Constellation Cetus (Sea Monster)

Cetus: IAU Constellation Map [150]


Cetus lies on the western bank of the Eridanus River, close to its source in the north. The constellation is quite large with 1231 square degrees, but contains only a few bright stars, which only form a figure after a second look. The constellation center culminates around midnight on October 15th. [9, 15]

Stars with Proper Names [154]
α Cet Menkar, Mekab, Menkab, Monkar
β Cet Diphda, Deneb Kaitos, Difda, Difda Al Thani, Rana Secunda, The "Second Frog"
γ Cet Kaffaljidhma, Al Kaff Al Jidhmah
ζ Cet Baten Kaitos
η Cet Dheneb, Deneb, Deneb Algenubi
ι Cet Deneb Kaitos Shemali, Deneb Kaitos Al Shamaliyy
λ Cet Menkar
ο Cet Mira
Data for constellation Cetus [150]
IAU NameCetus
IAU GenitiveCeti
IAU Abbr.Cet
English NameSea Monster
Opposition18 October
Season (47° N)September … December
Right Ascension23h 56m 25s … 03h 23m 47s
Declination-24° 52' 22" … +10° 30' 52"
Area1231 deg2
Neighbours (N↻)Ari, Psc, Aqr, Scl, For, Eri, Tau

Deep-Sky Object Descriptions


Constellation Cetus
Constellation Cetus: Illustration from «Uranometria» by Johann Bayer, copper engraving by Alexander Mair, 1603 [28]

Mythology and History

In Greek mythology, a huge sea monster (the whale was not seen as a meek giant in many places in the past) devastated the coasts of Ethiopia with a storm surge. To appease it, the pretty daughter Andromeda was thrown to him as a sacrifice by King Cepheus and Cassiopeia, but Perseus defeated the monster and saved her.

In addition to Cetus and Cete (sea monster, sea eel) there is also the name Pristis (sea animal, large fish) or, alternatively, Pristix and Pistrix and Canis Tritonis (dog of the sea god Triton), Balaena (whale), but also Draco (dragon) and Ursus marinus (the bear emerging from the sea). In Johann Bode's Uranographia from 1801, the constellation is called Monstrum marinum.


  • [9] «Drehbare Sternkarte SIRIUS» von H. Suter-Haug; Hallwag-Verlag, Bern
  • [15] «Hartung's Astronomical Objects for Southern Telescopes» by David Malin and David J. Frew; Melbourne University Press 1995; ISBN 0-522-84553-3
  • [28] «Uranometria omnium asterismorum continens schemata, nova methodo delineata aereis laminis expressa» Johann Bayer, Augsburg, 1603; DOI:10.3931/e-rara-309
  • [150] IAU: The Constellations, 11. Oktober 2020;
  • [154] Yale Bright Star Catalog, 15. Oktober 2020;