Astro Basics

Observing Mars

2012-01-24T14:47:00.000-08:00

Mars 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.

Image by Arnomane

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 about 13.9 arcseconds across, 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.

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 as large as the Moon! This is known as the Mars Hoax, 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!

Make It Bigger

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.

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.

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.

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 very well made refractors 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.

Now in Living Color!

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.

I observe Mars with all the different colors of filter, but I find the red and green color filters to bring out the most unique detail. A blue filter is often worth observing with, but at other times it doesn't do much but darken Mars. Yellow and orange filters bring out details, sometimes better than a red filter, at other times worse. 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.

Take a Picture, It'll Last Longer

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.

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.

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.

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.

At which point it's time to start another drawing. :)

Cold Weather Astronomy: Be Prepared!

2012-01-14T07:30:00.000-08:00

In my prior article 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.

Fashion Sense and Sensibility

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.

Humidity Good and Bad

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.

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.

The Layered Look

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.

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.

The outer layer should prevent wind from getting in and your body's heat and moisture from getting out.

Easily Freezable Bits
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.

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.

For example, I usually wear the following on my feet:

Inner cotton socks

Acrylic knee-high socks

Aluminized socks

Outer wool or thick cotton socks

I have a loose pair of older leather boots that I wear in winter to accommodate these layers of socks.

On my head I wear a balaclava under a heavy winter hat.

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.

Internal Preparation

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.

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.

Breaks and Self-Inspections
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.

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.

Two Ways to Err
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.

Don't miss out on winter observing, and don't over-do it, either!

Plus, if you have any personal tips or tricks you use, please share them in the comments.

Keeping Warm When Observing in Winter

2012-01-07T11:04:00.000-08:00

Winter skies 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.

Losing Sky to Gain Warmth
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.

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.

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.

Cover the Cold Ground
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.

Wind
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.

Slippery Slopes
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.

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 got 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.

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.

Warm Up Shack
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.

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!)

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.

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.

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!)

Prepare Yourself

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.

Winter Observing

2012-01-01T12:18:00.000-08:00

This 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.

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.

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.

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.

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.

Stay warm with layered clothing, good socks, and good gloves.

Observing the Earth

2011-11-11T06:04:00.000-08:00

One of the easiest planets to observe is our own, the Earth.

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.

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.

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 sure there must be a shower, there were so many meteors, when there was none.

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.

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!

The Phases of Venus

2011-10-30T05:41:00.000-07:00

Venus 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.

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!"

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 without 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 away from the Sun. Practice sweeping in the correct direction before your eyeball is at the scope.

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.

Venus shows a full set of phases, from new and thin crescent phases to a Full Venus.

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.

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.

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.

Viewing Planet Mercury

2011-10-23T05:29:00.000-07:00

Planet 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.

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.

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.

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.

Learning the Constellations

2011-08-05T12:24:00.000-07:00

Learning 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.

One Step At a Time

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.

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.

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.

Season's Greetings
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.

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.

High and Low
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.

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.

Wine Tasting Under the Stars

2011-07-12T16:55:00.000-07:00

If 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.

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 David Girard Vineyards, in Coloma, California.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Double Stars

2011-06-14T09:25:00.000-07:00

About 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.

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.

Albireo

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.

Albireo, image by Hewholooks

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.

Cor Caroli

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.

Cor Caroli

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.

Algeiba

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.

Algieba, image by Roberto Mura

Binoculars will reveal the double, but I prefer to view it at low powers in a telescope.

Omega Scorpii

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.

Omega 1 and Omega 2 Scorpii, image by Roberto Mura

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.

Rainy Nights

2011-03-20T21:58:00.000-07:00

When the weather doesn't allow observation, what do you do?

1. Tune Up the Telescope.

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.

2. Go Over the Observation Logs.

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.

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.

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.

3. Prepare for Future Observations

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.

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.

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.

4. Build a New Accessory

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.

5. Take Up Radio Astronomy

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 something 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.

I made a simple corner reflector antenna. 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.)

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 see Jupiter).

Since then I have set up radio receivers to hear meteors and receive amateur radio "moonbounce" communications. All pretty easy stuff.

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. :)

Is It a Planet, or Not?

2010-09-21T12:37:00.000-07:00

Just as the word "galaxy" has changed its meaning through time, the word "planet" has changed from meaning one thing to another.

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.

The Original Planets

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.

Because they wandered, they got the name "planetes" from the Green word for "wanderer" (root plan-). So a "planet" was something that was seen to wander across the sky. The planets were:

The Sun

The Moon

Jupiter

Venus

Saturn

Mars

Mercury

Notice that the Earth was not a planet. What a laughable idea! The Earth's not in the sky. But notice that the Sun is a planet. Of course, it is in the sky, and it moves independently of the stars.

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.

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.

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.

The Sun-Centered Universe

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."

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.

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."

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.

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."

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.

Planetary Orbits from Recreations in Astronomy, 1886

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.

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.

Are Asteroids Planets?

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.

In the 1869 tenth edition of Outlines of Astronomy 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:

"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."
-Sir John Herschel, 1869

He defines them as planets thus:

"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 planets. [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."
-Sir John Herschel, 1869

Recreations in Astronomy, 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:

"...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."
-Rev. H.W. Warren, 1886

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.

In Dr. Charles Young's Lessons in Astronomy 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.

The Sun, as Seen from Planets Flora and Mnemosyne

In Dr. Simon Newcomb's Elements of Astronomy 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.

Fellow of the Royal Society Richard A. Procter ignores the existence of the minor planets entirely in his 1901 book Other Worlds Than Ours. 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.

In 1923 Joseph McCabe refers briefly to the asteroids, not as planets, but as "planetoids." In The Wonders of the Stars 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.

Other Planets?

Aside from the asteroids, it was thought that as many as four planets had been seen inside the orbit of Mercury. Lessons in Astronomy includes a brief section on Intra-Mercurial Planets, whereas Recreations in Astronomy goes a bit further by having a chapter on planet Vulcan.

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.

Pluto

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.

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.

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.

New Qualifications for Planets

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.

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.

Xena/Eris

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.

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.

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.

The Third Step

The first two requirements for the new definition of "planet" were uncontroversial. They are:

The object must be in orbit around the sun.

The object must be massive enough to pull itself into a spherical shape.

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."

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.

But under the process the IAU followed, a third rule was added:

The object must have cleared the area around its orbit.

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.

Is This the Right Committee?

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.

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.

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.

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.

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.

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.

Adding to the Controversy

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."

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.

By that light, we presently have 12 known planets in the solar system. In order from the Sun by average distance they are:

Mercury

Venus

Earth

Mars

Ceres

Jupiter

Saturn

Uranus

Neptune

Pluto

Haumea

Makemake

Eris

Emotional Content

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."

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.

Slice and Dice

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.

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.

Other Words, Other Worlds

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.

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.

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.

De-define Planet?

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?

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.

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.

New Data Changes Old Words, Again

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.

Chances are we're going to be using the word "planet" in a new way very soon.

The Collapsing Sun

2010-08-30T14:38:00.000-07:00

"Let my eyes look upon the Sun
Until I have been filled with light!
Darkness leaves when there is sufficient light.
May I who am truly dead still behold
the brilliance of the Sun!"
-Gilgamesh, The Epic of Gilgamesh, Tablet X

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.

A Problem of Timing

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?

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.

What Heats the Sun?

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.

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.

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?

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:

"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.
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."
-Wells's Natural History, David A. Wells, 1861

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.

