Stellar designations and names
In astronomy, stars have a variety of different stellar designations and names, including catalogue designations, current and historical proper names, and foreign language names.
Only a tiny minority of known stars have proper names; all others have only designations from various catalogues or lists, or no identifier at all. Hipparchus in the 2nd century BC enumerated about 850 naked-eye stars. Johann Bayer in 1603 listed about twice this number. Only in the 19th century did star catalogues list the naked-eye stars exhaustively. The Bright Star Catalogue, which is a star catalogue listing all stars of apparent magnitude 6.5 or brighter, or roughly every star visible to the naked eye from Earth, contains 9,096 stars. The most voluminous modern catalogues list on the order of a billion stars, out of an estimated total of 200 to 400 billion in the Milky Way.
Proper names may be historical, often transliterated from Arabic or Chinese names. Such transliterations can vary so there may be multiple spellings. A smaller number of names have been introduced since the Middle Ages, and a few in modern times as nicknames have come into popular use, for example Sualocin for α Delphini and Navi for γ Cassiopeiae.
The International Astronomical Union has begun a process to select and formalise unique proper names for the brighter naked-eye stars and for other stars of popular interest. To the IAU, name refers to the term used for a star in everyday speech, while "designation is solely alphanumerical" and used almost exclusively in official catalogues and for professional astronomy. Many of the names and some of the designations in use today were inherited from the time before the IAU existed. Other designations are being added all the time. As of the start of 2019, the IAU had decided on a little over 300 proper names, mostly for the brighter naked-eye stars.
Proper names
Several hundred of the brightest stars had traditional names, most of which derived from Arabic, but a few from Latin. There were a number of problems with these names, however:- Spellings were often not standardized
- Many stars had more than one name of roughly equal popularity
- Because of imprecision in old star catalogs, it was not always clear exactly which star within a constellation a particular name corresponded to.
- Some stars in entirely different constellations had the same name: Algenib in Perseus and Algenib in Pegasus; Gienah in Cygnus and Gienah in Corvus, Alnair in Grus and Alnair in Centaurus.
In practice, names are only universally used for the very brightest stars and for a small number of slightly less bright but "interesting" stars. For other naked eye stars, the Bayer or Flamsteed designation is often preferred.
In addition to the traditional names, a small number of stars that are "interesting" can have modern English names. For instance, two second-magnitude stars, Alpha Pavonis and Epsilon Carinae, were assigned the proper names Peacock and Avior respectively in 1937 by Her Majesty's Nautical Almanac Office during the creation of The Air Almanac, a navigational almanac for the Royal Air Force. Of the fifty-seven stars included in the new almanac, these two had no traditional names. The RAF insisted that all of the stars must have names, so new names were invented for them. These names have been approved by the IAU WGSN.
The book by R. H. Allen has had effects on star names:
- It lists many Assyrian/Babylonian and Sumerian star names recovered by archaeology, and some of these have since been approved by the IAU WGSN.
- It lists many Chinese star names, though these have not come into general usage.
- Allen represented the "kh" sound by 'h' with a dot above and at least one astronomy book, using Allen as a source, has misread this unfamiliar letter as 'li'.
Stars named for individuals
In July 2014 the IAU launched a process for giving proper names to exoplanets and their host stars. As a result, the IAU approved the names Cervantes for Mu Arae and Copernicus for 55 Cancri A.
Catalogue designations
In the absence of any better means of designating a star, catalogue designations are generally used. Many star catalogues are used for this purpose; see star catalogues.By constellation
The first modern schemes for designating stars systematically labelled them within their constellation.- The Bayer designation is such a system, published by Johann Bayer in 1603. It introduced a system of designating the brightest stars in each constellation by means of Greek letters, and is still widely used. Bayer generally assigned letters by magnitude class: 1st magnitude stars received the earliest letters in the alphabet, followed by 2nd magnitude stars, and so forth. The original list of Bayer designations contained 1,564 naked-eye stars, and several stars not catalogued by Bayer have been added by subsequent astronomers.
- The Flamsteed designation also lists stars by constellation, but by number rather than letter, ordering them by increasing right ascension rather than by decreasing brightness. These numbers were assigned not by Flamsteed himself but by the French astronomer J. J. Lalande in a French edition of Flamsteed's catalogue published in 1783.
- The Gould designation for stars visible from the southern hemisphere, introduced by Benjamin Gould, also lists stars by constellation, numbered by increasing right ascension.
- Hevelius and Bode both numbered stars within constellations similarly. Their number systems have fallen out of use, but their designations even now are occasionally mistakenly treated as Flamsteed designations. 47 Tucanae, a number assigned by Bode, is a famous example.
Full-sky catalogues
- The Histoire Céleste Française enumerated 47,390 stars to magnitude 9.
- The Bonner Durchmusterung was the most complete star catalogue compiled without the aid of photography. It listed a total of 320,000 northern stars, expanded by the Cordoba Durchmusterung and the Cape Photographic Durchmusterung.
- The Henry Draper Catalogue listed 225,300 stars to magnitude 10, extended to a total of 359,083 in 1949. The HD numbers remain in widespread use for stars that do not have a Flamsteed or Bayer designation.
- The Bright Star Catalogue of 1930 listed all stars brighter than magnitude 6. It was supplemented to include stars down to magnitude 7.1 in 1983.
- The Catalogue astrographique was compiled between 1891 and 1950 with the aim of listing all stars to magnitude 11, resulting in a list of 4.6 million stars. It is under continued development, now under custody of the U.S. Naval Observatory.
- The USNO-B1.0 catalogue contains over a billion objects, and is also under continued development at the U.S. Naval Observatory.
- The online Guide Star Catalog II contains 945 million stars to magnitude 21.
Variable designations
Exoplanet searches
When a planet is detected around a star, the star is often given a name and number based on the name of the telescope or survey mission that discovered it and based on how many planets have already been discovered by that mission e.g. HAT-P-9, WASP-1, COROT-1, Kepler-4, TRAPPIST-1.Sale of star names by non-scientific entities
Star naming rights are not available for sale via the IAU. Rather, star names are selected on a non-commercial basis by a small number of international organizations of astronomers, scientists, and registration bodies, who assign names consisting usually of a Greek letter followed by the star's constellation name, or less frequently based on their ancient traditional name.However, there are a number of non-scientific "star-naming" companies that offer to assign personalized names to stars within their own private catalogs. These names are used only within that company, and are not recognized by the astronomical community, or by competing star-naming companies. A survey conducted by amateur astronomers discovered that 54% of consumers would still want to "name a star" with a non-scientific star-naming company even though they have been warned or informed such naming is not recognized by the astronomical community.