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Process by which stars are named
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 (IAU) 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 (usually colloquial) 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.

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.

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 (or less often Latin) 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 (though there are many exceptions). 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 (1879), 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 star catalogues detach the star designation from the star's constellation and aim at enumerating all stars with apparent magnitude greater than a given cut off value. The Histoire céleste française (1801) enumerated 47,390 stars to magnitude 9. The Bonner Durchmusterung (1859) 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 (1892) and the Cape Photographic Durchmusterung (1896). The Henry Draper Catalogue (1924) 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 (2008) contains 945 million stars to magnitude 21.

Variable stars that do not have Bayer designations are assigned designations in a variable star scheme that superficially extends the Bayer scheme with uppercase Latin letters followed by constellation names, starting with single letters R to Z, and proceeding to pairs of letters. Such designations mark them as variable stars. Examples include R Cygni, RR Lyrae, and GN Andromedae. (Many variable stars also have designations in other catalogues.)

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.

Star naming rights are not available for sale via the IAU or any other scientific body. 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 nick names to stars within their own private catalogs. These names are used only by that company and are only available for viewing on their web site or on purchased items. Names by commercial entities are not recognized by the astronomical community, or by competing star naming companies. The New York City Department of Consumer Affairs has issued violation notices against companies which claimed to sell stars or the naming rights to them. A survey conducted by amateur astronomers discovered that just over half 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.