"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."
-Recreations in Astronomy by Henry White Warren, D.D., 1879

Ongoing study paid off near the end of the 19th century with this picture of the Sun:

"The received opinion as to the constitution of the sun is that the central mass, or nucleus, is probably gaseous, under enormous pressure, and at an enormous temperature.

The photosphere is probably a sheet of luminous clouds, constituted mechanically like the terrestrial clouds, that is, of small, solid, or liquid particles, very likely of carbon, floating in gas."
-Lessons in Astronomy, Charles A. Young, PhD., LL.D., 1896

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.

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.

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.

Young states that some earlier ideas have been discarded:

"Maintenance of the Solar Heat.--We cannot here discuss the subject fully, but must content ourselves with saying first, negatively, 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 positively that the solar radiation can 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.

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."
-Lessons in Astronomy, Charles A. Young, PhD., LL.D., 1896

The Collapsing Sun

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.

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.

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.

How Long Have We Got, Doctor?

With the Sun collapsing into itself, and about ten million years behind it, how much longer can it last? What will the future bring?

Returning to Doctor Young, we find:

"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."

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, The Sun, published in 1897:

"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 more than eighty-seven times as intense as that from the surface of the molten metal...

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.

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.

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...

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.

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...

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.

...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...

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."

A New Hope: Selective Sunlight

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?

"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...

'The fundamental conditions' of Dr. Siemen's theory are the following, in his own words;
'1. That aqueous vapor and carbon compounds are present in stellar and interplanetary space.
'2. That these gaseous compounds are capable of being dissociated (decomposed into their elements) by radiant solar energy while in a state of extreme attenuation.
'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.'

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 wasted), 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."
-The Sun, Dr. C. A. Young, 1897

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 must be correct.

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?

As Dr. Young states:

"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."
-The Sun, Dr. C. A. Young, 1897

The Turn of the Century

So we have an inadequate theory, but one which is fully supported by science, unlike any other.

In the last year of the 19th century, Dr. Simon Newcomb sums up the situation like this:

"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...

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."
-Elements of Astronomy, Dr. Simon Newcomb, 1900

The Dying Sun

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.

"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."
-The Wonders of the Stars, Joseph McCabe, 1923

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:

"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."
-The Wonders of the Stars, Joseph McCabe, 1923

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.

New Life

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.

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:

"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."
Simon Newcomb's Astronomy for Everybody, rev. by Robert H. Baker, PhD., 1932

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:

"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."

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.

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.

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.

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.

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.

What is a Galaxy, Anyway?

2010-08-14T14:54:00.000-07:00

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.

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.

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.

The Galaxy as a Place of Myth and Legend

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.

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.

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.

The Galaxy as Nothing Special

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 Elements of Astronomy 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 Recreations in Astronomy 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:

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.

Lessons in Astronomy 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:

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.

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,--
"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."

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:

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 sheet, or whether they are arranged in a sort of ring with a comparitively empty space in the middle, where the sun is situated, not far from its centre.

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 Maedler's Hypothesis 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.

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 serious discussion of the solar system.

The Revolution

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:

"Nebulae are of all conceivable shapes--circular, annular, oval, lenticular, conical, spiral, snake-like, looped, and nameless."

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.

The 1923 book The Wonders of the Stars by Joseph McCabe is an exuberant popular book on astronomy that leaps into the subject of the spiral nebulas, however:

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 thousands of millions 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.

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.

The Island Universes

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.

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 "The Great Debate".

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 outside that universe and made them ambiguous objects, compared to those nebulas that had been established as being within the Stellar Universe.

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.

In 1932 Robert H. Baker revised the popular book Astronomy for Everybody 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."

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 galaxies, 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.

The galaxy of which our sun is a member is known as the local system...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.

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?

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.

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.

The Spiral Path

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.

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.

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.

'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.

Which Star is That? Don't Fret!

2010-08-10T14:56:00.000-07:00

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.

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.

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 there. If I don't get a chance to look at it in between, I might think I'm seeing Arcturus when it first appears.

Location Matters

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.

"What star is that?" they'll ask.

And I won't know. One of the very brightest stars in the sky, and I can't tell which it is.

What kind of an astronomer am I anyway?

Get It Wrong

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 think it's..." whichever. I guess, and then in the next half hour I'll find out if I'm right or wrong.

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.

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.

Start at Dark

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.

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.

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.

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.

Optical Illusions

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!

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.

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.

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.

I know it doesn't sound 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.

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.

Relax to See More

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.

StellarVue Dark Sky Star Party

2010-06-16T16:13:00.000-07:00

There are two kinds of star parties. There are the "public" parties, where amateur astronomers show the sky to non-astronomers. I participate in about 20 of these each year, and I also hold my own impromptu events where I pull my scope out at some place I happen to be when it's dark and show the sky to anyone who's nearby and not too nervous to look.

The other kind of star party is the sort where amateur astronomers gather to observe in especially good conditions. Usually this means dark skies, a site that's kept free of lights that affect observation, and the attendees are amateur astronomers of all skill levels, from beginner to expert, with few people who aren't observers of one sort or another.

One of these "astronomers only" star parties is the StellarVue Dark Sky Star Party. It is held annually by the owner of StellarVue, Vic Maris. For the past two years it has been held at an RV park in the tiny little town of Likely, CA, in northeast California. The whole area it is in has very little population, meaning no light pollution. It's also at a moderately high altitude, about 5400 feet.

StellarVue's Picture Gallery for the 2010 DSSP.
I was invited to attend this year's star party, as my daughter has recently accepted a job working at StellarVue as an assembler. She and I went and had a great time.

Regardless of this connection, I believe that StellarVue makes really fine scopes. The degree of care and inspection that goes into every single one means that every scope they ship to a customer has had personal care put into it to make sure that it performs to the highest standards. Every StellarVue scope that I've ever looked through (about 50 or 60 at this point) has performed better that what you'd expect for a scope of its size. Vic produces a quality product, in every instance, unlike other companies where the quality of the scopes varies considerably, even among different scopes of the same model. With those manufacturers, you might get lucky, you might not. Plus, extreme care is taken with the design of each StellarVue scope to give it the opportunity to be the best scope of its class that it can be.

This isn't an advertisement, it's a heartfelt personal statement. I felt this way before I knew Vic personally and before I had (through my daughter) any connection with his company. The more I've learned, the more impressed I've become and the more strongly I feel about the quality of his scopes compared to the rest of the market.

Here's a report on the StellarVue DSSP star party I've posted in the StellarVue Yahoo group, lightly edited. So if you want to see what an astronomer's star party looks like from within (to a somewhat aberrant observer like myself, anyway), here you go.

StellarVue on Facebook
Thursday

We arrived in mid afternoon after a very nice drive of about five hours. The sky had about 40% cloud cover at the time. It was bone simple to find the site, it's on a county road off a State Highway with an entrance marked with flags and banners in an area where there's nothing but mailboxes and cows along the road.

The Likely Place RV park is very nice and well maintained. The staff works hard to keep the place clean and in good shape. I was very impressed at the professionalism with which the park is run throughout the trip. At our campsite, I was astonished that though food was left out at all times we never had a problem with that. Clearly the management here has some sort of a deal with the Varmint's Unions, as there was no sign of raccoons, skunks, or bears. There were a plenitude of ground squirrels (Belding's Ground Squirrel in the campsite area, with an occasional Golden Manteled Ground Squirrel in the area), but their contract apparently does not include picnic table raiding duties.

The Likely Place RV Park. It's a very nice place to stay, the most civilized place in nature I've ever been for a star party.

