Cetus, the Greek mythological sea monster, is a large southern constellation on the celestial equator, and one of the 48 constellations cataloged by 2nd century astronomer Ptolemy. It is accompanied by other water constellations – Pisces, Aquarius and Eridanus. Its head is nestled among three zodiacal constellations: Taurus, Aries and Pisces. Its body is south (below) Pisces, and is flanked by Aquarius and Eridanus. Cetus’ close proximity to the ecliptic means that the Moon, planets and asteroids occasionally pass through this constellation. Cetus is placed highest in the sky at nightfall in December.
Cetus is home to one Messier object, M77, a striking face-on spiral galaxy. Among Cetus’ stars is an unusual variable star, the disappearing one, or Mira (Omicron Ceti). This star’s high variability from 3rd magnitude to 10th magnitude means that it disappears from view when it dips below 5th or 6th magnitude. Cetus’ brightest star Menkar (Alpha Ceti) marks the sea monster’s nose.
© James R. Johnson, 2014.