Jimmy Westlake: Explore the Pleiades and Comet Lovejoy this week
January 19, 2015
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, with a tiny little bowl and a tiny little handle, its real name is the Pleiades star cluster. It is the 45th object listed in Charles Messier's famous catalog of comet look-alikes (M45) and is popularly known as the Seven Sisters. In Japan, it 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 the six brightest stars in the Pleiades 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 eight, nine or even 10 stars with their 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 seven brightest stars are named for the sisters; the other two represent the parents.
In order of decreasing brightness, the seven brightest 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 will reveal the entire family very clearly, and many dozens more stars to boot.
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Greek mythology explains that the big brute Orion, the Hunter, was stalking 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 are still seen today as our Pleiades star cluster, just out of the reach of the nearby starry figure of Orion. The three stars of Orion's Belt point upward, like an arrow, toward the Seven Sisters.
A more modern, scientific explanation for the lovely Seven Sisters star cluster is that they were, indeed, all born as siblings from the same cloud of interstellar gas about 100-million years ago. There are over 1,000 member stars in the Pleiades cluster, all lying about 410 light years away from our solar system. This means that, when you look at the Pleiades, you are looking back in time and seeing the cluster as it was 410 years ago.
The Pleiades cluster stood alone as its own constellation for many centuries. Thousands of years ago, the author of the biblical book of Job asked, "Can you bind the chains of the Pleiades or loosen the belt of Orion?"
Modern astronomers have included the cluster within the boundaries of our large constellation called Taurus, the Bull. The twinkly cluster now resides on the bull's shoulder.
This week, while exploring the Pleiades cluster with your binoculars, you can also spot the icy little interloper Comet Lovejoy Q2. It is faintly visible to the unaided eye, about a fist width at arm's length to the right (west) of the Pleiades.
Binoculars will reveal the fuzzy green head and its eastward-pointing tail, at least until the moon moves back into the evening sky late this week.
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 Jimmy's astrophotography website at http://www.jwestlake.com.