If you're a bird-watcher, come prepared. The area is rife with opportunities for seeing new species or seeing ones already on your list in a new environment. Bring your bug repellent whether you're a bird-watcher or not. For about an hour a day, the mosquitos come out. We only had one really bad day (Sunday evening), but the repellent is something you'll want every evening even if there are just a few mosquitos poking around looking for unprotected targets.

At dinner we sat with a delightful group of people. The food was wonderful and plentiful. During the course of our conversation we managed to solve the problems of national defense and foreign aggression. We were at the point of enacting our plans when dinner ended and we went to the Villa for the evening's program.

The Villa is a small house at the site that was apparently built as a model for seasonal housing at the park. It's a trim comfortable little place with a big enough area for the DSSP participants to gather and watch presentations and videos and such. There's some soft seating, wooden chairs from the kitchen for those who prefer that, copious carpeted floor, and places along the wall to lean if you don't care to sit after five hours' driving, like me. Outside the kitchen door there's a patio area with a propane barbeque.

At the program we learned new information from Preston that had a profound effect on us. Those of us who had solved the problems of national defense and foreign aggression were lucky that we hadn't moved hastily, as the new information would have upended our plans for world peace. Vic followed with his own presentation. The presentation was an expose on the life of Preston. Since much of the material touched on subjects that I'm not in a position to discuss because of my work, you'll have to attend a future DSSP to find out more. Jokes aside, thanks, and my hat's off to Preston for his service to our country and the world. It was a pleasure to cross paths with him at this event.

As the sky darkened we returned to the campsite to get ready for the evening. It was looking good, as the cloud cover was at about 30% and the clear areas were quite clear. As it got closer to dark, though, clouds began blowing in to cover more of the sky. Amaryllis and I hadn't set our scopes up yet, but when I went back to open up the car to get them we started getting some sprinkles.

So I decided to take a nap instead. I stirred about once an hour, but each time I heard rain on the top of our tent so I went back to sleep. Until I once when I woke, when I noticed it'd gotten a fair bit colder, and that I didn't hear any rain.

This seemed promising, so I came out of the tent. The sky was wide open over me. I stopped. I couldn't move for a moment. Once I could move, I had been struck so hard I checked myself for signs of The Purple Death. My forehead was clear, so all seemed OK. The Milky Way spanned overhead. I immediately saw the North America Nebula standing out like a map hung in the sky. Next to it the Pelican took only a little more looking to perceive.

The Meadow, where we set up the scopes (only about half of what was later set up is visible here.) Look at how the sky gets really dark as you go up.

I went out to the meadow where we had set up scopes (now under cover) for a better look. The north was clear to the horizon. A few stray clouds were to the east, the west was clear, and some clouds covered the lower 20 degrees of the south, but it was clear to the southwest. I would have gone for my scope, but my feet were rooted to the ground by the incredible detail of what I was seeing with my eyes. To the north, the Double Cluster stood out bright enough to be distracting. It was so bright it was hard to look away to find other objects. It wasn't possible to distinguish the two clusters as separate objects, but they formed a sort of figure eight shape in the sky.

The Little Dumbbell was visible by eye, as was the nebulosity around M103. When I looked up at the Little Dipper, I saw that the sky was around magnitude 6.5 to 6.8 (the moisture levels in the air were quite variable.) The Dumbbell was barely visible by eye, and M82 was visible to averted vision but not direct vision.

As time went on others stirred and joined me out on the field. We had a very pleasant conversation while enjoying the incredible sky overhead. At any given time, there were four of us out there--exactly who changed over time. At least two of us tried using binoculars, but we learned that any optical instruments other than eyeglasses would fog over immediately in the high humidity. Fortunately, the sky was amazing enough without anything other than our eyes.

The south cleared around 2:30-3:00 and Scorpius and Sagittarius came out to play. M8 and M20 stood out like beacons. M22 and M28 were easily visible. M7, like the Double Cluster, was bright enough to be distracting. It's shy sister, M6, was an easy catch by eye. I didn't count the number of DSOs I could see by eye over the course of the night, but it was on the order of fifty or more.

Finally, dawn came and sent us all to bed.

Friday

We went on a great hike near the campsite to see a waterfall and the site where Bigfoot had been spotted the previous year. The hike was a wonderful outing along a set of very well maintained trails. The waterfall was very impressive, thanks to the very wet year we've had in California this year. It roared and fell down a long slope, where it turned into a whitewater torrent in the gulch below. Further in we came to a beautiful lake, apparently named "Clear Lake." It made me wonder how many lakes must share that name, but it was very beautiful. It had either a beaver dam or a snag that looks convincingly like a somewhat under-maintained beaver dam at the narrow end. Further along, the lake opens up and becomes a broad expanse. The skies were light blue at the horizon but faded to the inky dark blue at zenith that we astronomers love in our daytime skies.

At the furthest point of the hike, we met some young volunteers maintaining the trails. They were apparently let loose to work in the area without being fully apprised of some of the local hazards. Vic told them a story from the area that reminded me strongly of the Calaveras County Monster story I was familiar with from further south in California's high country. Hopefully they were able to use the information.

Vic's dog, Buddy, a trained Bigfoot tracker, didn't pick up much of a scent until we were on our way back. About that time we started hearing a grinding sound in the distance. Buddy seemed to pick up some scent near the trail. He cast back and forth, but apparently wasn't able to pick up the direction it led. Bigfoot is notorious for being able to throw off trackers, and it looked like Buddy was beaten, this time. Vic informed us that the grinding sound we heard was Bigfoot grinding tree limbs against each other as a way of warning intruders off its territory. I saw what appeared to be some clothing stuffed into the crotch of a tree about 25 feet off the ground near where we were. I couldn't tell exactly what it was, but through binoculars it looked like at least part of it was a barbeque apron reading "Virginia is for Lovers."

Buddy, the trained Bigfoot Tracking Dog, visits with astronomers. The scope at left is a home made 6" Dobsonian, the one behind it is one of StellarVue's incredible 130mm refractors. In the background you can see a 24" Dobsonian and at right a 90mm StellarVue refractor (a perfect beginner's scope, which I highly recommend!)

After we returned to the cars, we were all ready for some lunch. We returned to the camp where we all put together a magnificent lunch at the Villa. Mavis provided meat for barbeque, there was a salad and plenty of other great food. Amaryllis took charge of the grill and cooked up hamburgers and polish sausages. She later chided me for letting her leave the house without her usual seasonings for grilled burgers, apparently I thought her opportunities for using them on the camping trip when we weren't bringing hamburger ourselves would be limited.

During lunch a solar scope was set up, and there were solar prominences and sun spots to be observed. Since these have been missing for the past two summers, there was much rejoicing.

After a nap, I got together with the others for another spectacular dinner at the park's restaurant. At the table I was at, we discussed the weather and prospects for the evening alongside solving the problem of world hunger or something like that. I forget exactly, as that night's presentation at the Villa has muddied my recollections. Jon showed us the results of his work in astrophotography. The images are best described as "life-changing." If it hadn't been for the fact that we had to see the images through a less than perfect system of reproduction, I think we would all have been translated to a higher state of being about halfway through the presentation. Amazing work, Jon! Thanks.

When we came out, the sky was leering at us with a cloud cover of about 20% and the sort of smile that you normally see on a car salesman when your car pulls up in front of his lot with a shuddering stop and a cloud of smoke. We didn't know what to expect, but hoped for the best. I decided to plan only "unstructured" observing. I didn't make up a list of objects, I just decided to see what was up and look at it when it appeared.

