Variable star designation
Variable stars are designated using a variation on the Bayer designation format of an identifying label (as described below) combined with the Latin genitive of the name of the constellation in which the star lies. See List of constellations for a list of constellations and the genitive forms of their names.
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.
- Use AA...AZ, BB...BZ, CC...CZ and so on until reaching QZ, omitting J in both the first and second positions.
- Abandon the Latin script after 334 combinations of letters and start naming stars with V335, V336, and so on.
Note that the second letter is never further up the alphabet than the first, that is to say no star can be BA, CA, CB, DA or so on.
Most newly discovered variable stars will initially be assigned only a catalog designation by their discovers, hence the "names" OT J155631.0-080440 and SDSS J110014.72+131552.1 for two recently discovered objects. These stars will eventually receive names in the format described above.
In the early 19th century few variable stars were known, so it seemed reasonable to use the letters of the Latin script. Because no constellation has a 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. This system of astronomical 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 other categories of astronomical objects the task of assigning names to variable stars is assigned to the International Astronomical Union (IAU). The IAU, in turn, delegates the task to the Sternberg Astronomical Institute in Moscow, Russia. Sternberg publishes the General Catalog of Variable Stars (GCVS), which is periodically (approximately once every two years) amended 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 2161 recently discovered variable stars; these brought the total number of variable stars in the GCVS to 45,678. Among the newly designated objects were V0654 Aurigae, V1367 Centauri, and BU Coronae Borealis.
- "The names and catalogues of variable stars". Les étoiles variables - The variable stars. Retrieved 2005-11-06.