Editing Astronomical naming conventions (section)

== Stars ==
{{main|Stellar designation}}

There are no more than a few thousand stars that appear sufficiently bright in Earth's sky to be visible to the [[naked-eye stars|naked eye]]. This represents the number of stars available to be named by ancient cultures. The upper boundary to what is physiologically possible to be seen with the unaided eye is an apparent [[Magnitude (astronomy)|magnitude]] of 6, or about ten thousand stars. 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. The earliest naming system which is still popular is the [[#Bayer designation|Bayer designation]] using the name of [[#Constellations|constellations]] to identify the stars within them.<ref name="iau-stars">{{cite web |title=Naming Stars IAU|url=https://www.iau.org/public/themes/naming_stars|publisher=International Astronomical Union}}</ref>

The IAU is the only internationally recognized authority for assigning astronomical designations to [[celestial object]]s and surface features on them.<ref name="iau-about">{{cite web |title=About the IAU |url=https://www.iau.org/administration/about|publisher=International Astronomical Union}}</ref> The purpose of this is to ensure that names assigned are unambiguous. There have been many historical [[star catalogue]]s, and new star catalogues are set up on a regular basis as new sky surveys are performed. All designations of objects in recent star catalogues start with an "initialism", which is kept globally unique by the IAU. Different star catalogues then have different naming conventions for what goes after the initialism, but modern catalogs tend to follow a set of generic rules for the data formats used.

The IAU does not recognize the commercial practice of selling fictitious star names by commercial [[International Star Registry|star-naming companies]].<ref name="iau-buying">{{cite web |title=Buying Stars and Star Names |url=https://www.iau.org/public/themes/buying_star_names|publisher=International Astronomical Union}}</ref>

=== Proper names  ===
{{see also|Stellar designation#Proper names|List of proper names of stars}}

There are about 300 to 350 stars with traditional or historical proper names. They tend to be the [[List of brightest stars|brightest stars]] in the sky and are often the most prominent ones of the [[#Constellations|constellation]]. Examples are [[Betelgeuse]], [[Rigel]] and [[Vega]]. Most such names are derived from the [[Arabic language]] ''(see [[List of Arabic star names#History of Arabic star names|List of Arabic star names §&thinsp;History of Arabic star names]])''.

Stars may have multiple proper names, as many different cultures named them independently. [[Polaris]], for example, has also been known by the names ''Alruccabah'', ''Angel Stern, Cynosura'', the ''Lodestar'', ''Mismar'', ''Navigatoria'', ''Phoenice'', the ''Pole Star'', the ''Star of Arcady'', ''Tramontana'' and ''Yilduz'' at various times and places by different cultures in human history.

In 2016, the [[IAU]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web |title=IAU Working Group on Star Names (WGSN) |url=https://www.iau.org/science/scientific_bodies/working_groups/280|publisher=International Astronomical Union}}</ref> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> included a table of the first two batches of names approved by the WGSN (on 30 June and 20 July 2016) together with names of stars adopted by the IAU Executive Committee Working Group on Public Naming of Planets and Planetary Satellites during the 2015 NameExoWorlds campaign<ref>{{cite press release |url=http://www.iau.org/news/pressreleases/detail/iau1514/ |title=Final Results of NameExoWorlds Public Vote Released |publisher=IAU.org |date=15 December 2015 |archive-url=https://web.archive.org/web/20221110180753/https://www.iau.org/news/pressreleases/detail/iau1514/ |archive-date=2022-11-10}}</ref> and recognized by the WGSN. Further batches of names were approved on 21 August 2016, 12 September 2016 and 5 October 2016. These were listed in a table included in the WGSN's second bulletin issued in October 2016.<ref name="WGSN2">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin2.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 2 |access-date=12 October 2016}}</ref> The next additions were done on 1 February, 30 June, 5 September and 19 November 2017, and on 6 June 2018. All are included on the current List of IAU-approved Star Names.<ref name="IAU-LSN">{{cite web |title=Naming Stars |url=https://www.iau.org/public/themes/naming_stars|publisher=International Astronomical Union}}</ref>

The star nearest to Earth 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 usually called by its [[Latin]] name, Sol, in science fiction.

