000 light-years away, and the somewhat smaller and nearer Scutum cloud. According to the view recently set forth by Shapley, these and other star clouds are <i>galaxies</i>, that is to say, vast assemblages of stars and nebulae. They average 10,000 light-years in diameter. Some are considerably smaller, while the largest are three or four times greater in diameter.<br /><br />The galaxy of which our sun is a member is known as the <i>local system</i>...These star clouds are grouped nearly in one plane in the supergalaxy which we call the galactic system. For the past century and a half, astronomers have been trying to determine precisely the form and extent of this system whose principal feature, as we see it in projection in our skies, is the Milky Way.</blockquote><br /><br />At this point there was still uncertainty about where to draw the lines. Were the various star clouds that we now call the Milky Way Galaxy all part of one galaxy, or several galaxies in an interacting system? Were the external galaxies part of this system, or were they entirely independent?<br /><br />Over time the consensus became that the external nebulas, the Island Universes, were full independent galaxies in their own right, and that the various star clouds around us in the near distance were different components of a single spiral structure like that seen in Andromeda and Triangulum.<br /><br />The word galaxy became a general term for the "Island Universes" or assemblages of star clusters independent of our own. In spite of the fact that the word itself means "Milky Way", it was extended to include those structures in space like our own Milky Way, as well as describing the Milky Way itself.<br /><br /><b style="color:#0077ee;">The Spiral Path</b><br /><br />The galaxy began as a thing in the sky. Unique, mysterious, and unexplained. It was an object of legend, where gods tread, that led from one storied place to another, with a story behind its unique existence. Then, with the telescope, it was seen to be nothing more than an aggregate of common objects. No longer was it a mystery. It was just a bunch of stars. Like pebbles in the aggregate of a path, their number was nothing of greatness, just a result of their proximity.<br /><br />Then, with a closer look at the star clouds within the Milky Way, and anomalous objects outside it, it was found to be one of a number of immense associations of stars in our universe. As we dream of and seek other civilizations like our own, the galaxy, as its own mini-universe, has become a place of legend again. Where so many stars come together, we infer many planets. Where so many planets lie, there lie the greatest chances for other life like our own. New places for others with consciousness to arise and to experience their own epic sagas.<br /><br />Once again, "galaxy" has become a place of myth and legend. In 1977 we were treated to the line "A long time ago, in a galaxy far, far away..." Since then, the land of galaxies has only extended further and become more mysterious and colorful, thanks to the amazing images provided by our astronomers.<br /><br />'Galaxy' has gone from naming a thing, to an area, to a span of stars that fills a small universe (by present standards) to a thing that is scattered in unimaginable plurality through a far, far larger universe. A universe that is once again large enough for stories of strange peoples and strange things that reflect our view of the vast unknown.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com1tag:blogger.com,1999:blog-5645593341528211288.post-34768262921561567112010-08-10T14:56:00.000-07:002010-08-10T15:02:50.036-07:00Which Star is That? Don't Fret!In the evening I really enjoy watching the stars appear. It's sort of a personal challenge with me, which I find relaxing (believe it or not.) I like to see how early I can pick out a star. Even better, I like to know what star it is.<br />
<br />
It's hard to tell, if you don't already know the star from a prior evening's viewing. I recognize stars by their relationships to each other, and if it's the first star I see, there aren't any other stars. That leaves me with guessing on the basis of how high it is in the sky, the time of year, and so on.<br />
<br />
Stars change their positions in the sky, which is why I use the relationships between them to identify them. Tonight Vega will appear up there, in a month's time it'll be over <i>there</i>. If I don't get a chance to look at it in between, I might think I'm seeing Arcturus when it first appears.<br />
<br />
Location Matters<br />
<br />
On top of that, when I leave my most frequented observing locations, the sky appears to change. The parts of the sky I can see, and the parts that are blocked by local scenery change. I might not know which way is north as well, or as accurately. This happens most often when I'm at public star parties in new locations. There I am, supposedly one of the expert astronomers. Someone walks up to me as the first stars are appearing and I'm still trying to get my bearings.<br />
<br />
