Constellation, Sea Monster
Cetus
The sea monster sent to devour Andromeda, sometimes called the whale. It holds Mira, the wonderful star, the first star found to rise and fall in brightness in a repeating cycle.
From New York on October 13, 2026, the centre of Cetus rises at 7:37 PM, is highest at 1:14 AM (42° above the horizon in the S) and sets at 6:50 AM.
In the 3D sky
The sky over New York turned towards Cetus. Drag to look around.
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Evening visibility over the year
Height of the constellation’s centre above the horizon at 10 pm local time on the 15th of each month, from New York. Above about 30° it is well placed.
Name and history
In Greek myth, Cetus was the monster that the sea god Poseidon sent to ravage the coast of Ethiopia after Queen Cassiopeia boasted that she was more beautiful than the sea nymphs. Princess Andromeda was chained to a rock as its victim, and the hero Perseus killed it to save her. The Latin word cetus means whale, but the Greek ketos meant any sea monster. In most pictures it is a strange beast with gaping jaws, the forefeet of a land animal and a coiled, scaly tail. Albrecht Dürer drew it in 1515 as a large fish with a forked tail.
Menkar comes from an Arabic word for the nostrils. Diphda comes from the Arabic for the second of a pair of frogs, the first being Fomalhaut. Its old name Deneb Kaitos means the sea monster’s tail. In 1596 the German astronomer David Fabricius recorded a star here that later faded from sight. Its regular cycle was recognised in 1638, and in 1662 Johannes Hevelius named it Mira, the wonderful.
Sources: Ian Ridpath, Star Tales: Cetus
Brightest stars
| Star | Designation | Magnitude | Distance |
|---|---|---|---|
| Diphda | β Cet | 2.04 | 96 light-years |
| Menkar | α Cet | 2.54 | 249 light-years |
| η Cet | η Cet | 3.46 | 124 light-years |
| Kaffaljidhma | γ Cet | 3.47 | 80 light-years |
| τ Cet | τ Cet | 3.49 | 12 light-years |
| ι Cet | ι Cet | 3.56 | 275 light-years |
| θ Cet | θ Cet | 3.60 | 114 light-years |
| Baten Kaitos | ζ Cet | 3.74 | 235 light-years |
| υ Cet | υ Cet | 3.99 | 293 light-years |
| δ Cet | δ Cet | 4.08 | 650 light-years |
Facts
| Area | about 1,231 square degrees (4 of 88) |
|---|---|
| IAU abbreviation | Cet |
| Sky | Near the celestial equator, visible from both hemispheres |
| Origin | Listed in Ptolemy’s Almagest, about AD 150, from older Greek tradition |
| Stars brighter than magnitude 5 | 30 |
| Centre (J2000) | 1.8 h, -8° |
Deep-sky objects
Galaxies, clusters and nebulae brighter than magnitude 9, from the OpenNGC catalogue. Most need binoculars or a telescope and a dark sky.
No deep-sky object brighter than magnitude 9.
Boundaries: International Astronomical Union, via Astronomy Engine. Areas are computed from the boundaries by sampling (within about one percent). Names and lines: Stellarium. Stars: HYG Database. Deep-sky objects: OpenNGC. Calculated with Astronomy Engine, an open-source library verified against the US Naval Observatory and NASA JPL. Data sources
How to use this page
Choose your place and a night at the top. The answer and the 3D view show where the constellation is, when it is highest and whether it rises at all from where you are. The chart shows its stars and lines, and the tables list its brightest stars and the deep-sky objects inside it.
Frequently asked questions
When is a constellation best seen?
When it is highest in a dark sky, which the page gives for the night you pick. Each constellation is best placed in a particular season, because the stars rise about four minutes earlier every night.
Why can I not see a constellation from my place?
Constellations far south of the celestial equator never rise from northern places, and those far north never rise from southern ones. The page says when this is the case.
What are the constellation boundaries?
The International Astronomical Union divides the sky into 88 areas with official boundaries. The stick figures are only a drawing aid, the boundaries say which constellation a point in the sky belongs to.
Related guides
- How to learn the constellationsStart with one bright pattern you cannot miss, use it as a signpost to its neighbours, and come back a month later: the sky will have turned, and you will know a little more of it.
- Altitude and azimuth: finding things in the skyTwo angles tell you exactly where to look: which direction, and how high.
- Light pollution and dark skies: the Bortle scaleFrom a city centre you can count a few dozen stars. From a truly dark site you can count a few thousand, with the Milky Way bright enough to cast a shadow. The Bortle scale puts a number on the difference.
- Binoculars for stargazing: what to buy and what to look atA pair of 7x50 or 10x50 binoculars shows the craters of the Moon, the moons of Jupiter, dozens of star clusters and the Andromeda Galaxy, for a fraction of the cost of a telescope.