# Variable-star designation

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{{Short description|Unique identifier given to variable stars}}
In [astronomy](/source/astronomy), a '''variable-star designation''' is a unique identifier given to [variable star](/source/variable_star)s.  It extends the [Bayer designation](/source/Bayer_designation) format, with an identifying label (as described below) preceding the [Latin](/source/Latin_language) [genitive](/source/genitive_case) of the name of the [constellation](/source/constellation) in which the star lies. The identifying label can be one or two [Latin](/source/Latin_script) letters or a ''V'' plus a number (e.g. V399). Examples are [R Coronae Borealis](/source/R_Coronae_Borealis), [YZ Ceti](/source/YZ_Ceti), [V603 Aquilae](/source/V603_Aquilae). (''See'' [List of constellations](/source/List_of_constellations) ''for a list of constellations and the genitive forms of their names''.)

==Naming==
The current naming system is:<ref name=levy/>
* Stars with existing Greek letter Bayer designations are not given new designations.
* Otherwise, start with the letter R and go through Z.
* Continue with RR–RZ, then use SS–SZ, TT–TZ and so on until ZZ.
* After ZZ return to the beginning of the Latin alphabet and use AA–AZ, BB–BZ, CC–CZ, and so on, until reaching QZ, but omitting the letter&nbsp;J in either first or second position.{{efn|
Most of this system was invented in [Germany](/source/Germany), which was still on [Fraktur](/source/Fraktur_(typeface_sub-classification)) at the time, in which the [majuscule](/source/majuscule)s "I" and "J" can be difficult to distinguish.
}} The second letter is never nearer the beginning of the [alphabet](/source/alphabet) than the first, e.g., no star can be BA, CA, CB, DA and so on.
* Abandon the Latin letters after all 334&nbsp;combinations of letters and start naming stars with V335, V336, and so on.
* After the combination/number, put the genitive of the constellation name (e.g. [Centaurus](/source/Centaurus) becomes Centauri, [Orion](/source/Orion_(constellation)) becomes Orionis) to get the star name.