"What star is <i>that</i>?" they'll ask.<br />
<br />
And I won't know. One of the very brightest stars in the sky, and I can't tell which it is.<br />
<br />
What kind of an astronomer am I anyway?<br />
<br />
<div style="color: #f1c232;"><b>Get It Wrong</b></div><br />
Fortunately I can usually make a guess. And I'm honest about it. I'll say, "I don't know, but from where it is and how bright it is I <i>think</i> it's..." whichever. I guess, and then in the next half hour I'll find out if I'm right or wrong.<br />
<br />
When I'm by myself, I guess, too. I try to figure out what star I'm seeing. I try to put together a few facts, then make a guess and check back on myself later when I can see the star's neighbors. The only way for me to get better is to be willing to get it wrong, and make a guess. Later, when I find out whether I was right or wrong I can re-assess the reasons I used for guessing as I did. Then I learn something.<br />
<br />
Like, yes, Arcturus really can appear that low in the sky, during this time of year. Or, yes, we're far enough along in the year for Altair to start to show. Sometimes it sticks, sometimes it doesn't. But over time, it adds up and I get better at it.<br />
<br />
<div style="color: #f1c232;"><b>Start at Dark</b></div><br />
At the outset, I had to learn the stars when I could see them among the other stars. I didn't learn the Winter Triangle and Summer Triangle at twilight, I learned them when it was fully dark. I also had to learn to remember which was which, and which constellation went with each. The same goes for the other bright stars.<br />
<br />
As I often tell people when they're impressed by what I know, I wasn't born knowing this stuff. I had to learn it piece by piece, just like anyone else. The first pieces were the basics. The next step was challenging myself to do more. Like pick out the first stars and know what they are--maybe.<br />
<br />
The next step in expanding on the ability to tell one star from another comes with trying to pick out the stars earlier when you're already familiar with the sky. You've been out under the dark sky within the past few days. You pretty well remember what you saw in the early part of the night. Now you see what you can see earlier. The stars will be in slightly different positions, shifted to the east from where you remember them being. But not due east, since the stars travel in circles about the pole.<br />
<br />
Then as you see stars, guess to yourself. "I think that's Spica, because that other star over it is probably Arcturus." Then check up on yourself later, when more stars are out.<br />
<div style="color: #f1c232;"><b><br />
</b></div><div style="color: #f1c232;"><b>Optical Illusions</b></div><br />
As it is, I now press myself to try to find stars when the sky is still bright. When doing this, I remind myself that the definition of "detectable" is that you can find it 50% of the time. And that's about how it works out. I'll scan the sky, and it's hard not to have my eyes either glaze over or focus on some near object while looking at the apparently empty sky. Then I'll see a little pinprick of light standing out, barely. Aha! A star!<br />
<br />
Then I'll move my head. And it'll disappear. It can take me several minutes of looking to find it again. If I've got a scope, I'll try to keep it in view by staring at it as I bend toward the viewfinder. And it'll disappear as I start to crouch. It's funny, but it often seems it's harder to see things that are just detectable if my eyes aren't level with each other.<br />
<br />
But sometimes, I can manage it. What helps the most in re-finding a star at this stage is locating the star with respect to something on the horizon. It's one hand span above that tree top. If I put my hand just like so it'll be just over the tip of my pinky. And so on.<br />
<br />
It really does feel like an optical illusion. You can practically feel it slipping in and out of view sometimes. It's like one of those pictures where you have to really concentrate to see the picture hidden within the picture.<br />
<br />
I know it doesn't <i>sound</i> relaxing. Bit it is, if you don't get wound up over it and just sort of let it happen. After all, in a few minutes the sky will be a little darker. So things will be a little easier to see. Can't catch it now? Wait a few minutes. Check some other part of the sky in the meanwhile. Carry on a conversation while you scan.<br />
<br />
Most of all, don't be afraid of being wrong. Make guesses. As they say, you miss every shot you don't take. Take a shot, and see what happens. If nothing else, you'll have to dredge up some star names from memory, even if you aren't sure which stars they apply to, yet.<br />
<br />
<div style="color: #f1c232;"><b>Relax to See More</b></div><br />
The most important reason to stay relaxed? Your eyes are far more sensitive to small differences in contrast when you're relaxed. If you take it easy, and enjoy the view, you'll see more.saundbyhttp://www.blogger.com/profile/05472603072142005189noreply@blogger.com0