Saturday, January 12, 2008
Jimmy Westlake's Celestial News column appears Tuesdays in the Steamboat Today.
Find more columns by Westlake here.
Steamboat Springs High overhead as darkness falls on cold January evenings is a tiny cluster of stars that is often mistaken for the Little Dipper. Although it does have a dipper shape to it, with a tiny little bowl and a tiny little handle, its real name is the Pleiades. It is the 45th object in Messier's famous catalog (M45), and is popularly known as the "Seven Sisters," and in Japan is called the Subaru. A likeness of the Pleiades star cluster adorns every Subaru car out there on the road!
A person with average vision should have no difficulty seeing six stars in the cluster and a bit of careful searching should reveal the seventh faint star, as well. A person with exceptional eyesight might make out as many as 8, 9 or even 10 stars with their unaided eye. How many can you see?
The name "Seven Sisters" is actually a misnomer because only 5 of the 7 naked-eye stars are sisters. The other two stars represent the parents, Atlas, the father, and Pleione, the mother. In order of decreasing brightness, the seven brightest stars are named Alcyone, Atlas, Electra, Maia, Merope, Taygeta and Pleione. The other two sisters, at the edge of visibility, are Celaeno and Sterope. A simple pair of binoculars will clearly reveal the entire family and many dozens more stars to boot!
Mythology explains that the big brute Orion the Hunter, also seen in the winter stars, was chasing the beautiful daughters of Atlas and Pleione. Zeus, the king of the Greek gods, heard their cries for help and transformed the maidens into white doves so that they could escape Orion's lustful pursuit. They flew high into the heavens and still are seen today as our Pleiades star cluster.
A more modern, scientific explanation for the lovely cluster of stars is that they were, indeed, all born as siblings from the same cloud of hydrogen gas only about 10-million years ago. There are more than 500 member stars in the Pleiades cluster, all lying about 410 light years away from our solar system. That means, when you look at the Pleiades star cluster, you are seeing it as it was 410 years ago.
Although the Pleiades stood alone as a separate constellation for many centuries, modern astronomers have included it within the boundaries of our constellation of Taurus, the Bull. The tiny cluster lies on the bull's shoulder.
On the evening of Jan. 17 and 18, the fat gibbous moon will appear very close to the Pleiades star cluster. In fact, after midnight that night, the dark edge of the moon will eclipse many of the Pleiades stars, one by one. Use your binoculars to see the faint cluster stars through the bright moonlight.
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 on the Web sites of CNN.com, NASA's "Astronomy Picture of the Day" Web site, Spaceweather.com, Space.com, Discover.com, MSNBC.com, NationalGeographic.com, and in Sky & Telescope, Astronomy, Night Sky, Discover, and WeatherWise magazines. His "Celestial News" article appears weekly in the Steamboat Pilot & Today. His "Cosmic Moment" radio spots can be heard on local radio station KFMU.