{| class="wikitable mw-collapsible mw-collapsed"
|+List of variable star designations
!Variable Number
!Designation
|-
|1
|R
|-
|2
|S
|-
|3
|T
|-
|4
|U
|-
|5
|V
|-
|6
|W
|-
|7
|X
|-
|8
|Y
|-
|9
|Z
|-
|10
|RR
|-
|11
|RS
|-
|12
|RT
|-
|13
|RU
|-
|14
|RV
|-
|15
|RW
|-
|16
|RX
|-
|17
|RY
|-
|18
|RZ
|-
|19
|SS
|-
|20
|ST
|-
|21
|SU
|-
|22
|SV
|-
|23
|SW
|-
|24
|SX
|-
|25
|SY
|-
|26
|SZ
|-
|27
|TT
|-
|28
|TU
|-
|29
|TV
|-
|30
|TW
|-
|31
|TX
|-
|32
|TY
|-
|33
|TZ
|-
|34
|UU
|-
|35
|UV
|-
|36
|UW
|-
|37
|UX
|-
|38
|UY
|-
|39
|UZ
|-
|40
|VV
|-
|41
|VW
|-
|42
|VX
|-
|43
|VY
|-
|44
|VZ
|-
|45
|WW
|-
|46
|WX
|-
|47
|WY
|-
|48
|WZ
|-
|49
|XX
|-
|50
|XY
|-
|51
|XZ
|-
|52
|YY
|-
|53
|YZ
|-
|54
|ZZ
|-
|55
|AA
|-
|56
|AB
|-
|57
|AC
|-
|58
|AD
|-
|59
|AE
|-
|60
|AF
|-
|61
|AG
|-
|62
|AH
|-
|63
|AI
|-
|64
|AK
|-
|65
|AL
|-
|66
|AM
|-
|67
|AN
|-
|68
|AO
|-
|69
|AP
|-
|70
|AQ
|-
|71
|AR
|-
|72
|AS
|-
|73
|AT
|-
|74
|AU
|-
|75
|AV
|-
|76
|AW
|-
|77
|AX
|-
|78
|AY
|-
|79
|AZ
|-
|80
|BB
|-
|81
|BC
|-
|82
|BD
|-
|83
|BE
|-
|84
|BF
|-
|85
|BG
|-
|86
|BH
|-
|87
|BI
|-
|88
|BK
|-
|89
|BL
|-
|90
|BM
|-
|91
|BN
|-
|92
|BO
|-
|93
|BP
|-
|94
|BQ
|-
|95
|BR
|-
|96
|BS
|-
|97
|BT
|-
|98
|BU
|-
|99
|BV
|-
|100
|BW
|-
|101
|BX
|-
|102
|BY
|-
|103
|BZ
|-
|104
|CC
|-
|105
|CD
|-
|106
|CE
|-
|107
|CF
|-
|108
|CG
|-
|109
|CH
|-
|110
|CI
|-
|111
|CK
|-
|112
|CL
|-
|113
|CM
|-
|114
|CN
|-
|115
|CO
|-
|116
|CP
|-
|117
|CQ
|-
|118
|CR
|-
|119
|CS
|-
|120
|CT
|-
|121
|CU
|-
|122
|CV
|-
|123
|CW
|-
|124
|CX
|-
|125
|CY
|-
|126
|CZ
|-
|127
|DD
|-
|128
|DE
|-
|129
|DF
|-
|130
|DG
|-
|131
|DH
|-
|132
|DI
|-
|133
|DK
|-
|134
|DL
|-
|135
|DM
|-
|136
|DN
|-
|137
|DO
|-
|138
|DP
|-
|139
|DQ
|-
|140
|DR
|-
|141
|DS
|-
|142
|DT
|-
|143
|DU
|-
|144
|DV
|-
|145
|DW
|-
|146
|DX
|-
|147
|DY
|-
|148
|DZ
|-
|149
|EE
|-
|150
|EF
|-
|151
|EG
|-
|152
|EH
|-
|153
|EI
|-
|154
|EK
|-
|155
|EL
|-
|156
|EM
|-
|157
|EN
|-
|158
|EO
|-
|159
|EP
|-
|160
|EQ
|-
|161
|ER
|-
|162
|ES
|-
|163
|ET
|-
|164
|EU
|-
|165
|EV
|-
|166
|EW
|-
|167
|EX
|-
|168
|EY
|-
