Cetus - The Whale

Cetus can be seen from October through January. It lies south of Pisces and to the east of Aquarius. It occupies a large area in the "water" region of the fall sky. It appears as if Cetus is ready to nip at the heels of Aries, the ram, and Taurus, the bull.

History and Mythology

Cetus dates from the 2nd century AD. He is the sea monster created by Neptune that threatened Andromeda. Cetus is portrayed as a whale in modern times, but ancient mythology portrays a wide variety of monsters. One monster has a head of a greyhound and a trident-shaped tail. Some have Cetus depicted in a body resembling that of the dolphin. He lies in the area of the skies known as the Sea in ancient Babylon.

Notable Stars

Cetus is the fourth largest constellation in the sky. Alpha Ceti, has the traditional name Menkar, derived from the Arabic word meaning "nostril". It is a red giant star 200 light years away. Beta Ceti, also called Deneb Kaitos or Diphda, is located at the other end of Cetus, and its name means "tail of the sea monster". It is the brightest star in Cetus with a magnitude of 2.0.

Gamma Ceti is one of the many doubles in Cetus. It is a white and yellow binary system with magnitudes of 3.5 to 7.3, and a separation of 2.7 arcseconds.

Mira, the first variable star to be discovered, is in the "neck" of the monster. It was identified by German astronomer David Fabricius in 1596. The name Mira means "the Wonderful", as in the word miraculous. Mira changes in brightness from magnitude 2.0 to magnitude 10.1 over a period of 331 days. It is about 220 light-years away, and at its maximum, Mira is over 400 times the size of the Sun. It has a faint blue companion, but it can be seen only with a large telescope when Mira is near minimum brightness.

At magnitude 3.50, Tau Ceti is not overwhelmingly obvious. But at only 11.9 light-years away, it is one of the nearest stars. A solar-type star only slightly less luminous than our Sun, Tau Ceti was one of the two stars selected in 1960 as targets for Project Ozma, the first attempt to listen for signals from extraterrestrial intelligence. Epsilon Eridani was the other star; the project turned up nothing from either.

Another nearby star system in Cetus is the binary red dwarf system Luyten 726-8, located only 8.6 light years away. At 15th magnitude, both components are far too dim to see with the naked eye, but are occasionally known to flare by up to five times in brightness over several minutes. They carry the variable-star designations UV Ceti and BL Ceti, and are the prototypes of the class of red dwarves known as "flare stars".

Clusters, Nebulae, and Galaxies

M 77 is the only Messier object in Cetus. It is a 9th magnitude spiral galaxy with a star-like nucleus. M 77 is the prototype of the peculiar Seyfert galaxies, with an active nucleus that corresponds to the radio source Cetus A. It is about 60 million light-years from Earth.

Cetus has no prominent star clusters. It does contain the 9th magnitude planetary nebula NGC 246, nicknamed the Skull Nebula.

NGC 247 is a fairly bright, 9th-magnitude spiral galaxy in the constellation Cetus, and a member of the Sculptor Group, about 12 million light years away. IC 1613 is an irregular dwarf galaxy in Cetus, also of 9th magnitude, but is much closer - 2.8 million light years - and is a member of our Local Group.