Wednesday, July 11, 2012

Hot Summer Solar Observation

Our community holds a celebration each year to one side or the other of the Fourth of July. We have a street fair, dachshund races, parade, and, usually, fireworks. Lots of locals like it because it lets them extend their Fourth of July celebration a bit and get in some extra fireworks each year.

Don Machholz organizes the local astronomers to take part in the street fair, where we take out our telescopes and show off the sky, as much as we are able, to the local community. We enjoy sharing our hobby, as well as letting them know about the other events we have going on.

Each year we have several solar telescopes out, as well as viewing planets in the daytime when the conditions are right.

Last year we weren't able to attend, but the year before that we were there, showing the sun and explaining to people that usually there are things to see there other than a featureless circle. But a featureless circle was about all we had to show. There was a bit of unimpressive detail through the H-alpha filters, but chances are most of the attendees that looked didn't get so far as noticing it.

This year was a great change for the better. There were sunspots, and prominences. Sunspots are nice since they show up in an ordinary telescope with a solar filter. We had a scope with a solar filter, plus a solar projection screen that both showed the sunspots very nicely. Viewers compared them to the islands of Hawaii.

Through the H-alpha filters there were a bunch of prominences around the edge of the Sun. Solar flares, if you will. They change with time, each lasting several hours or longer and changing their appearance over that time.

Why the Difference?

A normal solar filter shows all the different visible frequencies of light. All it does is cut the amount of light down to a level where it doesn't damage our eyes or the telescope. It's what we'd see if we could stand to look straight at the Sun and still make out any detail. Plus the telescope provides magnification that makes it look larger so that we can pick out small details more easily.

An H-alpha filter is a filter that only lets through one wavelength of light, the light emitted by one type of ionized hydrogen (that's where the "H" in H-alpha comes from, H is the symbol for hydrogen). This light is in the red wavelength for us, so the image becomes a "red and white" (as opposed to black and white) monochrome image.

This clears out other light frequencies that smear out or otherwise hide a lot of interesting detail on the Sun. In H-alpha light we can see the magnetic cells of the Sun. These cells are not like the cells in our bodies, the word cell originally meant "chamber" so it got used wherever early scientists saw things divided up into little "rooms" or "chambers".

It also allows us to see the energetic material being ejected, and pulled back into the Sun. Normally the other light hides these flares and loops and other prominences. But in H-alpha light, the other light is blocked out, allowing us to see these interesting solar features.

A Good Show, Again

So now we have a good show on the Sun again. This is likely to be the case for at least the next couple of years. Usually there are only one or two years out of each solar cycle (an 11 or 22 year period, depending on how you look at it) where the Sun isn't putting on a show. And the quiet period we're coming out of was far quieter and longer than any other I've ever experienced.

Which is nice. It's a lot easier to get people interested in what's going on "up there" when you've got something interesting to show them.