Stargazing: Perseus, blah, blah, blah


By Tom Burns - Stargazing



As I approach my retirement in eight months or so from Perkins Observatory, my mind turns to the quarter century that I have worked there showing people what their universe looks like. Mostly, I remember each of the thousands of public programs I have done with joy. However, sometimes, the experience is downright humbling.

An experience of the latter variety happened about five years ago around this time of year. As I gave the usual talk before the usual telescope observing session, I paused dramatically to begin my inspirational “big finish.” A six-month-old babe in arms named Gabriella began to speak. “Blah, blah, blah, blah, blah” she babbled cheerfully. The audience erupted with laughter, and so did I.

Yes, that’s right. You can talk about the wonders of the universe to exhaustion, but nothing beats the direct experience of its beauty. On the other hand, looking at a bunch of specks in the sky can be a pretty boring and unrewarding experience if you don’t have a little scientific and cultural context.

The constellation Perseus is a case in point. You’ll find it — or him, if you prefer — high in the northeastern sky around 8 PM. Look especially for Mirphak, the constellation’s brightest star, which forms the hero’s chest. To the left and slightly up is Algol, the winking eye of the Gorgon Medusa.

Algol winks because it is a variable star, i.e., a class of stars that vary in their brightness. Stars brighten and dim for various reasons, but Algol changes because it is, in fact, not one star at all. In this three-star system, one of the unseen, dimmer stars orbits the bright one we see. As the dimmer companion passes in front of the bright star, the brighter one gets dimmer. Thus, every 2.85 days, the brighter star dims for about 10 hours — a slow-motion wink.

Italian astronomer Geminiano Montanari was first to record Algol’s variability in 1667, but the ancients must have noticed the wink. That’s why they put the starry version of the hideous Gorgon’s head in Perseus’s outstretched hand.

Why is Perseus holding an eyeball? Read on, gentle stargazers. Yes, that’s right. More “blah, blah, blah” follows.

King Acrisius should have been a happy man. He ruled the bountiful land of Argos.

His daughter Danae charmed everyone with her intelligence and beauty. But Acrisius was driven nearly insane by a prophecy that foretold his death by a son, yet unborn, of his innocent daughter.

To prevent Danae from marrying, the king locked her in a tower and vowed that the all-to-human eyes of potential suitors would never again gaze upon her. The unlucky king didn’t figure on immortal eyes, however. Zeus, king of all the gods, easily saw through the tower walls. ”Wowza,” he said in ancient Greek, turned himself into a shower of gold coins, and rained himself down on Danae’s lap through a skylight. Nine months later, Perseus was born.

In anger and fear, Acrisius set his daughter and grandson adrift into the sea in a wooden chest. This was, of course, very bad parenting, but Danae’s desperate explanations must have sounded false. “It was the coins, Dad, the COINS, honest.”

The chest came to ground at Seriphos, an island ruled by the vicious Polydectes. Perseus grew to young manhood. All the while, Polydectes kept a lustful eye on Danae.

After his wife died, Polydectes asked the comely woman to marry him. She said no. Polydectes imprisoned her in his palace for immoral purposes. Polydectes knew that he had to rid himself of Perseus, so he gave him an impossible task — to bring home the head of Medusa, the Gorgon.

The Gorgons were three sisters with live snakes for hair and a single eye and tooth, which they had to share among themselves. Medusa was so ugly that a single glance at her face turned the unfortunate viewer to stone.

Tough job, but Perseus undertook it because he hoped that he could eventually find a way of liberating his mother. Using only the reflection of Medusa in his shield, he lopped off the Gorgon’s head and put it in a sack.

Perseus had many adventures on the way home. Among other things, he rescued his future wife Andromeda from the clutches of the sea monster Cetus, but that’s another constellation story.

Polydectes was surprised to see Perseus return. He figured that the hero would not survive his encounter with the Gorgon. He was even more surprised, but only for a split second, when Perseus pulled Medusa’s head out of the sack and turned him into a statue.

After many great adventures, Perseus returned with his mother and wife to Argos, the land of his birth. His grandfather, Acrisius, had been driven from power during their absence, and Perseus became king.

Despite his high status, he was a man of the people, often participating in their athletic competitions. At one such contest, he threw a discus with such force that he accidentally killed someone in the crowd. It was thus that the prophecy that began this tale came true. The unfortunate bystander was none other than Acrisius.

As for Perseus, he lives now among the stars, the head of Medusa with its single eye still clutched in his hand. From his lofty perch, he speaks to us from our ancient, mythological past, when good deeds, long suffering, and a sympathetic heart never went unrewarded.

Now go out and look at the constellation Perseus. Doesn’t a little “blah, blah, blah” enhance the experience?

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By Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.