The Seven Sisters of the Pleiades

As the constellations of summer move to the "downhill" side of the sky in the west, the stars of autumn are now firmly holding center stage overhead in the early evening hours. But, just as in August when the autumnal stars began to appear on the eastern horizon, so now are the stars of winter signaling that season's approach.

We are a few days from Thanksgiving, then a month from Christmas and the official beginning of the winter season, so lets take a look at those winter stars.

First we have that wonderful little star cluster called Pleiades (PLEE-a-dees), of-ten nicknamed "The Seven Sisters."

The Pleiades cluster has been known from antiquity and has been mentioned in ancient records by the Vikings, the Chinese, the Persians, the Greeks, the Australian Aborigines, and the American Indians. The Aztecs of Mexico based their calendar on the cluster's passage directly overhead at midnight. They are also mentioned by the Greek poet Homer in both the Iliad and Odyssey, and on three occasions in the Bible.

The next time you happen to see a Japanese car called a Subaru, look at the emblem on the front grill, you will find the seven stars of the Pleiades. Funny thing though -- in Japanese it translates as "turtle."

The Pleiades form an open star cluster, which typically contain a few dozen to a few hundred stars. An estimated 1,000 open clusters range throughout the gal-axy, most found in the galaxy's disk. Another type of cluster, a globular cluster, is denser and more star-packed often containing thousands of stars. About 150 known globulars range toward the center of the Milky Way galaxy.

The Perseus double cluster, which we looked at before, is an open cluster, as is the Hyades star cluster in Taurus, which we will talk about next time.

The stars in the Pleiades are about 100 million years old (much younger than our Sun), making them relative newborns on the scale of cosmic time. The estimated 500 stars in the cluster lie about 440 light years from us. In a pair of binoculars dozens of stars come into view, making the Pleiades a superb sight. While the cluster is too big to fit into a telescope's field of view, such an instrument does bring out the blue color of the brighter stars.

The Pleiades can be seen at about 6 p.m. below Perseus, it is the small group of stars rising almost due east. Charles Messier, the noted French comet hunter, added it at number 45 on his list of non-cometary objects.

SKY WATCH: First quarter Moon on Monday, Nov. 27. If you are out watching on Dec. 3 at about 5:30 p.m. local time you will get to see the nearly full Moon occult, or go in front of, the Pleiades.

The occultation will take several hours and is best watched in binoculars or a wide field telescope.

Next time, Taurus, the Bull.