The Naming of Stars

Astronomers use a number of conventions to name stars. Most conventions have their origins hundreds of years ago. All star names and designations must be approved by the International Astronomical Union. The Centre de Données astronomiques de Strasbourg (CDS) provides a Dictionary of Nomenclature of Celestial Objects.

The following are some standard nomenclatures for stars.

The arabic, Bayer, and Flamsteed designations exist only for the very brightest, visible. stars in the sky. Most stars are known by catalog names. Common star catalogs include:

Most bright stars have many names. Betelgeuse is also known as <em>alpha</em> Ori, 58 Ori, BD+7 1055, HR2061, HD39801, and SAO113271. There are other names too, including entries in double star and variable star catalogs.

Variable Stars

Variable stars are named by constellation, and in the order that they are identified. The first variable star in a constellation is called R (e.g., R Mon), the second S, and so on through Z. That works for 9 stars. The next set uses two letter designations, beginning with RR, followed by RS through RZ, then SS through SZ and so on to ZZ. Then one goes to AA ... AZ, BB ... BZ ... QZ. This can account for 334 variable stars in a constellation. Since there are often many more than this, variable stars after QZ are designated as V followed by the number of variables. The variable star after QZ Tau is V335 Tau. There are over 2000 variable stars catalogued in Sagittarius alone!

Bright stars, even if variable, do not get variable star names. The eclipsing variable Algol goes by its Bayer designation, <em>beta</em> Per, in the Catalog of Variable Stars.