Cetus, the Sea Monster


Tom Burns - Contributing Writer



Rising low in the southern sky this month is one of the most unusual of the old constellations. The oceans represented vastness and danger to the ancient Greek people. As they looked south into the great waters of the Mediterranean, they invented a pattern of stars that represented the awe and fear that they felt.

It is the mighty Cetus, the “Whale,” rising out of the great waters. Before midnight you can find him spread out over a large expanse of the southeastern sky. His large head is formed by a circlet of five stars. He has a long, skinny body formed by a line of stars stretching to the west and ending in a rather fat tail.

Our modern identification of him as a whale is, well, kind of fishy. The Greeks couldn’t have had much experience with whales. More likely, they saw him as a sea monster who rose majestically from the waters in the autumn and dove back in the late winter.

He is pictured in an eighteenth-century star maps as a weird combination of different animals. He has an enormous head, with a large open mouth and rather formidable-looking teeth. He has claw-like front feet and a scaly body like a lizard. His body ends with a long, curved tale like a sea serpent.

He acted as a grotesque and scaly hit man for Neptune, the god of the sea. His greatest battle is a whale of a good story, a tail, er, tale, of bravery and self-sacrifice.

He is the featured villain of the Perseus/Andromeda story. Such was its importance to the ancients that every major player appears in the sky as a constellation. The tale thrives to this day in the Clash of the Titans movies. Here it is:

Cassiopeia was the Queen of Ethiopia. She is visible as a “W” of stars high in the northern sky. She spouted off that she was more beautiful than the Nereids, handmaidens to Neptune.

Neptune didn’t have much of a sense of humor about such things, so he sent Cetus to ravage the coastline of Cassiopeia’s domain. Andromeda, Cassiopeia’s daughter and a constellation visible in the eastern sky, was chained to a rock near modern Tel Aviv to act as a mid-afternoon snack for the monster. In this way, it was hoped that Neptune’s anger would be assuaged.

Andromeda faced her fate without blubbering. Luckily for her, the great hero Perseus (just to the east of Cassiopeia in the sky) came flying down on the winged horse Pegasus (just to the south of Andromeda). He dispatched Cetus, saved the innocent Andromeda, and married her.

The Ethiopians no doubt had the world’s largest fish dinner at the wedding.

One can imagine the solicitous Cassiopeia asking Perseus, “And how do you like your sea monster, dear, delicately poached in butter or deep fried with a side of tartar sauce?”

Cetus possesses an interesting variety of astronomical objects to observe.

The most famous object is the star called Mira, which roughly translates from Latin as “The Wonderful.” It was given that name in the 17th century because it was the only star known at the time to vary in brightness.

Over a period of 330 days, it pulses from naked-eye brightness to a star so dim that it takes binoculars or a telescope to see. Look for it in the center of the sea monster’s body, the second star down from the head. (More on Mira next week.)

Although it isn’t much to look at, the star called Tau Ceti, a star quite similar to our own sun. Easily visible to the naked eye, it is the bottom left star in the tail of Cetus.

Tau is one of the closest stars to our sun at about 12 light years away, or a mere 70 trillion miles. It is a middle-aged yellow star like our sun. It is about 90% of the sun’s size but only about 45% of its brightness.

In 1959 the astronomers of Project Ozma listened with their radio telescopes for signals from intelligent creatures like us. If we ever find a way to send probes to other stars, Tau will almost surely be a prime candidate because of its similarity to our sun. Five planets have been discovered or are suspected. One of them is a “Super Earth, 2 to 6 times the mass of our planet and moored in orbit within the zone that might harbor life.

To the ancients, Cetus represented the fear of the great waters, a vast expanse of ocean that was filled with unknown dangers. When we go out in the cool autumn air to look at Cetus, we should be filled with a different emotion — the glorious promise of new worlds.

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Tom Burns

Contributing Writer

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.