|  | | Observation Logs
| Date: | Friday, Aug 10th, 2001
| | Where: | Our usual place, in front of Cavallo in downtown Mill Valley.
| | Theme for the night: | Planets again
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Gary's log entry: |
Once Jake and I got set up this evening, we ran into a little snag -- we weren't sure what to look at! So what else is new? So we started off the evening by stunning folks with views of us looking at star charts and atlases. Actually, this got us some attention -- apparently, people are curious about how we find the things that we look at, so we got the chance to show people how we do it. I gave a short lesson on how to use a planisphere to a budding your astronomer, which was fun.
Eventually though, I figured out what to look at. I aimed my scope up at an unremarkable star called Eta Aquilae, a red giant in Aquila, the Eagle. The neat thing about Eta Aquilae is that it's a variable star. "What's a variable star?" a lot of people asked me. And I'm glad YOU asked, as well!
A variable star is a star that actually changes in brightness. There are a lot of different ways this can happen. Eta Aquilae is what's known as a cepheid variable. What that means is that the star actually pulsates. In Eta Aquilae's case, it swells up from it's minimum diameter of about 70 times the width of our sun to it's maximum of 80 times the width of our sun in a little under 4 days. Wow, that's a big star! Nobody's really sure why cepheid variable do that, but it makes for a great sidewalk astronomy story!
After checking out Eta Aquila for awhile, we noticed that Capricorn had risen pretty far up in the sky. That meant that Uranus and Neptune were in the sky! I remembered where they were supposed to be, and hunted them down in my binoculars. Jake took Uranus, and I took the dimmer, harder to find Neptune. It wasn't much to look at, a whitish-bluish faint speck not too far from a slightly brighter red star (Upsilon Capricornii), but think about it...that's one of the farthest planets in the solar system, about 2.7 billion miles away from us! At that distance, it's light takes pver 4 hours to reach us. Wow. It was pretty late at this point, and unfortunately there weren't many people to show this off to. Too bad.
After marvelling at deep space for awhile, we decided to pack it in, call it a night. We took everything down, and drove off. I'm looking forward to showing Neptune off next week!
-g.
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| | Friday, Aug 10th, 2001
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