- noun a system of identifying stars
- Numerous overlapping systems are used to identify the stars in the sky. The oldest is simply to give conspicuous stars a name. Most proper names for stars are old, in many cases handed to us via Arab countries in the Middle Ages, and such names are replete with history and meaning. The first systematic approach to the names of stars was pioneered by Bayer in the 17th century. He gave the stars designations consisting of a letter of the Greek alphabet – usually starting with Alpha for the brightest – and the genitive of the name of its constellation. So Alpa Canis Minoris is the brightest star in Canis Minor. (This is why the genitives of constellation names are given in this dictionary under the entry for each constellation.) This system works well for the brightest stars but collapses completely for the large number of stars which became apparent once telescopes entered use. In this century the Henry Draper (HD) catalogue and its extension (HDE) have described by position over 250,000 stars with their spectral type and magnitude. There are also catalogues of variable stars, which begin obscurely at R for each constellation and run to Z, then starting with SS to SZ, TS to ZZ etc, then starting again with AA to AZ, BA to BZ etc. When this runs out – at the 334th variable per constellation – the followers are simply called V335 etc, which might have been a better idea to start with. There are also special catalogues like SS (of strong spectral line stars, called for the authors’ initials), of nebulae (Messier and the New General Catalogue), of radio objects (3C for the third Cambridge catalogue), X-ray sources (numbered by constellation eg Sco X-1 for the first source found in Scorpius), a variety of modern catalogues which list objects simply by position, and a number of catalogues of particular classes of object drawn up by astronomers and often called after their surnames.