The good sky held through the early parts of dusk. We got our equipment out and set up, and started observing the early objects like Venus, Mars, and Saturn. Then a cloud began to grow out of the air. Directly above us. Other clouds appeared out of the air at some distance from us, but not near the horizon. When I walked from the meadow to the parking area, the sky was clear. Back at the meadow, the cloud clung to the zenith. As I looked around, I realized the clouds were forming over the grassy areas. The meadow and each of the links of the golf course had their own cloud directly overhead. There were still things to see, but there were those darn clouds blocking about 70% of the sky from where we had our telescopes (except for some of the folks who went up on the nearby hill to do some astro-imaging. They were probably laughing at us and throwing things into the cloud to try to get us to add to those stories of rains of stones and fish that Charles Fort liked to collect.)

As it reached full dark, however, the clouds began to diminish. A few of the clouds in the distance hung around and circled us, laughing as they blocked this small bit of sky or that. But the cloud overhead cleared and we got our sky as dusk reached its end. The seeing was pretty poor for the first half of the night, but the air stilled in the early morning about the time Jupiter came to the party. Overhead I could make magnitude 6.5 by eye when I checked, there were times during the night when it was better but I didn't measure.

I spent some time with my scope, but more time looking through other people's instruments. The 20" Dob showed M51 with incredible detail. Detail within the dark lanes was visible, with about four turns of spiral arm immediately visible. I got a view of M82 through one of the StellarVue 115mm scopes that showed its center looking like whipped cream on coffee. The sharpness of the image and detail for that aperture were incredible. Every time I looked through one of the 115mm scopes I had to wipe the drool off my chin afterward. The clarity of detail they give is nothing short of amazing. At the time I didn't know there was a distinction between "old" and "new" 115's, so I can't say anything about relative quality except that every single one did things I didn't think a 115mm scope could do, and I say this as someone who has a 90mm scope that can pick up the eyes in the Owl Nebula.

Saturday

After a gigantic breakfast of some of the best biscuits and gravy I've ever had short of my wife's, Amaryllis and I joined Vic and Jan for riding a couple of hours of driving around the park's golf course on a cart. We had another family with us on two carts. I remember the names of Mavis, Anthony, and Josh but I'm afraid I've forgotten "Dad's" name. I've just slapped myself for this, since he and I spent a lot of time talking together through the whole time there, having some of the best and most stimulating conversations imaginable. They were up from Reno, and were a highlight of the DSSP for us. Amaryllis was pleased to not be the only younger person there, and they were pleased to have her there, too. Anthony and Amaryllis were observing buddies, sharing time on her telescope. During the party they independently discovered M25 and M28 together, and spent a lot of time hanging out and talking about things people over 20 wouldn't get.

During our time driving around the golf course we got to enjoy the park's beauty and some of the local wildlife, as well as Vic's amazing driving skills. I probably shouldn't say this here where he can see it, but speculation outside his hearing has it that he was a leading NASCAR driver under another name, before some tragedy drove him out of the business and into the relatively quite pursuit he's in now. Anthony received some valuable training from Vic, though, and shows promise as a driver himself, based on what I saw.

We saw a number of gopher snakes around the property, but no rattlers at all, which is really good (gopher snakes displace rattlers in the environments they inhabit, typically.) There were also some wild turkeys (the feathered variety, not the bottled kind), ducks, flycatchers, and, when we returned to the restaurant, well--I'll leave that bit of wildlife a surprise for anyone who goes there. It was surprisingly hard to see, but calmly sitting under a tree.

At dinner that night they served us local beef, New York steaks that were very tender and cooked as you like. Over dinner we solved a number of persistent medical problems that have plagued mankind since antiquity. The answers were amazingly simple, and I wish I had taken notes, but they may be lost until we can get the same brain trust together again.

Rather than napping as I should, I attended the astrophotography session. Since my work is instrumentation, it sounded a lot like my work, except for bits that sounded like the astrophotography. I used to do astrophotography back in the days when we used to slap some egg albumin and silver nitrate solution on a stegosaurus skin and hope for the best. I can tell I'm not ready to take up digital astrophotography for myself just yet, and I have an even deeper respect for those who do it. Those who see the shift from emulsions to digital technology as a sort of "easy way" or cop out compared to film and darkroom work have no clue. The skill and art it takes to produce great astrophotos is every bit as great as it takes to get a film shot with less data and beauty in it. Again, thanks to Jon for this session.

The day was less humid than Friday, but we'd learned that the sky here held more tricks than we knew. So as it got dark we were all wondering what we'd actually get. At dusk, there were only a few clouds, less than 10% cloud cover. As it was, we worried for nothing. Some high level humidity made the sky background not as dark as it could be, but there was nothing blocking our view except for a few small clouds poking around the horizon.

This evening I'd opted for a more structured observing plan. I decided to see how many Messier objects I could catch. I knew this would leave me with plenty of time between bursts of activity to socialize and catch views through other people's scopes. I was starting to put together a plan in my head and write a list of what wouldn't be visible when I decided to ask George Robinson his opinion on M48's visibility. George has run several local Messier Marathon groups and is a veteran of =the= Messier Marathon in Arizona. As it turned out, he whipped a list out of a notebook that had an observing plan for this time of year, from one of Don Machholz's books (get Don Machholz's book on the Messier Marathon if you don't have it, even if you don't plan on doing anything more than casual Messier observation. It along with the Kenneth Glyn-Jones books are my favorites on the Messier objects.)

I taped the list to the tube box of my home-made 8" dob and worked my way through it over the course of the night. I worked my way up from the Beehive to the Leo galaxies, then trudged painfully through the Virgo galaxies (I only really learned my way through them last year, after many years of trying to learn them under pristine skies, I found out it was far easier to learn them under so-so skies that wash out all the background galaxies.) Once I was through them I took a break. I kept up the work a while, break a while routine through the night. I had a great conversation with Vic during the early hours. Vic actually stayed up later than George Robinson that night, for the record. As dawn approached, I ended up being the last person out on the field as I was trying to catch M74, M77 and waiting for M45 to appear. The list I had from George showed the clusters in Auriga as well, but the list was for "late June" and I could tell that they wouldn't really be visible for another week or two.

I misjudged the location of Jupiter in Pisces, so I couldn't catch M74 before dawn. I would have given up on M77, but the fact that I was waiting for M45 kept me at both it and M74. Finally, with averted vision and by jiggling the scope I managed to catch M77. I moved off it and came back again from a different direction to make sure I wasn't seeing things. I found it again, it wasn't just a floater in my eye. Then I walked back and forth across the field, blocking the light on the edge of the horizon with my arms, looking for M45. I kept changing where I was hoping that I'd see it from one side of the field if I didn't pick it up on the other. At last, I thought I could pick out Atlas and Alcyone. I ran back to my scope and confirmed it, I picked out the bright six and about four or five dimmer stars from the group. So I got 94 Messier objects for the night, a new personal record for myself, over 20 more than ever before. There was only one object that was possible that night that I missed, M74. The sky was too bright to see any stars in Auriga, even Capella was washed out.

The sun then chased me to bed. Only Mercury and Jupiter were visible as it rose.

