Alpha Ceti is a star of magnitude 2.54 in the constellation of Cetus, the Whale. It is the second-brightest star in Cetus, slightly fainter than β Cet. Alpha Ceti has the traditional name Menkar, derived from the Arabic word "manhar", meaning "nostril" (of Cetus).
Physical Properties
At a distance of 220 light years, Menkar is an old and dying star, long past the hydrogen-fusing and perhaps even past the helium-fusing stage of its evolution. Menkar is currently a three-solar-mass red giant of spectral class M1.5 IIIa, with low surface temperature of 3700 K, and a diameter 84 times the Sun's. It has a visual luminosity of about 380 suns, but most of its radiation is released in the infrared, so its total luminosity is more than 1800 times the Sun's.
Variability, Evolution, and Components
Menkar is a giant irregular variable of type Lb, fluctuating in brightness by about 6%. It will likely become highly unstable before finally shedding its outer layers and forming a planetary nebula, leaving a relatively large white dwarf remnant. Menkar is also notably deficient in carbon, having less than 20% the amount found in the Sun. More interesting, perhaps, is that it is also observed as a source of radio waves, coming from a cool stellar wind that originates from the star's surface.
This red giant star forms a very wide binocular double with the blue magnitude 5.6 star 93 Ceti, which lies 15' north. The two stars are not, however, physically related.
Cultural References
In "Star Trek II: The Wrath of Khan", Ceti Alpha V (presumably the fifth planet of Alpha Ceti) was the planet on which Khan Noonian Singh and his crew were imprisoned. The USS Menkar (AK-123) was a cargo ship commissioned by the U.S. Navy for service in World War II.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]