Jimmy Westlake: The Pleiades
February 10, 2014
Steamboat Springs — High overhead as darkness falls on crisp February evenings is a tiny cluster of stars that often is mistaken for the Little Dipper. Although it does have a dipper shape, with a tiny bowl and a tiny handle, its ancient name is the Pleiades star cluster. It also is known as the Seven Sisters cluster and, in Japan, as the Subaru cluster. A likeness of the Pleiades star cluster adorns every Subaru car out there on the road.
A person with average vision should see the six brightest stars in the Pleiades with ease, and a bit of careful searching should reveal a seventh faint star, as well. A person with exceptional eyesight might make out as many as a dozen stars with the unaided eye. How many can you see?
The name "Seven Sisters" refers to the seven daughters of Atlas and Pleione from Greek mythology. Only five of the cluster's seven brightest stars are named for sisters; the other two represent their parents. These seven stars are named Alcyone, Atlas, Electra, Maia, Merope, Taygeta and Pleione. Two stars at the edge of visibility represent the other two sisters, Celaeno and Sterope. A simple pair of binoculars clearly will reveal the entire family and many dozens more stars, to boot.
Greek mythology explains that the big brute Orion, the Hunter, once was chasing after the beautiful daughters of Atlas and Pleione. Zeus, the king of the Greek gods, heard their screams for help and transformed the maidens into white doves so that they could more easily escape Orion's lustful pursuit. They flew high into the heavens, where we can see them today as the Pleiades star cluster.
A more modern, scientific explanation for the lovely Seven Sisters star cluster is that they were, indeed, all born as siblings from the same parent cloud of interstellar gas, about 100 million years ago. There are more than 1,000 member stars in the Pleiades cluster, all lying about 410 light years away from our solar system. Leftover dust from the cluster's birth reveals itself as a blue reflection nebula around the brightest stars, especially Merope.
The Pleiades cluster stood alone as a separate constellation for many centuries. Thousands of years ago, the author of the biblical book of Job asked, "Canst thou bind the sweet influences of (the) Pleiades or loose the bands of Orion?"
Modern astronomers have included it within the boundaries of our large zodiacal constellation called Taurus, the Bull, where the tiny cluster now lies on the bull's shoulder.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Westlake’s astrophotography website at http://www.jwestlake.com.