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Cetus (/ˈstəs/) is a constellation. 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 that contains other water-related constellations such as Aquarius, Pisces, and Eridanus.

Pronunciation/ˈstəs/, genitive /ˈst/
Symbolismthe Whale, Shark, or Sea Monster
Right ascension 00h 26m 22.2486s– 03h 23m 47.1487s[1]
Area1231 sq. deg. (4th)
Main stars14
Stars with planets23
Stars brighter than 3.00m2
Stars within 10.00 pc (32.62 ly)9
Brightest starβ Cet (Deneb Kaitos)† (2.04m)
Messier objects1
Meteor showersOctober Cetids
Eta Cetids
Omicron Cetids
Visible at latitudes between +70° and −90°.
Best visible at 21:00 (9 p.m.) during the month of November.
Note:Mira (ο Cet) is magnitude 2.0 at its brightest.



The constellation Cetus as it can be seen by the naked eye.


Although Cetus is not generally considered part of the zodiac, the ecliptic passes less than a quarter of a degree from its constellation boundary, and thus the moon, planets, and even part of the sun may be in Cetus for brief periods of time. This is all the more true of asteroids since their orbits usually have a greater inclination to the ecliptic than the moon and planets.

As seen from Mars, the ecliptic passes into Cetus, with the sun appearing in Cetus for around six days shortly after the northern summer solstice. Mars's orbit is tilted by 1.85° with respect to Earth's.


Mira ("the Wonderful"), designated Omicron Ceti, was the first variable star to be discovered and the prototype of its class. Over a period of 332 days, it reaches a maximum apparent magnitude of 3 - visible to the naked eye - and dips to a minimum magnitude of 10, invisible to the unaided eye. Its seeming appearance and disappearance gave it its common name, which means "the amazing one". Mira pulsates with a minimum size of 400 solar diameters and a maximum size of 500 solar diameters. 420 light-years from Earth, it was discovered by David Fabricius in 1596.[2]

α Ceti, traditionally called Menkar ("the nose"), is a red-hued giant star of magnitude 2.5, 220 light-years from Earth. It is a wide double star; the secondary is 93 Ceti, a blue-white hued star of magnitude 5.6, 440 light-years away. β Ceti, also called Deneb Kaitos and Diphda is the brightest star in Cetus. It is an orange-hued giant star of magnitude 2.0, 96 light-years from Earth. The traditional name "Deneb Kaitos" means "the whale's tail". γ Ceti, Kaffaljidhma ("head of the whale") is a very close double star. The primary is a yellow-hued star of magnitude 3.5, 82 light-years from Earth, and the secondary is a blue-hued star of magnitude 6.6.[2] Tau Ceti is noted for being the nearest Sun-like star at a distance of 11.9 light-years. It is a yellow-hued main-sequence star of magnitude 3.5.

AA Ceti is a triple star system; the brightest member has a magnitude of 6.2. The primary and secondary are separated by 8.4 arcseconds at an angle of 304 degrees. The tertiary is not visible in telescopes. AA Ceti is an eclipsing variable star; the tertiary star passes in front of the primary and causes the system's apparent magnitude to decrease by 0.5 magnitudes.[3] UV Ceti is an unusual binary variable star. 8.7 light-years from Earth, the system consists of two red dwarfs. both of magnitude 13. One of the stars is a flare star, which are prone to sudden, random outbursts that last several minutes; these increase the pair's apparent brightness significantly - as high as magnitude 7.[2]

Deep-sky objectsEdit

Messier 77 spiral galaxy by HST.[4]
Cetus by Willem Blaeu, 1602.

Cetus lies far from the galactic plane, so that 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 Delta Ceti. It appears face-on and has a clearly visible nucleus of magnitude 10. About 50 million light-years from Earth, M77 is also a Seyfert galaxy and thus a bright object in the radio spectrum.[2] Recently, the galactic cluster JKCS 041 was confirmed to be the most distant cluster of galaxies yet discovered.[5]

The massive cD galaxy Holmberg 15A is also found in Cetus. As is spiral galaxy NGC 1042 and ultra-diffuse galaxy NGC 1052-DF2.

IC 1613 (Caldwell 51) is an irregular dwarf galaxy near the star 26 Ceti and is a member of the Local Group.

NGC 246 (Caldwell 56), also called the Cetus Ring, is a planetary nebula with a magnitude of 8.0, 1600 light-years from Earth. Among some amateur astronomers, NGC 246 has garnered the nickname "Pac-Man Nebula" because of the arrangement of its central stars and the surrounding star field.[6]

History and mythologyEdit

Cetus dominates this card from Urania's Mirror (1825).

Cetus may have originally been associated with a whale, which would have had mythic status amongst Mesopotamian cultures. It is often now called the Whale, though it is most strongly associated with Cetus the sea-monster, who was slain by Perseus as he saved the princess Andromeda from Poseidon's wrath. Cetus is located in a region of the sky called "The Sea" because many water-associated constellations are placed there, including Eridanus, Pisces, Piscis Austrinus, Capricornus, and Aquarius.[7]

Cetus has been depicted in many ways throughout its history. In the 17th century, Cetus was depicted as a "dragon fish" by Johann Bayer. Both Willem Blaeu and Andreas Cellarius depicted Cetus as a whale-like creature in the same century. However, Cetus has also been variously depicted with animal heads attached to a piscine body.[7]

In global astronomyEdit

In Chinese astronomy, the stars of Cetus are found among two areas: the Black Tortoise of the North (北方玄武, Běi Fāng Xuán Wǔ) and the White Tiger of the West (西方白虎, Xī Fāng Bái Hǔ).

The Brazilian Tukano and Kobeua people used the stars of Cetus to create a jaguar, representing the god of hurricanes and other violent storms. Lambda, Mu, Xi, Nu, Gamma, and Alpha Ceti represented its head; Omicron, Zeta, and Chi Ceti represented its body; Eta Eri, Tau Cet, and Upsilon Cet marked its legs and feet; and Theta, Eta, and Beta Ceti delineated its tail.[7]

In Hawaii, the constellation was called Na Kuhi, and Mira (Omicron Ceti) may have been called Kane.[8]


USS Cetus (AK-77) was a United States Navy Crater class cargo ship named after the constellation. "Cetus" is the title of a ragtime piano composition by Tom Brier on the album "Constellations".

See alsoEdit


  1. ^ a b "Cetus, constellation boundary". The Constellations. International Astronomical Union. Retrieved 15 February 2014.
  2. ^ a b c d Ridpath & Tirion 2001, pp. 114-116.
  3. ^ Levy 2005, p. 67.
  4. ^ "Hubble observes the hidden depths of Messier 77". ESA/Hubble. Retrieved 4 April 2013.
  5. ^ "Scientists identify new". Metro. 23 October 2009.
  6. ^ Levy 2005, p. 129.
  7. ^ a b c Staal 1988, pp. 33–35
  8. ^ Makemson 1941, p. 281.


External linksEdit