==== Named after people ====
{{Main|Stars named after people#Nomenclature}}

There are about two dozen stars such as [[Barnard's Star]] and [[Kapteyn's Star]] that have historic names and which were named in honor after [[astronomer]]s. As a result of the NameExoWorlds campaign in December 2015 the IAU approved the names Cervantes (honoring the writer [[Miguel de Cervantes]]) and Copernicus (honoring the astronomer [[Nicolaus Copernicus]]) for the stars [[Mu Arae]] and [[55 Cancri|55 Cancri A]], respectively.<ref name="IAUnames">{{Cite web |url=http://nameexoworlds.iau.org/names |title=NameExoWorlds The Approved Names |access-date=2016-07-28 |archive-date=2018-02-01 |archive-url=https://web.archive.org/web/20180201043609/http://nameexoworlds.iau.org/names |url-status=dead }}</ref> In July 2016, the IAU WGSN approved the name ''Cor Caroli'' ([[Latin (language)|Latin]] for 'heart of Charles') for the star [[Cor Caroli|Alpha Canum Venaticorum]], so named in honour of [[King Charles I of England]] by Sir [[Charles Scarborough]], his physician.<ref>Richard Hinckley Allen, ''[[Star Names|Star-Names and Their Meanings]]'', G.E. Stechert, New York, 1899</ref><ref>Robert Burnham, Jr. ''Burnham's Celestial Handbook'', Volume 1, p. 359.</ref><ref>[http://www.ianridpath.com/startales/canesvenatici.html#corcaroli Ian Ridpath: "Star Tales", Canes Venatici]. See also Deborah J. Warner, ''The Sky Explored: Celestial Cartography 1500-1800''.</ref> In 2019, IAU held the [[NameExoWorlds]] campaign.<ref>{{Cite web|url=https://www.nameexoworlds.iau.org/final-results|title=Approved names|website=NameExoworlds|language=en|access-date=2020-01-02}}</ref>

=== Catalogues ===
{{main|Star catalogue}}

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 [[Stellar designation|designations]] assigned to them by a variety of different [[star catalogue]]s. Older catalogues either assigned an arbitrary number to each object, or used a simple systematic naming scheme based on the constellation the star lies in, like the older [[Ptolemy]]'s Almagest in Greek from [[AD 150|150]] and [[Abd al-Rahman al-Sufi|Al-Sufi]]'s [[Book of Fixed Stars]] in Arabic from 964. The variety of sky catalogues in use means that most bright stars have multiple designations.

In 1540, the Italian astronomer [[Alessandro Piccolomini|Piccolomini]] released the book ''De le Stelle Fisse'' (On the Fixed Stars) which include star maps of 47 constellations where he numbered the stars in magnitude order using latin letters.<ref name="ridpath">{{cite web |last=Ridpath |first=Ian |title=Alessandro Piccolomini's star atlas |url=http://www.ianridpath.com/startales/piccolomini.html}}</ref> 

==== Bayer designation ====
{{main|Bayer designation|Table of stars with Bayer designations}}

The [[Bayer designation]]s of about 1,500 brightest stars were first published in 1603. In this list, a star is identified by a lower-case [[Greek alphabet#Letters|letter of the Greek alphabet]], followed by the Latin name of its parent constellation. The Bayer designation uses the possessive form of a constellation's name, which in almost every case ends in ''is'', ''i'' or ''ae''; ''um'' if the constellation's name is plural ''(see [[88 modern constellations#Modern constellations|genitive case for constellations]])''. In addition, a three-letter abbreviation is often used . Examples include [[Alpha&nbsp;Andromedae]] (''α And'') in the constellation of Andromeda, [[Alpha&nbsp;Centauri]] (''α Cen''), in the constellation Centaurus, [[Alpha&nbsp;Crucis]] (''α Cru'') and [[Beta&nbsp;Crucis]] (''β Cru''), the two brightest stars in the constellation Crux, the Southern Cross, [[Epsilon&nbsp;Carinae]] (''ε Car'') in Carina, [[Lambda&nbsp;Scorpii]] (''λ Sco'') in Scorpius  and [[Sigma&nbsp;Sagittarii]] (''σ Sgr'') in Sagittarius. After all twenty-four Greek letters have been assigned, upper and lower case Latin letters are used, such as for [[A&nbsp;Centauri]] (''A Cen''), [[D&nbsp;Centauri]] (''D Cen''), [[G&nbsp;Scorpii]] (''G Sco''), [[P Cygni]] (''P Cyg''), [[b&nbsp;Sagittarii]] (''b Sgr''), [[HD 117440|d&nbsp;Centauri]] (''d Cen'') and [[HD 90853|s&nbsp;Carinae]] (''s Car'').

