How stars get their names

Traditional names

Many bright-star names are Arabic, Greek, Latin or older still.

Many familiar names are Arabic. Rigel (opens in a new tab) is “the foot” of the figure the Arabs called al-jauza; Deneb (opens in a new tab) is the tail; Altair (opens in a new tab) is “the flying eagle”.

Others are Greek or Latin: Antares (opens in a new tab) means “like Mars”, Regulus (opens in a new tab) “little king”, Capella (opens in a new tab) “the she-goat”. A few go back further: Nunki (opens in a new tab) comes from a Babylonian name and is reputed to be the oldest star name still in use.

Sources for this section Jim Kaler, Rigel, STARS (University of Illinois) (opens in a new tab) · ; Ian Ridpath, Star Tales: Cygnus (opens in a new tab) · ; Ian Ridpath, Star Tales: Aquila (opens in a new tab) · ; Ian Ridpath, Star Tales: Scorpius (opens in a new tab) · ; Ian Ridpath, Star Tales: Leo (opens in a new tab) · ; Jim Kaler, Capella, STARS (University of Illinois) (opens in a new tab) · ; Ian Ridpath, Star Tales: Sagittarius (opens in a new tab)

Greek letters and catalogue numbers

Astronomers also label stars by Greek letter and constellation, and by catalogue number.

A Greek letter is combined with the Latin possessive of the constellation's name. The IAU's example (opens in a new tab) is Hamal, the brightest star in Aries, also called Alpha Arietis, “the alpha of Aries”.

The letters do not always follow brightness: Rigel, beta Orionis, usually outshines Betelgeuse, alpha, and Jim Kaler (opens in a new tab) suggests either a brighter Betelgeuse at the time or Bayer going by position. In Sagittarius, Ptolemy's misjudged magnitudes (opens in a new tab) left alpha only the 15th brightest star.

Catalogues add numbers. This site's charts use the Bright Star Catalogue (opens in a new tab)'s HR numbers, and the IAU notes (opens in a new tab) that deep-sky objects are named by catalogue, such as NGC 6720 or IC 165.

Sources for this section International Astronomical Union, The Constellations (opens in a new tab) · ; Jim Kaler, Rigel, STARS (University of Illinois) (opens in a new tab) · ; Ian Ridpath, Star Tales: Sagittarius (opens in a new tab) · ; Bright Star Catalogue, 5th Revised Ed. (Hoffleit & Warren 1991), as computed by this site's star engine (opens in a new tab) · ; International Astronomical Union, Astronomy FAQs (opens in a new tab)

Who decides, and the names you cannot buy

The IAU standardises star names, drawing on many traditions; nobody can sell you one.

The IAU's Working Group on Star Names (opens in a new tab) was set up to standardise star names for research. Since 2015 it has fixed the spellings of commonly used names, and it names stars bright enough to see from historical and Indigenous traditions of all kinds, if appropriate and allowed by the culture of origin, recruiting members from anthropology, ethnology, cultural studies and history.

The approved names are listed in the IAU Catalog of Star Names (opens in a new tab); this site checks every name on its charts against that file.

The IAU dissociates itself entirely (opens in a new tab) from companies selling star names: it offers no star-naming service, and there is no official way to buy one.

Keep in mind Chinese, Indigenous and other sky traditions have their own names and their own star groupings, which are not simply nicknames for the 88 IAU figures. Historical beliefs keeps them with their traditions.

Sources for this section IAU Division C Working Group on Star Names (opens in a new tab) · ; IAU Working Group on Star Names, IAU Catalog of Star Names (IAU-CSN) (opens in a new tab) · ; International Astronomical Union, Astronomy FAQs (opens in a new tab)