Sunday

By Sunday I was barely able to stand on my feet. I was lurching rather than walking, and I spent most of the day in a chair trying to shove my brain along with a forked stick as I logged the prior night and laid plans for another. Conversation was a lot easier to manage, so I spent some time working with the group to solve humanity's needs for energy. We attacked the problem from both the personal, ground-up level and the general top-down approach. Once I realized we were having two different conversations and I stopped being contentious, we managed to find a wide range of solutions at all levels. Somehow time got away from us and we forgot to take sufficiently clear notes. Fatigue left me putting long rips into the paper with my pen when I tried. I'm sure that when we get together again we'll manage to fill in the gaps and come up with a plan to present to the world that will be heralded as genius in its simplicity and elegance and provide everyone with everything they need as well as opening up space travel to everyone of any means. The areas where my notes are legible sound promising.

At dinner, the group I was with this night had an interesting dynamic. As we each shared our own knowledge and experience, we discovered a hidden code of secret knowledge within forgettable works of science fiction. Behind the facade of bad dialog, impossible physics, and threadbare characterization we discovered a stream of human knowledge that has been preserved since ancient times. Behind the radio shows and serials, Commander Cody, Tom Corbett, Flash Gordon, and Rocketship XM we uncovered much that we already knew, including Integral and Differential Calculus, basic laws of sociology, and fundamental knowledge of human organization. When we each shared our viewpoint, we realized that we were able to describe within what we knew the forms of science that was not yet codified in conventional form. Unfortunately, dinner ended, but we've committed ourselves to continuing our investigation after we get home and get more sleep.

The evening's presentation of science fiction humor only added new questions to our search. Like, where do people get the time to come up with this stuff? I'm sure the answer is out there, if only we watch more old S.F serials and listen to more old time radio programs.

When night came, I was barely on my feet. I helped my daughter sort out a problem with her mount at the outset. Once she got me to shut up and do as she told me, we had it sorted. We were both beat, though, so about 12:30 we decided to pack it in and just enjoy other people's scopes.

Prior to that I had the chance to experience Saturn and the Veil through Inge's 165mm StellarVue scope. Saturn was huge and gorgeous. The view of the Veil was like nothing I have ever seen through any scope ever before. It looked like a ribbon of thick oil on water. The sharpness and detail were amazing. I say the Veil through the 24" that same night, and in the 24" it looked three dimensional. Which view was more amazing? I couldn't say. But I have seen the Veil look as is looked through the 24" in other large instruments. I have never had a view of the Veil in an instrument under 18" as astounding as what I saw in the 165. I have never seen it look like that before. The gaps looked like rips in shiny fabric, the subtlety of the shading was beyond description.

Seeing the whole Veil in a 115 was another experience. It was clear, sharp, and bright. It didn't take looking to see, it was just _there_, in its entirety. Another unique view.

After my daughter and I packed up our scopes, we realized that we couldn't walk well enough to trust ourselves around other people's scopes, so we turned in. We made vague noises about getting up once we'd rested a bit to enjoy the rest of the night, but Mr. Sandman had other plans for us.

Monday

Monday morning was bright and clear. If I'd resembled something more alive, I might have considered extending my stay. As it was, I had to restrain myself from demanding "Braaaaiiiinnnnnssssss" for breakfast. Breakfast and the subsequent conversations were very invigorating, though (for the record, I reduced my food demands to chicken-fried steak and eggs.)
Amaryllis was a big help in packing the car (she packed up the campsite while I talked to Vic and Gordon), so I drove the whole way home while she read and napped. The driving was great, except for the parts on California highways near Reno where interminable construction projects exist to keep Californians from going to gamble anywhere but to Indian casinos that pay California taxes.

Now I've managed to finish my logs (and this message) and I'm ready for next year. I'm hoping we can get the whole family there.

Note that I didn't take formal logs of anything on the trip outside of my astronomical observations, so anything above that's not strictly astronomical only comes from personal recollection. Other persons in the same place at the same time may recall something else entirely. In fact, I'd be surprised if they didn't, based on some of what appears to be hidden within the backstory of "Flash Gordon Saves the Universe."

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What Can I See with My Telescope: Saturn

2010-04-12T16:37:00.000-07:00

Saturn is one of the things in the sky that you can see through a small telescope that is just as impressive as it looks in the photos you see. While many deep sky objects, such as nebulas and galaxies, do not look as impressive as in the books and magazines, Saturn does.

Not only that, there is something special about the way it looks that makes it look different than any photograph or video. When you see it with your eye, it's special. Just like the Grand Canyon, it has to be experienced to be appreciated.

Astrophoto of Saturn by amateur Rochus Hess

As I write this, Saturn is a bright star visible in the early evening sky. To find out whether it's visible as you read this, visit one of the free on-line star charts, such as those listed to the right.

What to expect with:

7x35 to 8x65 Binoculars: A bright object that looks somewhat different from a star. It will be steadier than most stars, and a pale yellow in color under most skies. You will also be able to see 2-3 small companions as points of light. One will be brighter than the others. These are satellites of Saturn, the brightest is Titan. Saturn itself will not show a disk with small binoculars, but sometimes it will look misshapen as a result of the rings.

60 to 90mm Telescope: At 50 to 100 powers of magnification, you will have a nice view of Saturn and the area around it. You will probably see 1 to 3 satellites, the brightest of which will be Titan. The rings will be easy to see. At 150 to 200 powers, look for the shadow of the rings on the surface of the planet, under good conditions it will appear as a thin black line. Careful looking with a relaxed eye should show the bands in the atmosphere of Saturn. Some bands will be yellow, others will be white. They will go from side to side across Saturn.

4.5 to 6 inch Telescope: Far more detail will be visible at powers of 150 to 200 times magnification than with a 60-90mm telescope, in most cases. Also, more moons will be visible, as many as five under the best conditions. From brightest to dimmest they will be Titan, Iapetus, Rhea, Dione, and Tethys. Tethys is a difficult find with a 6" scope. Titan will almost always be the brightest when it is seen. Iapetus, Rhea, and Dione are hard to tell apart. There's a Saturn Satellite Finder on Sky and Telescope's site, since you can't tell your moons without a program.

Saturn itself can show a lot of detail. The best way to see it is to stay at moderate magnifications for this scope size (150-200 powers) and look with a relaxed eye. Give yourself time, be seated if possible, and use a scope that tracks the sky with a clock drive or computer if possible. See if you can see the bands within the light bands of Saturn's atmosphere. Enjoy the rings, the break in the rings called the Cassini Division should be obvious with good optics.

7" to 9" Telescope: At this point it's possible for Saturn's features to be washed out by how much light your telescope collects. However, telescopes in this range are excellent for observing Saturn. Start at low powers (50 to 100x) and observe Saturn and its neighborhood, looking for up to 9 moons (see the section on 4.5-6" scopes). Then move up to moderate magnification, about 150 t0 200 powers. At this point you may need to actually block off some of Saturn's light to see fine detail. There are many ways of doing this. My favorite simple methods are to either partially block the light coming in to the telescope with my hand, or do the "hat trick" by blocking some of the light with my hat.

By moving the object you are using to block either more or less light, a little at a time, details can come out for you that would not either without some of the light blocked, or using a light blocker that sits still.

With this size of scope, you can take magnification up to 300 powers or more. Most scopes will give the best views at 350x or less, some can go up to 450x before the image degrades. As the magnification goes higher, the problem of too much light will be less of a problem. However, at higher magnifications you'll need to have some means of tracking the sky, or you won't be able to see much of Saturn before needing to move the scope to follow it across the sky.

Larger Telescopes:

Larger scopes can be used in the same way as 8" telescopes. The only advantage to larger scopes is that they can see more detail within the detail, and can pick more detail out of the rings of Saturn. They are more sensitive to washed-out images of Saturn than scopes in the 7-8" size, but when properly "masked off" they can provide sharp, stunning views. Fine detail that larger scopes can pick up includes "clouds" in the atmosphere of Saturn, streaks in the atmosphere, more detail at the edges of the different bands in the atmosphere, such as swirls, and of course the dimmer inner rings of Saturn. Very well designed scopes of smaller size can pick out these details under excellent viewing conditions, but with a larger scope it's easier to do under less than optimum conditions.

