Who Named the Stars? Arabic Words, Greek Letters and a Modern Committee

Greek astronomical work, above all the catalogue compiled by Ptolemy in the second century, was translated into Arabic from the ninth century onwards and studied, extended and corrected by astronomers across the Islamic world for several hundred years. Those texts were then translated into Latin in Spain and Sicily from the twelfth century, and European astronomy inherited both the content and the vocabulary. Many star names therefore reach English through Arabic, and a number are descriptive phrases identifying the star's position within a figure, so several translate as the shoulder, the tail or the foot of whichever constellation animal they belong to. Some names were garbled in transmission, and a few are corruptions of corruptions whose original meaning has been reconstructed only with effort.

Several naming schemes operate simultaneously and each serves a purpose:

• •Proper names, mostly Arabic with some Greek and Latin, used for a few hundred bright stars
• •Greek letters with the constellation name, assigned roughly by brightness within each constellation
• •Latin letters and numbers, extending the same scheme to fainter stars
• •Catalogue designations, which are numbers in a specific published survey
• •Variable star designations, which follow their own lettering convention
• •Coordinates, which identify anything at all and are what professionals mostly use

Naming was inconsistent for centuries, with spellings varying between atlases and with the same star carrying different names in different sources. The International Astronomical Union, founded in 1919, is the body recognised for naming astronomical objects, and it established a working group on star names in 2016 which has published a catalogue of approved names with fixed spellings, resolving duplicates and ambiguities. The same organisation names planets, moons, and surface features, with conventions specifying the category of name appropriate to each kind of object. Names of newly discovered objects follow those conventions, and public naming campaigns are run occasionally under the organisation's supervision, with the results carrying official standing.

Star names sit within constellations and those boundaries have their own history. Figures in the sky were traditional and their outlines varied between atlases, with stars near a boundary assigned differently by different mapmakers and with some constellations invented by individuals to flatter patrons and quietly dropped later. That ambiguity mattered once catalogues needed to reference stars unambiguously, and the International Astronomical Union settled it in 1930 by dividing the entire sky into eighty eight regions with boundaries following lines of constant coordinate, so every point in the sky now belongs to exactly one constellation whether or not any stars there form a figure. The boundaries were fixed to the coordinate system of a particular date, and because the earth's axis shifts slowly, they have since drifted slightly askew.

Commercial services offering to name a star after somebody sell a certificate and an entry in a private register, and that is the whole of what is provided. No astronomical body recognises those names, they appear in no catalogue anyone uses, and the same star may be sold repeatedly by different companies. Consumer protection authorities in several countries have acted against such businesses over how the offer is described. The astronomical union states its position plainly on its own website. The transaction is not fraudulent where the limitations are disclosed, and it is frequently bought by people who believe they are obtaining something official, which is the substance of the complaints. Anyone wanting to commemorate somebody can do so more durably by almost any other means.

Greek catalogues reached Europe through Arabic translation, so most bright star names arrive through Arabic and several describe a position within a constellation figure. Greek letters, catalogue numbers and coordinates cover everything fainter. The International Astronomical Union fixed approved spellings from 2016, and commercial star naming services confer nothing any catalogue recognises.