Jimmy Westlake: Exploring the constellation Perseus
August 11, 2015
With the annual Perseid meteor shower rising to its peak activity this week, it's a good time to introduce you to the constellation that gives this delightful shower of shooting stars its name.
Meteor showers are named for the constellation from which their meteors appear to stream, in this case, Perseus, the Hero.
Hollywood has created some scary monsters for us over the years, but Hollywood has nothing on ancient Greece. Some of the monsters passed down to us through Greek mythology are as terrifying as anything ever conjured up by the human imagination.
To me, the most chilling monster of them all is the Gorgon sister Medusa. At one time, Medusa was a beautiful young woman with long, flowing hair. Many young suitors sought to win her hand in marriage.
One day, while Medusa prayed in the temple of Athena, Poseidon, the Greek god of the sea, entered the temple and ravished her. Athena was furious that her temple would be so violated. As punishment, she transformed the lovely Medusa into a hideous monster, changing her beautiful hair into a writhing tangle of hissing snakes and proclaiming that any man who gazed into her eyes would be turned into solid stone.
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Medusa met her death at the hands of the Greek hero Perseus, who was dispatched by the king to slay her and bring back the Gorgon's head. Armed with a magic sword, winged sandals and a mirror-like shield, Perseus crept up on the slumbering Medusa in her lair.
While watching her harmless reflection in his shiny shield, he severed her ugly head and stowed it in a leather pouch. Perseus used Medusa's head as an effective weapon in several epic battles, turning his foes into stone.
The hero Perseus is immortalized in our late summer sky as a magnificent constellation. He is poised there, in his winged sandals, victoriously holding his sword in one hand and the severed head of Medusa in the other.
His pointy helmet first protrudes above our northeast horizon around 10 p.m. in mid-August and, by midnight, Perseus is in full view. Look for him just beneath the very familiar "W" shaped pattern of Cassiopeia, the Queen.
The constellation of Perseus contains many interesting celestial objects to explore. First and foremost is the bright star that marks the eye of Medusa, a most remarkable star named Algol.
Every three days, the star Algol fades to one-third of its normal brightness for two hours and then returns to its original luster. It's as if Medusa is winking her evil eye at us.
Algol's periodic winking horrified ancient sky watchers but is no longer a mystery. Algol is actually a pair of stars, almost in contact as they whirl around each other. When the fainter star eclipses the brighter star, Algol dims its light for a few hours. Algol was the first eclipsing binary star discovered and is, without a doubt, the most famous.
Just above Perseus' head, toward Cassiopeia, you can spot a prominent fuzzy smudge with the unaided eye. Aim a pair of ordinary binoculars at this smudge, and you will discover one of the most spectacular deep sky objects visible from Earth — the famous Double Cluster.
These twin star clusters are formally known as h and χ Persei and lie an incredible 7,500 light years from Earth. h and χ Persei are sparkly siblings that likely formed from the same interstellar gas cloud some 12 million years ago and, although they appear close together in our sky, are really hundreds of light years apart.
While you are in the Perseus area, check out a couple of other celestial wonders — the Great Andromeda Galaxy (M31) and the Seven Sisters star cluster (M45).
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.