Meteors, Meteorites, and Meteoroids

2010-04-09T11:38:00.000-07:00

Meteors, or falling stars, are a common and wonderful sight in the sky. It doesn't take any special equipment to see them, or any special training to enjoy them. They can be seen anywhere that the sky is dark enough for them to show. In some cases, extremely bright ones have been seen in daylight!

Meteors are small objects falling into the Earth's atmosphere from space. Just as spacecraft returning to Earth are surrounded by brightly ionized air due to the friction of the air with the falling spacecraft, the small object is surrounded by brightly lit air, caused by the friction of its entry into the atmosphere. The light mostly comes from the heating of the air. Little or none of the light comes from burning of the meteor itself, normally, though there are some types of meteor where there can be more burning of the material than the norm.

Meteoroids

The objects in space are called meteoroids, before they encounter the Earth. They are not a special class of objects, it's just a general term for small objects like bits of dust, small rocks, and so on. They can have a number of sources.

Meteors

The term meteor refers to the event of the meteoroid passing through the atmosphere. This is the show we get to enjoy. As an event, it has a name, just like "rainstorm" is a name for an event. It's not a name for a "thing", so to speak.

Meteorites

A meteorite is a thing, on the other hand. It's what we call the material of the meteoroid that reaches the surface of the Earth.

Chondrite

Chondrites (pronounced kon-drites) are the most common meteorites. They are remnants of the earliest material that formed in the solar system around the Sun. The name chondrite refers to the chondrules (kond-rools) that they're made of--little blobs of rock.

Close Up of a Chondrite, Showing Chondrules

Chondrules Rubbed Out of a Chondrite

One type of chondrite is rare among chondrites, this is the Carbonaceous Chondrite. The name refers to the fact that it's got a lot of carbon in it. This gives it a black color. Carbonaceous condrites are the earliest of the chondrites.

Carbonaceous Chondrites

All chondrites come from small bodies that formed in the early solar system that never got large enough to form enough heat to melt down the various materials that they are made of, and separate them. For example, in the Earth the materials it was made of did melt. The iron and nickle and other heavy metals sunk to the center of the Earth for the most part, and the lighter "rocky" materials stayed in the Earth's outer crust.

There are meteorites that come from larger bodies that did melt and separate the materials that are all mixed together in chondrites. The ones that were once in the core of these larger bodies are the iron meteorites.

Iron Meteorite

Since most iron meteorites formed in a much smaller body than the Earth, the iron in them cooled in an environment where the metal formed large crystals that can only form in a low gravity environment where cooling is very slow. Iron meteorites can be cut, polished, and etched to show these beautiful crystal patterns, known as Widmanstätten or Thomson patterns.

Crystal Patterns in Iron Meteorite

Some meteorites are pieces of larger bodies in space. Pieces of the Moon and Mars have been identified. These meteorites are the result of a meteorite hitting the Moon or Mars hard enough to knock pieces of them off into space!

Some are pieces of asteroids. One type of meteorite, called a Pallasite, are believed to be pieces of the asteroid Vesta. They are especially beautiful, and are often turned into jewelry.

Pallasite

Don Machholz Discovers Comet Number 11

2010-03-29T15:40:00.000-07:00

My friend and neighbor Don Machholz has discovered his 11th comet! He searches for comets using telescopes at his house, either on his deck or in his backyard observatory.

See the announcement here: http://www.thecomethunter.com/

Don's web site is a wealth of information, on comets as well as on general astronomy. Don runs well organized star parties and is one of the pioneers of the Messier Marathon, a special star party where participants try to see as many Messier objects (from a list of 110) in one night. Among the things you'll find there are a free download of one of Don's books, A Decade of Comets.

Don has had to develop a technique to give himself the best possible chances of discovering comets "by eye" to beat the space-based and other professional instruments to the discovery. Anyone with an interest can be a comet hunter, however, and Don shares his techniques. In one case recently, a German amateur astronomer discovered a new comet by happenstance while trying out a new telescope.

What Can I See Tonight?

2009-08-15T12:59:00.000-07:00

This summer I was at a star party, showing the sky to interested non-astronomers, as I do many nights each year. One participant came armed with the knowledge of a number of the finest objects to view in the sky. They asked me to show one, then another. They and the others there all enjoyed seeing each of these objects as I put them in the telescope's view.

Then they said "How about the Orion Nebula? I hear that's really beautiful!"

It is, but I couldn't show it to them. I had to apologize, then explain that we couldn't see Orion that night.

Why?

The Sun blocks part of the sky from the Earth's view. Here, the area near Pisces is behind the Sun. Image by Tau'olunga.

As the Earth travels around the Sun during the year, there is part of the sky behind the Sun that is not visible. The part of the sky that is behind the Sun from our point of view changes depending upon where we are in our orbit. In the image above, Pisces lays on the far side of the Sun from the Earth. The other constellations nearby will also be hidden since they are only visible during the daytime. Pisces would be high in the sky at noon, but you can't see stars at that time because the atmosphere will be lit by the Sun.

Even if you were outside the Earth's atmosphere, there will still be stars hidden behind the Sun. But you would be able to see more of those close to the Sun since the Sun's glare wouldn't be spread out the way it is when you're looking from within the atmosphere.

Six months later, the Earth is on the other side of the Sun. At that time Pisces will be high in the sky at midnight. But the stars in Virgo and the area around it will now be hidden by the Sun.

The Orion Nebula. Impressive, but don't expect to see it in summer. Image by Filip Lolić.

Orion is called a "Winter" constellation because it is highest in the sky at midnight during winter. It's close enough to the ecliptic that it's hidden by the Sun during summer. That means the nebulas in it, including M-42, the Great Orion Nebula, will not be visible in summer. They are visible at other times of the year. Though only in winter are they visible at relatively convenient times of the night, near sunset. At other times you'll need to either get up early or stay up late.

There's a myth about Orion and Scorpius. It's said that they were mortal enemies and would always fight. In the sky this is reflected by the fact that they are at opposite sides of the sky, and are never in the sky at the same time. So, while Orion cannot be seen in summer, the wonderful sights of Scorpius are not visible in the Winter. So if Scorpius is up, Orion isn't, and vice versa.

The M-4 Globular Star Cluster, in Scorpius. See it in the summer, you won't be able to in the winter. Image by Ole Nielsen

How much does the sky change each night? A reasonably accurate rule of thumb is that the stars rise three minutes earlier each night. Note that this doesn't apply to the Moon, it moves in an entirely different way, coming up about 40-some-odd minutes later each night. Another rule of thumb is that the sky changes by about 1 degree each night. This is because the Earth moves about 1 degree in its orbit about the Sun each day. This means that something that is up tonight by about 10 degrees above the western hemisphere will disappear in about a week and a half. So see it while you can!

Likewise, if you see the Pleiades just above the horizon at sunset, you have less than an hour to wait before the rest of Taurus, including Aldebaran (the Eye of the Bull) and the Hyades (another nice star cluster in Taurus) are visible.

Galaxies

2009-07-25T03:21:00.000-07:00

About a century ago, it was thought that everything that existed was within a few thousand light years of us. (See How Far? for an introduction to astronomical distances.) Our Sun was known to be one of many suns in the midst of a large structure made up of stars, collections of stars in the form of star clusters, and clouds of gas and dust called "nebulas" after the Latin word for cloud.