As the resolving power of telescopes increased, numerous objects that were thought to be a single object were found to be optical [[star system]]s that were too closely spaced in the sky to be discriminated by the human eye. This led to a third iteration, where numeric superscripts were added to distinguish those previously unresolved stars. Examples include [[Theta Sagittarii]] (''θ Sgr'') later distinguished as Theta¹ Sagittarii (''θ¹ Sgr'') and Theta² Sagittarii (''θ² Sgr''), each being their own (physical) star system with two and three stars, respectively.

==== Flamsteed designation ====
{{Further|List of constellations using Flamsteed star designations}}

[[Flamsteed designation]]s consist of a number and the Latin genitive of the constellation the star lies in. Examples include [[51 Pegasi]] and [[61 Cygni]]. About 2,500 stars are catalogued. They are commonly used when no Bayer designation exists, or when the Bayer designation uses numeric superscripts such as in [[Rho1 Cancri|Rho¹&nbsp;Cancri]]. In this case, the simpler Flamsteed designation, [[55 Cancri]], is often preferred.

==== Modern catalogues ====
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&nbsp;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&minus;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]] ([[astronomical epoch|epoch]] 'J', [[right ascension]] 15{{sup|h}}32{{sup|m}}59.96{{sup|s}}, [[declination]] &minus;00°39′44.1″).

=== Variable stars ===
{{main article|Variable star designation}}
Variable stars are assigned designations in a variable star scheme that is based on a variation of the [[Bayer designation]] format, with an identifying label preceding the [[Latin language|Latin]] genitive of the name of the [[constellation]] in which the star lies. Such designations mark them as variable stars. Examples include [[R Cygni]], [[RR Lyrae]], and [[V1331 Cygni]]. The [[International Astronomical Union]] delegates the task to the [[Sternberg Astronomical Institute]] in Moscow, Russia.

=== Compact stars ===

==== Pulsars ====
{{main|Pulsar#Nomenclature}}

[[Pulsar]]s such as [[PSR J0737-3039]], are designated with a "PSR" prefix, that stands for ''Pulsating Source of Radio''. The prefix is followed by the pulsar's [[right ascension]] and degrees of [[declination]]. The right ascension is also prefixed with a "J" ([[Julian epoch]]) or a "B" ([[Epoch (astronomy)#Besselian epoch|Besselian Epochs]]) used prior to 1993, as in [[PSR B1257+12]].

==== Black holes ====
{{see also|List of black holes}}

Black holes have no consistent naming conventions. [[Supermassive black hole]]s receive the designation of the galaxy whose core they reside in. Examples are [[NGC 4261]], [[NGC 4151]] and [[Andromeda Galaxy#Nucleus|M31]], which derive their designation from the ''[[New General Catalogue]]'' and the list of ''[[Messier objects]]''.

