astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

, a variable-star designation is a unique identifier given to

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

s. It extends the

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

format, with an identifying label (as described below) preceding the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

genitive In grammar, the genitive case ( abbreviated ) is the grammatical case that marks a word, usually a noun, as modifying another word, also usually a noun—thus indicating an attributive relationship of one noun to the other noun. A genitive can ...

of the name of the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

in which the star lies. The identifying label can be one or two

letters or a ''V'' plus a number (e.g. V399). Examples are R Coronae Borealis, YZ Ceti, V603 Aquilae. (''See'' List of constellations ''for a list of constellations and the genitive forms of their names''.)

Naming

The current naming system is: * Stars with existing Greek letter Bayer designations are not given new designations. * Otherwise, start with the letter R and go through Z. * Continue with RR–RZ, then use SS–SZ, TT–TZ and so on until ZZ. * After ZZ return to the beginning of the Latin alphabet and use AA–AZ, BB–BZ, CC–CZ, and so on, until reaching QZ, but omitting the letter J in either first or second position. * Abandon the Latin letters after all 334 combinations of letters and start naming stars with V335, V336, and so on. The second letter is never nearer the beginning of the

alphabet An alphabet is a standard set of letter (alphabet), letters written to represent particular sounds in a spoken language. Specifically, letters largely correspond to phonemes as the smallest sound segments that can distinguish one word from a ...

than the first, e.g., no star can be BA, CA, CB, DA and so on.

History

In the early 19th century few variable stars were known, so it seemed reasonable to use the letters of the

Latin script The Latin script, also known as the Roman script, is a writing system based on the letters of the classical Latin alphabet, derived from a form of the Greek alphabet which was in use in the ancient Greek city of Cumae in Magna Graecia. The Gree ...

. Because very few constellations contained stars with uppercase Latin-letter Bayer designation greater than Q, the letter R was chosen as a starting point so as to avoid confusion with letter spectral types or the (now rarely used) Latin-letter Bayer designations. Although Lacaille had used uppercase R–Z letters in a few cases, for example X Puppis (HR 2548), these designations were either dropped or accepted as variable star designations. The star T Puppis was accepted by Argelander as a variable star and is included in the General Catalogue of Variable Stars with that designation but is now classed as non-variable. This variable star naming convention was developed by Friedrich W. Argelander. There is a widespread belief according to which Argelander chose the letter R for German ''rot'' or French ''rouge'', both meaning "red", because many variable stars known at that time appear red. However, Argelander's own statement disproves this. By 1836, even the letter S had only been used in one constellation, Serpens. With the advent of photography the number of variables piled up quickly, and variable star names soon fell into the Bayer-trap of reaching the end of the alphabet while still having stars to name. After two subsequent supplementary double-lettering systems hit similar limits, numbers were finally introduced. As with all categories of astronomical objects, names are assigned by the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

(IAU). The IAU delegates the task to the Sternberg Astronomical Institute and the Institute of Astronomy of the Russian Academy of Sciences in Moscow, Russia. Sternberg publishes the ''General Catalog of Variable Stars'' (), which is amended approximately once every two years by the publication of a new ''Name-List of Variable Stars''. For example, in December 2011, the 80th ''Name-List of Variable Stars'', Part II, was released, containing designations for 2,161 recently discovered variable stars, which brought the total number in the to 45,678 variable stars. Among the newly designated objects were V0654 Aurigae, V1367 Centauri, and BU Coronae Borealis.

Naming

History

Footnotes

See also

References

Further reading