There was one class of nebula that was particularly interesting to many scientists. They were known as "spiral nebulas." One reason that these were of particular interest was that they were seen by some as new solar systems in the act of creation. Scientists such as LaPlace and Gould had developed ideas about how systems of planets like ours could come into existance. If the spiral nebulas were new planetary systems being formed, studying them would give the scientists more information to choose from the available theories and enough information to refine them or develop new theories.

M-51, known as The Great Spiral Nebula until about 80 years ago.

The shape of the "universe", as it was seen then, was pretty well known. The Milky Way, a band of light across the sky, had been recognized long before as being made up of stars. It was known that most of the stars lay in a more or less flat circular area, shaped like a plate. It was also recognised that there were more stars in the direction of Sagittarius, and that they extended over a larger area than the thin plate, there was a bulge. It was thought that this was where the center of the galaxy lay. This last wasn't apparent at first, since the stars at the center of the galaxy can't be observed directly from Earth. There are dark nebulas between us and the center of our galaxy, otherwise we would see a huge globe of light when we look that way at night.

In ancient times the Milky Way was thought to be a cloudy mass. When Galileo turned his telescope on the Milky Way about 400 years ago, he saw that it was individual stars in such great numbers and so faint that they blend into a cloudy mass when viewed without a telescope. The spiral nebulas did not look like stars, though. They looked like clouds, even through telescopes.

What Is It?

In the early part of the 20th century, some scientists felt that the spiral nebulas were not as close to us as other stars. They felt that they could not be new solar systems forming, because they were so far away that they would have to be many light years across, far larger than out solar system. Finally, it became possible to measure distances to the spiral nebulas. The distances were shocking to those who saw our universe as being a few thousand light years across. The distances to the spiral nebulas were in the millions of light years.

Further study determined that the spiral nebulas are made out of stars. They are so far away that they don't resolve into stars as easily as the other known star clusters that are only hundreds or thousands of light years from us. At first, these other bodies of stars so far from us were called "island universes." But this was a mis-use of the word "universe." The word universe implies everything. There can't be more than one "everything." If they were there, they were part of "everything", too.

Up until that time the word Galaxy had been the name for the Milky Way (which is what the word means.) It got generalized into the common noun galaxy as a word for these other groups of stars millions of light years away, and the word universe went back to meaning absolutely everything. Though today the word universe gets misused as a way of describing other sorts of places that you can get to in mystical or science fictional ways. The rule is, though, that if you can get there or interact with it in any way, it's still part of the same universe. The only way something can be another universe is if there's no possible way to have anything at all to do with it.

How Far Can You See?

One galaxy outside our own is commonly known as being visible to the eye. This is the Andromeda Galaxy. While all the other stars, planets, and cloudy patches you can see in the sky with your eyes are from a few light seconds (the Moon) to a few thousand light years away, the Andromeda Galaxy is about 3 million light years away. It's a fuzzy patch in the constellation of Andromeda. It doesn't look like much, in fact it's hard to see if you look directly at it unless you're in a really dark area with good skies for astronomy overhead. It shows up a little better if you look a little bit away from where it is because our eyes are more sensitive to slight differences of light a little off center of our field of vision.

A photograph of the Andromeda Galaxy from 1888. At the time Andromeda was thought to be a nebula within our galaxy.

Occasionally other galaxies can be seen if your eyes are good and the sky conditions are really, really good. I've seen the Triangulum Galaxy by eye, which is a bit further away than the Andromeda Galaxy.

Both these galaxies are close to the Milky Way, relative to many other galaxies. They're both part of what's called the Local Group of galaxies. A small telescope can see many more, also quite close to us, but also many that are outside the Local Group.

How Many Galaxies Are There?

Look at all the stars you can see in the sky. Now look through a telescope. There are about 100 million stars in our galaxy, scattered like glowing sand across a black sheet of paper.

There are more galaxies that we have seen than there are stars in our galaxy, however. There are well over a billion galaxies. Everywhere that we look where our view of deep space is not blocked by something in our own galaxy, we see countless other galaxies.

Everything in this photo that doesn't have four little 'diffraction spikes' of light coming from it is a galaxy.

The picture above occupies an area of sky so small that the tip of your finger held at arm's length would cover it with plenty of room to spare. Galaxies are scattered across the sky like this in all directions.

What Are Galaxies Made Of?

There's nothing mystical about the other galaxies in our universe. They are made of the same stuff as our own galaxy and the same stuff we see here on the Earth. They have the same elements in them, and they are made up the same way. Just because they are far away doesn't mean that they have different rules of physics than us. We see the same physics there as we see here on Earth.

They are very interesting, though. Just as you have to go to special places on the Earth to see a tall waterfall, there are special places in the universe that are unusual and beautiful.

To see more interesting galaxies, and take part in doing some galaxy science yourself, visit the Galaxy Zoo. You can see lots of interesting and beautiful galaxies there, learn something about how they are classified, and help with classifying galaxies yourself. There are so many galaxies that there aren't enough astrophysicists to study each and every one. So members of the public have been called upon to help! Head on over, and give it a look.

Daytime Observing with Your Telesccope

2009-07-03T12:08:00.000-07:00

You can get plenty of use out of a telescope for astronomy even if it's not dark out. First, it's important to not use your telescope to look at the Sun unless you've got the right equipment. That means a full-aperture solar filter for starters, removing any finder scopes from the telescope, and a good knowledge of what you're doing otherwise. Those little solar filters that screw onto the eyepiece are not safe. They can crack from the heat of the concentrated sunlight on them, and if you're eye's there when they do crack, you'll get the full force of the sunlight it lets through on your retina. Not good.

There are plenty of things to look at other than the Sun, however, that don't require any special preparation of your telescope. The Moon is often up in the daytime, and while it doesn't show its detail as sharply through a daylit sky as at night it's still very interesting to look at. Just as at night, the best area to look is along the line between the day and night parts of the Moon, what's called the "terminator".

Several planets can also be observed during the daytime. Mercury is always close to the Sun, and Venus never gets too far away. Finding them during the day is the problem since they don't stand out as well as they do at dusk or in the night. If you have a chance, it's good to get familiar with where they are when you can see them easily, before you go out to find them in the daytime. Use their location with respect to the Sun as a reference, since that'll be your biggest signpost in the sky during the daytime.

Then, when you go to find it during the day you can start out with the end of the telescope covered, as well as any finder scopes. Start at the Sun, then move away from it. Stop before you get to where you think you need to be for the planet, uncover, and then move toward the planet while moving away from the Sun. Never move back toward the Sun while you're looking through the scope. It's also a good idea to have a second person on hand to make sure you don't move the scope back toward the Sun while looking through the telescope.

If you've got a computer on your telescope, that can put you on the planet once you get it aligned. If you have an alignment procedure that will work with you levelling the scope, setting it to north, and using the Sun as a reference point (line up the scope with the Sun with the covers on it and the finder--use the shadow of your scope to line up on the Sun, and don't look through it!)

Venus can show very nice phases during the day, looking like a little Moon.

Jupiter and Saturn can be seen during the day as well, they look like ghostly versions of themselves during the day. Seeing them during the day is quite an experience.

You can also see the brightest stars during the daytime. Sirius, the brightest star (other than the Sun, of course), is the easiest to see. Arcturus, Fomalhaut, Betegeuse and Rigel can all be seen in daylight as well.

You'll want a clear sky, with as little moisture as possible. The deeper the blue at the highest point in the sky, the better your chances.