Other black holes, such as [[Cygnus X-1]] – a highly likely [[stellar black hole]], are cataloged by their constellation and the order in which they were discovered. A large number of black holes are designated by their position in the sky and prefixed with the instrument or survey that discovered them.<ref>{{cite web |title=Black Hole Encyclopedia – FAQ |url=http://blackholes.stardate.org/resources/faqs/faq.php?p=black-hole-names |archive-url=https://web.archive.org/web/20210806072246/http://blackholes.stardate.org/resources/faqs/faq.php?p=black-hole-names |archive-date=2021-08-06 |access-date=4 September 2015 |website=StarDate.org}}</ref> Examples are {{nowrap|[[SDSS J0100+2802]]}} (where SDSS stands for [[Sloan Digital Sky Survey]]), and [[RX J1131-1231|RX&nbsp;J1131&minus;1231]], observed by the [[Chandra X-ray Observatory]].<ref>{{cite web |date=10 August 2015 |title=Chandra images by category: Black holes |url=http://chandra.harvard.edu/photo/category/blackholes.html |archive-url=https://web.archive.org/web/20221205090958/https://chandra.harvard.edu/photo/category/blackholes.html |archive-date=2022-12-05 |publisher=Harvard-Smithsonian Center for Astrophysics}}</ref>

=== Supernovae ===
{{see also|Supernova#Naming convention|l1=Naming and classification of supernovae}}

[[Supernova]] discoveries are reported to the IAU's ''[[Central Bureau for Astronomical Telegrams]]'' and are automatically given a provisional designation based on the co-ordinates of the discovery. Historically, when supernovae are identified as belonging to a "type", CBAT has also published circulars with assigned year–letter designations, and discovery details. A supernova's permanent designation is formed by the standard prefix "SN", the year of discovery, and a suffix composed of one to three letters of the Latin alphabet. The first 26 supernovae of the year receive a capital letter from ''A'' to ''Z''. Subsequent supernovae of that year are designated with pairs of lower-case letters from "aa" to "az", and then continuing with "ba" until "zz". Then come "aaa", "aab", and so on (this first occurred in 2015-2016)<!-- Asiago Supernova Catalogue for 2015 (http://graspa.oapd.inaf.it/cgi-bin/sncat_new.cgi?yr=2015) runs up to 2015dd and then jumps to 2016aai, 2016dpd, and 2016fq -->. For example, the prominent [[SN&nbsp;1987A]], was the first one to be observed in 1987, while [[SN 2023ixf]] was one of the brightest ever observed in recent times. Several thousand supernovae have been reported since 1885.<ref name="cbat-SN-list" /> In recent years, several supernova discovery projects have retained their more distant supernova discoveries for in-house follow-up, and not reported them to CBAT. Starting in 2015, CBAT has scaled back its efforts to publish assigned designations of typed supernovae: By September 2014, CBAT had published names and details of 100 supernovae discovered in that year. By September 2015, CBAT had only published names of 20 supernovae discovered in that year. The [[Astronomer's Telegram]] provides some surrogate services independent from CBAT.

Four historical supernovae are known simply by the year they occurred: [[SN&nbsp;1006]] (the brightest stellar event ever recorded), [[SN&nbsp;1054]] (of which the remnant is the [[Crab Nebula]] and the [[Crab Pulsar]]), [[SN&nbsp;1572]] (''Tycho's Nova''), and [[SN&nbsp;1604]] (''Kepler's Star'').

Since 1885, the letter-suffixes are explicitly assigned, regardless whether only one supernova is detected during the entire year (although this has not occurred since 1947). Driven by advances in technology and increases in observation time in the early 21st century, hundreds of supernovae were reported every year to the IAU, with more than 500 catalogued in 2007.<ref name="cbat-SN-list">{{cite web|url=http://cbat.eps.harvard.edu/lists/Supernovae.html |title=List of Supernovae |publisher=Cbat.eps.harvard.edu |access-date=4 September 2015}}</ref> Since then, the number of newly discovered supernovae has increased to thousands per year, for example almost 16,000 supernovae observations were reported in 2019, more than 2,000 of which were named by CBAT.<ref>{{cite web |last=Bishop |first=David |title=Supernova discovery statistics for 2019 |url=http://www.rochesterastronomy.org/sn2019/snstats.html |archive-url=https://web.archive.org/web/20201120085934/http://www.rochesterastronomy.org/sn2019/snstats.html |archive-date=2020-11-20 |access-date=14 March 2021 |publisher=Rochester Academy of Science, Astronomy Section}}</ref>

=== Novae ===
{{main|List of novae in the Milky Way galaxy#Nomenclature}}