Cetus and Tau Ceti
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 deep. Before midnight you can find him spread out over a large expanse of the southeastern sky. A circlet of five stars forms his large head. 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 that rose majestically from the waters in the autumn and dove back in the late winter.
He is pictured in an 18th century star map 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, ending with a long, curved tale like a sea serpent.
He acted as a grotesque and scaly hitman for Poseidon, the god of the sea.
His greatest battle is a whale of a good story, a tail, er, tale, of bravery and self sacrifice. 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 Poseidon.
He 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-day 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. (Will these bad whale puns never end?) 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, delicately poached in butter or deep fried with a side of tartar sauce?”
Cetus possesses an interesting variety of astronomical objects to observe, but none is more famous than Tau Ceti, especially to science-fiction buffs.
Many stories have been written about it because the star is the closest likely candidate to have planets like our sun does. 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. Like our sun, it has reached a nice, respectable middle age. At about about 90 percent of the sun’s size but only about 45 percent of its brightness, Tau has striking similarities to our daystar.
In 1959 the astronomers of Project Ozma listened with their radio telescopes for signals from intelligent creatures like us. Scientists and explorers may look there some day for Earth-like planets if we ever send missions beyond the reaches of our solar system. If one exists, it is about .75 the distance from Tau as Earth is from our sun.
Two recent discoveries make a twin of Earth a bit less likely. Various attempts, including those of the Kepler Space Telescope, have discovered hundreds of planets orbiting other stars. However, small stars like Tau turn out to be difficult targets for such examinations.
Instead, Kepler has discovered many gas-giant planets inexplicably close to their parent stars. Such Jupiter-like planets would simply absorb Earth-like planets or cast them out of the habitable zone.
Also, in 2004 British astronomers discovered a disk of cold dust and debris around Tau. Such a disk might have formed planets like Earth in the first place. However, its presence now would make for an extraordinary number of meteor falls on any extant planet. The planet may be there, but life would find it difficult to form.
To the ancients, Cetus represented the fear of the great waters, a vast expanse of ocean filled with unknown dangers. The same turns out to be true of the vastness of space. The original discovery of planets orbiting other stars created great hope that other life might be out there. So many things can go wrong that getting a foothold might be life’s greatest challenge.
Tom Burns is the director of Perkins Observatory. He can be reached at email@example.com.