Give daytime observing a try, and see how many "night time objects" you can collect!

Globular Clusters

2008-07-14T09:44:00.001-07:00

Drawing of Hercules Cluster M-13 from Recreations in Astronomy by H.W. Warren, D.D., 1896

Globular clusters are briefly mentioned in Star Clusters. They are groups of stars that are held together by their mutual gravity. They tend toward a globe shape overall, which is why they're called "globular." The number of stars in a globular cluster ranges from a few thousand to a few million in the largest ones.

Globular clusters are like mini-galaxies. They orbit their host galaxy, but to some degree are separate from it. The globular clusters in the Milky Way orbit the core of the galaxy, or around the rim. This means that they are well distributed through the sky, but lots of them are visible when looking toward the center of the galaxy (in Sagittarius, the Archer.)

Bright, Easy Objects

Globular Clusters are bright and easily seen even on nights when other objects like galaxies and nebulas are washed out by moonlight, light overcast, or city lights. You can see them in binoculars, it doesn't take a telescope to enjoy them. I had a hobby for a couple of years of seeing how many globulars I could see with 7x35 binoculars. I collected over 40 before I got a new telescope and stopped looking regularly.

Any telescope with a good mount can do a good job of showing off the bright globular clusters. If you have a telescope of 12" (250mm) or greater aperture, you can observe globular clusters in other galaxies as well as those in the Milky Way. The Andromeda galaxy (M31) and the galaxy in the Triangle (M-33) make good targets for extra-galactic globular hunting.

What to Look For

When you observe a globular, it's interesting to look for a few things. First, see how far out the globular's stars appear to go. Then, notice how quickly the cluster seems to go from outlying individual stars to the tight, dense knot of stars at the center. This is called the "condensation" of the cluster. Does it condense rapidly, or slowly, or does it have scattered stars up to a certain point then suddenly appear to become a solid globe of stars?

Next look at the overall appearance of the globular. Does it have wispy tendrils of stars? Does it look like a patch of mist? Does it look like a glowing ball of jewels? Or what?

Makes notes of your observations. It's interesting to compare and contrast different globulars, as well as to see how different they appear in different observing instruments.

Famous Globulars

Here are a few of the globulars most popular with amateur observers:

M-13, the Hercules Cluster, is visible with just your eyes under dark skies. It's in the Keystone which makes it easy to find.

M-2 in Aquarius is a beautiful object in binoculars or telescopes.

M-4 in Scorpius is also visible in a dark sky, it's near Antares, which makes it easy to find.

Omega Centauri is large and bright. It lies far to the south for mid-northern latitudes, but is a great object for binoculars and telescopes when it is visible.

Globular Cluster M-80, one of the densest clusters.

Star Clusters

2008-07-12T14:41:00.000-07:00

There are two types of star clusters, "open" clusters and "globular clusters." Globular clusters are like mini-galaxies. The gravity of the stars in them hold them together and pull them into a globe shape (which is why they got the name "globular.")

Open clusters are clusters of stars that were formed together and are still near each other. The mutual gravity of the stars usually isn't enough to hold them together, so the stars in open clusters gradually drift away from each other as they follow their own path through the galaxy. For the several million years that they are near each other, they can make a beautiful sight in the sky here on Earth.

The stars start out near each other as a result of having formed out of the same cloud of dust and gas in the galaxy. These clouds are many light-years across, and anywhere from a few to a few hundred stars can form out of a single cloud (the numbers are usually from a few to a few dozen stars.) Once stars form they blow the leftover gas and dust away from themselves. Sometimes this causes new clumps in the cloud that form into more new stars. At some point the available gas and dust becomes too little for form new stars, and it gets thin enough that the stars can be seen from outside the cloud. The leftover gas and dust may surround the young stars for quite some time, adding to the beauty of the cluster.

Here is a recent NASA image of massive star formation going on in a remote galaxy. Over 4000 new stars per year--ten times what we get in the Milky Way!

The Seven Sisters, or The Pleiades, a star cluster that's easy to see with the naked eye in Taurus. You can see some of the left over gas and dust as nebulosity (cloudiness) in this image.

How Far?

2008-07-11T18:42:00.001-07:00

When I show things off at a star party, we usually look at things that cover a long range of distances, from near to far.

Very Close: 1-2 Light Seconds Away

During the day, we'll sometimes put a telescope on a nearby landscape feature such as a mountain top or a cell tower. The distance to these objects is familiar to most people. It's usually fractions of a mile to a few hundred miles. Astronomically speaking, these objects aren't at all distant.

Close: 1-6 Light Hours Away

We also show off the Moon both in day and night. It is only a quarter million miles away. It takes light about one and a quarter seconds to go this distance, so we might say that it is just over a light-second away.

The Sun and bright planets range in the millions of miles. The sun is about 93 million miles away, planets range from a bit under half this distance to several times this distance. The distance to the sun is about eight light minutes. The planets range from about three light minutes (a very close pass with Venus) to just about six light hours (Pluto and Eris.)

Nearby: 4-25 Light Years Away

The next step in distance takes us from measurements in light hours to measurements in light years. The nearest star is a component of the triple-sun Alpha Centauri system, called Proxima Centauri. It's just over four light years away. This is about 37,000 light hours away. The nearest stars are a whole lot further away than the solar system's planets, the visible comets, the asteroids, the Moon and Sun. Sometimes in art you'll see a star shown in front of the Moon (or within the horns of a crescent Moon.) This can never happen, they are millions of times further away than the Moon. (Yes, except for our own star, the Sun. But it's still hundreds of times farther away than the Moon.)

Nearby stars include Altair, in the Eagle, Sirius in the Big Dog, and Procyon in the Little Dog. Near range out to about 25 light years away or so.

Middle Distance: 25-100,000 Light Years Away

Stars in our galaxy range from these nearby neighbors to the stars in the globular clusters. These are about as far away as you can get while still being in the Milky Way galaxy. The ones you can see can be about as far away as 80,000 light years. Most of the stars you'll see at night are far closer, however, from the nears stars above out to distances of a few hundred light years.

This range includes the nebulas, like the Ring Nebula, Orion Nebula, and Lagoon Nebula. It also includes the star clusters.

Far: Millions of Light Years Away

Here we get to the galaxies. The nearest galaxy to ours (not counting small companions to the Milky Way, like the Magellenic Clouds) is the Andromeda Galaxy, at about 3 million light years distance. A whole bunch of galaxies in the Virgo Cluster is about 50 million light years away. These objects are all far further from us than any of the individual stars, clusters, or nebula you will see through a telescope that are part of our galaxy. Telescopes with mirrors or main lenses larger than 10 inches or so can show individual items in the closest galaxies, like the globular clusters and nebulas in the Andromeda galaxy. But normally any of these you see are in our galaxy, and normally over 100 times closer than even the nearest galaxy.

If you want an idea of what you can see in different sizes of telescopes, see What Can I See in My Telescope?

Astro Basics

2008-07-11T18:33:00.000-07:00

Welcome to Astro Basics! I'm an amateur astronomer with over 40 years of experience. I have been sharing the sky through teaching and telescopes for all that time as well. I regularly take out my telescope to public places to show folks the amazing universe we live in.

When I do this, I get all sorts of questions about the cosmos. Many of them are common questions, some of them are uncommon, but likely to be interesting to anyone who thinks of them or hears them.

I'll be trying to bring some of those things to you here.

If you're interested in information about buying your own telescope, or how to use one you've got, I recommend visiting my other site:First Telescope Guide.