Jimmy Westlake: Cetus: A whale of a constellation
November 9, 2008
Steamboat Springs — Wedged in between the bright star Fomalhaut (pronounced fo-ma-lo) to the south and the glittering Pleiades star cluster to the east is the huge, lumbering constellation of Cetus, the Whale. It ranks fourth in overall size among the 88 official constellations; only Hydra, Ursa Major and Virgo cover more area of the sky. Yet, despite its large size, Cetus claims no star brighter than second magnitude and has only one of those.
Since the earliest times, Cetus has been identified with the mythological beast created by Poseidon’s anger at Queen Cassiopeia for daring to boast that her daughter Andromeda was more beautiful than the daughters of Poseidon. The only way to stop the monster’s killing spree was to sacrifice the lovely Andromeda to him. As she awaited her fate, chained to the rocks along the shore, Cetus was transformed into a mountain of stone when the hero Perseus suddenly appeared and dangled the severed head of the Medusa before him. This mythological sea monster bore little resemblance to a whale, yet, seventeenth century astronomers chose to portray the image of a whale among these stars and the image seems to have stuck. There are even references that identify our Cetus the Whale with the giant cetacean that swallowed Jonah in the Old Testament story.
During early to mid-November, Cetus has completely risen above our southeastern mountains by 8 p.m. Its brightest star is Deneb Kaitos, the Whale’s Tail, visible not far to the east of the brighter star Fomalhaut. From there, the Whale extends 40 degrees to the north and east to the star Menkar, the Nose. Menkar and four other stars form a distinctive pentagon shape that represents the head of the sea monster.
There are two other very interesting stars within the constellation of Cetus worth mentioning. First is the star Tau Ceti, one of the closest sun-like stars outside of our solar system. Because it is nearly the same size, temperature and color of our sun, it makes a perfect target for astronomers searching for habitable planets such as Earth and, at a distance of 11.9 light years, might one day become home to a space colony as we leave our cradle behind. So far, no planets have been identified orbiting Tau Ceti, but a large ring of rocky debris, not unlike our own asteroid belt, has been detected. Tau Ceti has figured heavily in many science fiction stories in the past and will no doubt continue to capture the imagination of stargazers and dreamers everywhere.
The second star of note within the borders of Cetus isn’t even visible to the naked eye except for a few weeks out of each year. It is the star Omicron Ceti, also known as Mira, the wonderful star. Mira is a long period variable star that first caught astronomers’ attention many centuries ago. It varies between magnitudes 10 (invisible even in binoculars) and 3 or 2 in a period of about 332 days.
When near maximum light, as it will be this coming January, Mira can sometimes rival Deneb Kaitos as Cetus’ brightest star, though it typically maxes out slightly fainter. Mira is on the rise now, so keep an eye out for this amazing variable star as it once again becomes visible to the naked eye this fall.