The eight bright stars of the Winter Circle are easy to spot high in the southern sky about 8 p.m. this month. When this image was taken in January 2008, the planet Mars was also within the Winter Circle. It has since moved on.
Tuesday, February 10, 2009
Jimmy Westlake's Celestial News column appears Tuesdays in the Steamboat Today.
Find more columns by Westlake here.
High overhead on cold winter nights is a ring of seven of the brightest stars in the sky, an asterism known as the Winter Circle. While not an official constellation, the pattern is so striking that it tends to jump right out at you. The seven stars that make up the Winter Circle are among the 20 brightest stars in the whole sky. Having so many bright stars concentrated in such a small area is part of what makes the winter sky so wonderfully beautiful.
You can locate the first star in the Winter Circle by extending a line through the familiar three stars of Orion's belt to the lower left. This flashy star is Sirius, nicknamed the "Dog Star" because it represents the nose of Orion's big hunting dog, Canis Major. Sirius is the brightest and closest of the seven stars in the Winter Circle at a distance of only nine light years.
From Sirius, shoot a line to the upper right and find the bright blue star that marks the foot of Orion the Hunter, the star Rigel. Rigel looks nearly as bright as Sirius, but is 100 times farther away, at 900 light years. If Rigel were viewed at the same distance as Sirius, it would shine like a second sun in our sky, being visible in broad daylight.
To the upper right of Rigel is the orange giant star Aldebaran, marking the eye of Taurus the Bull. Aldebaran is 68 light years away. Its name means "the follower" because it closely follows the Pleiades star cluster as it marches across the sky.
Continue from Aldebaran by extending a line nearly overhead to the second brightest star in the Winter Circle, Capella, a yellow-giant star in Auriga, the Charioteer. Capella is a mere 45 light years away. Although it looks like a single star to the naked eye, astronomers have discovered that it is composed of the light from four stars.
Dropping down from Capella toward the eastern horizon will lead you to a pair of bright stars, the Gemini Twins, Castor and Pollux. Castor is 52 light years distant and is not only the fainter of the Twins but is the faintest star in the Winter Circle, as well. Pollux is considerably closer to us at 35 light years away.
The circle now continues to the southeast of the Gemini Twins to the star Procyon. This star's name means "Before the Dog," and it is aptly named because it rises in our sky just before the Dog Star, Sirius, appears. Procyon, like Sirius, is a nearby star, only 11 light years away.
Close the Winter Circle by shooting a line from Procyon back to Sirius where we started.
As if having seven of the sky's brightest stars in one spot weren't enough, we can easily add an eighth. Near the center of the Winter Circle is the red supergiant star Betelgeuse that marks the shoulder of Orion. Betelgeuse is far away, at a distance of 520 light years, yet it is one of the closest stars that could explode as a supernova at any time - any time in the next few million years, that is.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published around the world. His "Celestial News" column appears weekly in the Steamboat Pilot & Today. His "Cosmic Moment" radio spots can be heard on local radio station KFMU. Also, check out Jimmy's Web site at www.jwestlake.com.