Constellations: Overview | Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Boötes | Caelum
Camelopardalis | Cancer | Canes Venatici | Canis Major | Canis Minor | Capricornus | Carina | Cassiopeia | Centaurus
Cepheus | Cetus | Chamæleon | Circinus | Columba | Coma Berenices | Corona Australis | Corona Borealis | Corvus
Crater | Crux | Cygnus | Delphinus | Dorado | Draco | Equuleus | Eridanus | Fornax | Gemini | Grus | Hercules | Horologium
Hydra | Hydrus | Indus | Lacerta | Leo | Leo Minor | Lepus | Libra | Lupus | Lynx | Lyra | Mensa | Microscopium | Monoceros
Musca | Norma | Octans | Ophiuchus | Orion | Pavo | Pegasus | Perseus | Phoenix | Pictor | Pisces | Piscis Austrinus
Puppis | Pyxis | Reticulum | Sagitta | Sagittarius | Scorpius | Sculptor | Scutum | Serpens | Sextans | Taurus
Telescopium | Triangulum | Triangulum Australe | Tucana | Ursa Major | Ursa Minor | Vela | Virgo | Volans | Vulpecula

Have you gazed out on the ocean
Seen the breaching of a whale?
Have you watched the dolphins frolic in the foam?
Have you heard the song the humpback hears
Five hundred miles away?
Telling tales of ancient history of passages and home.
– 'I Want To Live' – John Denver

The Constellation Cetus

Cetus the whale (or 'sea monster') is a huge southern constellation; at 1,231 square degrees, it's the 4th-largest overall. Cetus is in the area of the sky known as 'the Sea' alongside other 'water' constellations. Bordering Cetus is Eridanus 'the river'; above it is Taurus, Aries and Pisces; and the other side is Aquarius. Beneath Cetus are Sculptor and Fornax.

History

The Roman historian Pliny claimed to have seen the 40' skeleton of a strange marine creature when it was brought to Rome. It was described as front part dog with a fish bottom half, a sort of 'canineplacoderm', or just a really ugly mermaid. This portmanteau is exactly how Cetus is depicted in John Flamsteed's Atlas Coelestis.

Mythology

The vain queen Cassiopeia, wife of King Cepheus of Æthiopia, offended the god of the oceans, Poseidon, when she boasted that her beauty was greater than that of the sea nymphs, the Nereids, who were his handmaidens. Angry Poseidon sent storms to ravage the coast of their kingdom as punishment for the queen's vanity. To bring an end to the suffering, King Cepheus went to the Oracle for advice and was told to sacrifice his daughter Andromeda to the sea monster Cetus in order to placate Poseidon.

Andromeda was duly chained to the rocks on the coast² for the sea monster to devour. She was saved at the last moment by the hero Perseus, riding in on Pegasus, his winged horse. Perseus turned Cetus to stone by forcing it to look at the head of the gorgon Medusa, who Perseus had recently slain. The sea monster was immortalised as a constellation by the great god Zeus.

Stars

The scientific star names are simple to understand (if you know your Greek alphabet). For example: 'Alpha Ceti' means that it is the brightest star in the constellation Cetus. The next brightest is designated 'beta', and so on. This is known as the 'Bayer designation'. Some stars have proper names as well; for example, alpha Ceti is Menkar. Others are known by their catalogue number.

The stars of Cetus don't quite follow the nomenclature rule; discounting variable star omicron Ceti, the brightest star of the constellation is beta Ceti, Deneb Kaitos, while several others are out of order.

The first variable star to be discovered was omicron Ceti, commonly named Mira (Latin meaning 'the amazing one'). It fluctuates between magnitude +10 and +1, making it one of the brightest periodic variables. Mira's strange behaviour pattern, including disappearing from view for part of its cycle, led astronomers to mistakenly assume it was a nova (exploding star). At the time of its scientific discovery in 1596, most people had a geocentric world-view (in which the Earth is at the centre of the universe and every other heavenly body revolves around it). To voice a different theory was considered heresy and many people died for their beliefs. The study of omicron Ceti added to the weight of evidence which eventually led towards the scientifically accepted heliocentrism.

Other interesting stars are: Tau Ceti which has a debris disc and is very close by at just 12 light years³ distant; Phi Ceti is a quadruple star system; another multiple is epsilon Ceti.

New General Catalogue (NGC)

The NGC was compiled by John Louis Emil Dreyer (the director of the Armagh Observatory from 1882 to 1916). The NGC objects in Cetus are a planetary nebula and two galaxies, one of which is included in the famous catalogue of Charles Messier.

Extrasolar Planets in Cetus

There have been several extrasolar planetary systems found in the constellation Cetus; the first was discovered in 2000; one star has three orbiting planets. Figures given in the table below are the length of the planet's orbital period around its parent star, which we know of as a year. The mass of the extrasolar planet is compared to that of Jupiter, our Solar System's largest planet, known by astronomers as the 'Jovian scale'.

Whales in Modern Culture

• A sperm whale, created by the Infinite Improbability Drive, had a brief appearance in the Hitchhiker's Guide to the Galaxy by Douglas Adams.
• According to the King James version of The Bible, Jonah was swallowed by a whale, but vomited back out again after God spared Jonah's life.
• When NASA discovered that sperm whale oil did not freeze in outer space, they used it as a lubricant in the vehicles of their space programme, including the ROV (Remotely Operated Vehicle) for expeditions to the Moon and Mars, where the surface temperature is extremely cold indeed. The discovery was so significant that Sir Patrick Moore devoted a whole programme of The Sky At Night to talk about the implications, and invited marine biologists and cetacean experts to join the discussion.
• The novel Moby-Dick was written in 1851 by Herman Melville. The story is about a ship's captain who becomes obsessed with hunting a whale, Moby-Dick, who the captain blames for the loss of his leg on a previous whaling expedition. The battle between the hunter and the hunted is to the death, but the tale itself has come to symbolise the fight within, and the choice we all have, when to let go.
• A town on the southern coast of France is named Sète and a whale appears as a visual pun in the town's coat of arms. The name derives from a fairly ancient way of using 'set' to mean 'mountain', but the name was spelled 'Cette' after the 17th Century - hence the whale connection. The spelling was changed after 1936, but the whale remains on the coat of arms.

Cetus in Science Fiction

In Star Trek TOS, villain Khan Noonian Singh and his followers were imprisoned on the 5th planet from Alpha Ceti, which was named as Alpha Ceti V. Pirates hid on a planet orbiting Mira (omicron Ceti) in A Relic Of The Empire by Larry Niven. There's a wormhole connecting Earth and UV Ceti in Timemaster by Robert Lull Forward (1932 - 2002). To list the references to Tau Ceti in the science fiction genre would require an Entry all on its own, so suffice to say it's a popular star!

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¹ Current IAU guidelines use a plus sign (+) for northern constellations and a minus sign (−) for southern ones.
² This scene inspired artists such as Paul Gustav Doré.
³ A light year is the distance light travels in one year, roughly 5.88 trillion miles or 9.46 trillion km.