Astronomical Naming Conventions - Names of Stars

Names of Stars

According to the IAU, apart from a limited number of bright stars with historic names, stars do not have proper names. Where historic names exist, these names are, with a few exceptions, taken from the Arabic language due to their lead in the beginning of modern astronomy. See List of traditional star names for examples.

There are no more than a few thousand stars that appear sufficiently bright in the Earth's sky to be visible to the naked eye, so this represents the limit of the possible number of stars available to be named by ancient cultures. This limit is approximate, as it varies by the acuity of any given observer's eyes, but ten thousand stars (the naked-eye stars to visual magnitude six) seems to be an upper bound to what is physiologically possible.

Estimates of the number of stars with recognised proper names range from 300 to 350 different stars. These tend to be the brightest stars, or stars that form part of constellation patterns with the brightest stars. The number of proper names for stars is greater than the number of stars with proper names, as many different cultures named stars independently. For example, the star known as Polaris has also at various times and places been known by the names Alruccabah, Angel Stern, Cynosura, the Lodestar, Mismar, Navigatoria, Phoenice, the Pole Star, the Star of Arcady, Tramontana and Yilduz.

With the advent of the increased light-gathering abilities of the telescope, many more stars became visible, far too many to all be given names. Instead, they have designations assigned to them by a variety of different star catalogues. Older catalogues either assigned an arbitrary number to each object, or used a simple systematic naming scheme such as combining constellation names with Greek letters. Multiple sky catalogues meant that some stars had more than one designation. For example, the star with the Arabic name of Rigil Kentaurus also has the Bayer designation of Alpha Centauri.

As the resolving power of telescopes increased, numerous objects that were thought to be a single object were found to be multiple star systems that were too closely spaced in the sky to be discriminated by the human eye. These and other confusions make it essential that great care is taken in using designations. For example, Rigil Kentaurus contains three stars in a triple star system, labelled Rigil Kentaurus A, B and C respectively.

Most modern catalogues are generated by computers, using high-resolution, high-sensitivity telescopes, and as a result describe very large numbers of objects. For example, the Guide Star Catalog II has entries on over 998 million distinct astronomical objects. Objects in these catalogs are typically located with very high resolution, and assign designations to these objects based on their position in the sky. An example of such a designation is SDSSp J153259.96-003944.1, where the initialism SDSSp indicates that the designation is from the "Sloan Digital Sky Survey preliminary objects", and the other characters indicate celestial coordinates.

The star nearest to Earth, our Sun, is typically referred to simply as "the Sun" or its equivalent in the language being used (for instance, if two astronomers were speaking French, they would call it le Soleil). However, it is sometimes called by its Latin name, Sol.

Finally, there are a few stars named after people.