Minnesota Starwatch

University of Minnesota

Department of Astronomy

Minnesota Starwatch for February 2005
[Starwatch Logo]

Starwatch Newsletter

Minnesota Starwatch is a newsletter describing the night sky in the Midwest.

It is updated monthly, and is produced by the
Department of Astronomy, University of Minnesota
116 Church Street SE, Minneapolis, MN 55455

Minnesota Starwatch for February 2005

This months we get New Moon on February 8th and Full Moon on the 24th. The only conspicuous planets are currently the big outer ones, Jupiter and Saturn. Saturn is high in the sky each evening, in the constellation Gemini. Jupiter is brighter but doesn't rise until about 10 p.m.

On February 20th, the Moon will pass fairly close to Saturn in the sky just after sunset. On that evening, it'll be just north of Saturn and just south of the two bright Gemini stars, Castor and Pollux. That's a good time to exercise your imagination about distances, because Saturn is far beyond the Moon, but Castor and Pollux are far, far, far beyond Saturn. Astronomers often visualize distances in terms of time that light takes to travel to them. On February 20th, the moon is 1.3 light-seconds away, which means just what it seems to: that's the time that light takes to reach us from the Moon. At the same time, Saturn is almost 70 light-minutes from us, in other words 3,000 times farther than the Moon. But Pollux, the fairly bright star just north of Saturn, is 34 lightyears away--that's about 200,000 times as far as Saturn.

Pollux happens to be the nearest known giant-type star. It's orange colored, about 30 times as luminous as the Sun, and about 10 times as big as the Sun. Most of the stars that we see in the night sky are giants much farther away than Pollux, but they're not really typical of the universe. Most stars in the universe are weak little red dwarfs like Proxima Centauri, which we simply don't see because they're too faint. Giant stars, like Pollux or bigger, are really quite rare in space but we can see them from a long way off. As for Castor, the other nearby star in Gemini, it's a famous multiple. On fairly close examination it's a double; investigate closer and we find it's really a triple; and further investigation shows that each of those three is really a double star! Thus, six stars altogether, going in complicated orbits around each other, all about 50 lightyears from us.

For fun Astronomy Outreach programs check out our Public Outreach link, or if you're interested in how you can help build the new Minnesota Planetarium, please call 612-630-6151 or visit http://www.mplanetarium.org. Como Planetarium is offering fun family shows about astronomy on a limited basis; please call 651-293-5398 for more info! This has been a Minnesota Starwatch produced by the University of Minnesota Astronomy Department.