|169
|EZ
|-
|170
|FF
|-
|171
|FG
|-
|172
|FH
|-
|173
|FI
|-
|174
|FK
|-
|175
|FL
|-
|176
|FM
|-
|177
|FN
|-
|178
|FO
|-
|179
|FP
|-
|180
|FQ
|-
|181
|FR
|-
|182
|FS
|-
|183
|FT
|-
|184
|FU
|-
|185
|FV
|-
|186
|FW
|-
|187
|FX
|-
|188
|FY
|-
|189
|FZ
|-
|190
|GG
|-
|191
|GH
|-
|192
|GI
|-
|193
|GK
|-
|194
|GL
|-
|195
|GM
|-
|196
|GN
|-
|197
|GO
|-
|198
|GP
|-
|199
|GQ
|-
|200
|GR
|-
|201
|GS
|-
|202
|GT
|-
|203
|GU
|-
|204
|GV
|-
|205
|GW
|-
|206
|GX
|-
|207
|GY
|-
|208
|GZ
|-
|209
|HH
|-
|210
|HI
|-
|211
|HK
|-
|212
|HL
|-
|213
|HM
|-
|214
|HN
|-
|215
|HO
|-
|216
|HP
|-
|217
|HQ
|-
|218
|HR
|-
|219
|HS
|-
|220
|HT
|-
|221
|HU
|-
|222
|HV
|-
|223
|HW
|-
|224
|HX
|-
|225
|HY
|-
|226
|HZ
|-
|227
|II
|-
|228
|IK
|-
|229
|IL
|-
|230
|IM
|-
|231
|IN
|-
|232
|IO
|-
|233
|IP
|-
|234
|IQ
|-
|235
|IR
|-
|236
|IS
|-
|237
|IT
|-
|238
|IU
|-
|239
|IV
|-
|240
|IW
|-
|241
|IX
|-
|242
|IY
|-
|243
|IZ
|-
|244
|KK
|-
|245
|KL
|-
|246
|KM
|-
|247
|KN
|-
|248
|KO
|-
|249
|KP
|-
|250
|KQ
|-
|251
|KR
|-
|252
|KS
|-
|253
|KT
|-
|254
|KU
|-
|255
|KV
|-
|256
|KW
|-
|257
|KX
|-
|258
|KY
|-
|259
|KZ
|-
|260
|LL
|-
|261
|LM
|-
|262
|LN
|-
|263
|LO
|-
|264
|LP
|-
|265
|LQ
|-
|266
|LR
|-
|267
|LS
|-
|268
|LT
|-
|269
|LU
|-
|270
|LV
|-
|271
|LW
|-
|272
|LX
|-
|273
|LY
|-
|274
|LZ
|-
|275
|MM
|-
|276
|MN
|-
|277
|MO
|-
|278
|MP
|-
|279
|MQ
|-
|280
|MR
|-
|281
|MS
|-
|282
|MT
|-
|283
|MU
|-
|284
|MV
|-
|285
|MW
|-
|286
|MX
|-
|287
|MY
|-
|288
|MZ
|-
|289
|NN
|-
|290
|NO
|-
|291
|NP
|-
|292
|NQ
|-
|293
|NR
|-
|294
|NS
|-
|295
|NT
|-
|296
|NU
|-
|297
|NV
|-
|298
|NW
|-
|299
|NX
|-
|300
|NY
|-
|301
|NZ
|-
|302
|OO
|-
|303
|OP
|-
|304
|OQ
|-
|305
|OR
|-
|306
|OS
|-
|307
|OT
|-
|308
|OU
|-
|309
|OV
|-
|310
|OW
|-
|311
|OX
|-
|312
|OY
|-
|313
|OZ
|-
|314
|PP
|-
|315
|PQ
|-
|316
|PR
|-
|317
|PS
|-
|318
|PT
|-
|319
|PU
|-
|320
|PV
|-
|321
|PW
|-
|322
|PX
|-
|323
|PY
|-
|324
|PZ
|-
|325
|QQ
|-
|326
|QR
|-
|327
|QS
|-
|328
|QT
|-
|329
|QU
|-
|330
|QV
|-
|331
|QW
|-
|332
|QX
|-
|333
|QY
|-
|334
|QZ
|-
|335
|V335
|-
|336
|V336
|-
|337
|V337
|-
|338
|V338
|-
| -
|V339, V340, etc.
|}

