Cetus is a constellation in the northern sky. Its name refers to Cetus, a sea monster in Greek mythology, although it is often called 'the whale' today. Cetus is located in the region of the sky known as the Water, along with other watery constellations such as Aquarius, Pisces, and Eridanus.

Notable features

Ecliptic

Although Cetus is not considered part of the zodiac, the ecliptic passes close to its constellation boundary, and thus the planets may be seen in Cetus for brief periods of time. This is even more true of asteroids, since their orbits usually have a greater inclination to the ecliptic than planets; for example, the asteroid 4 Vesta was discovered in this constellation in 1807.

Stars

This constellation's most notable star is Mira (or ό Ceti), the first variable star to be discovered. Over a period of 331.65 days it can reach a maximum magnitude as high as 2.0^m, one of the brightest in the sky and easily visible to the unaided eye, then drop to 10.1^m and back again. Its discovery in 1596 by David Fabricius further dented the supposed unchangeability of the heavens and lent support to the Copernican revolution.

Other stars in the constellation include α Ceti (Menkar); β Ceti (Deneb Kaitos), brightest in the constellation; and τ Ceti, the 17th closest star to Earth.

Deep sky objects

Cetus lies far from the galactic plane, so many distant galaxies are visible, unobscured by dust from the Milky Way. Of these, the brightest is Messier 77 (NGC 1068), a 9th magnitude spiral galaxy near δ Ceti. Recently, the galactic cluster JKCS 041 was confirmed to be the most distant cluster of galaxies yet discovered.