==History==

In the early 19th&nbsp;century few variable stars were known, so it seemed reasonable to use the letters of the [Latin script](/source/Latin_script). Because very few constellations contained stars with uppercase Latin-letter Bayer designation greater than [Q](/source/Q_Carinae), the letter R was chosen as a starting point so as to avoid confusion with letter spectral types or the (now rarely used) Latin-letter Bayer designations. Although [Lacaille](/source/Nicolas_Louis_de_Lacaille) had used uppercase R–Z&nbsp;letters in a few cases, for example X&nbsp;Puppis (HR&nbsp;2548), these designations were either dropped or accepted as variable star designations.<ref name=wagman/> The star T&nbsp;Puppis was accepted by Argelander as a variable star and is included in the [General Catalogue of Variable Stars](/source/General_Catalogue_of_Variable_Stars) with that designation but is now classed as non-variable.<ref name=coelum/>

This variable star [naming convention](/source/Astronomical_naming_conventions) was developed by [Friedrich W. Argelander](/source/Friedrich_Wilhelm_Argelander). There is a widespread belief according to which Argelander chose the letter&nbsp;R for [German](/source/German_language) ''rot'' or [French](/source/French_language) ''rouge'', both meaning "red", because many variable stars known at that time appear red.<ref name=chapman/> However, Argelander's own statement disproves this.<ref name=cds/>

By 1836, even the letter&nbsp;S had only been used in one constellation, [Serpens](/source/Serpens). With the advent of photography the number of variables piled up quickly, and variable star names soon fell into the Bayer-trap of reaching the end of the alphabet while still having stars to name.{{citation needed|date=April 2020}} After two subsequent supplementary double-lettering systems hit similar limits, numbers were finally introduced.<ref name=cds/>

In 1865, [G. F. Chambers](/source/George_Frederick_Chambers) published a catalogue of 123 variables, all but one of which had a variable star designation in the Argelander scheme.<ref name=Chambers_1865/> The following year, [E. Schönfeld](/source/Eduard_Sch%C3%B6nfeld) published a variable star catalogue with 112 entries; most used the same scheme. This catalogue would not be updated until 1888, when [S. C. Chandler](/source/Seth_Carlo_Chandler) published an update. He released two more updates to this catalogue in 1893 and 1896. The [German Astronomical Society](/source/German_Astronomical_Society) then took over the task of maintaining variable star identifiers by publishing annual updates in the ''[Astronomische Nachrichten](/source/Astronomische_Nachrichten)'' journal.<ref name=Griffin_2015/>

As with all categories of astronomical objects, names are now assigned by the [International Astronomical Union](/source/International_Astronomical_Union) (IAU). Since 1946, the IAU has delegated this task to the [Sternberg Astronomical Institute](/source/Sternberg_Astronomical_Institute) and the [Institute of Astronomy of the Russian Academy of Sciences](/source/Institute_of_Astronomy_of_the_Russian_Academy_of_Sciences) in Moscow, Russia.<ref name=Griffin_2015/> Sternberg publishes the ''General Catalog of Variable Stars'' ({{sc|GCVS}}), which is amended approximately once every two years by the publication of a new ''Name-List of Variable Stars''.<ref name=sternberg/> For example, in December&nbsp;2011, the 80th ''Name-List of Variable Stars'', Part&nbsp;II, was released, containing designations for 2,161&nbsp;recently discovered variable stars, which brought the total number in the {{sc|GCVS}} to 45,678&nbsp;variable stars. Among the newly designated objects were V0654&nbsp;Aurigae, V1367&nbsp;Centauri, and BU&nbsp;Coronae Borealis.<ref name=namelist/>

== Footnotes ==
{{notelist|199em}}

== See also ==
* [star catalogue](/source/star_catalogue)
* [star designation](/source/star_designation)

== References ==
{{reflist|25em|refs=

<ref name=cds>
{{cite report
 |title=The names and catalogues of variable stars
 | publisher = [University of Strasbourg](/source/University_of_Strasbourg)
 | place = Strasbourg, FR
 |url=http://cdsarc.u-strasbg.fr/afoev/var/edenom.htx
 |via=cdsarc.u-strasbg.fr
 |access-date=2018-11-16
}}
</ref>

<ref name=chapman>
{{cite journal
 |last=Chapman |first=David M.F.
 |year=1999
 |title=Reflections: F.W.A. Argelander - ''Star Charts and Variable Stars''
 |journal=[Journal of the Royal Astronomical Society of Canada](/source/Journal_of_the_Royal_Astronomical_Society_of_Canada)
 |volume=93 |pages=17
 |bibcode=1999JRASC..93...17C
}}
</ref>

<ref name=coelum>
{{cite book
 |first=Nicolas-Louis |last=de la Caille |author-link=Nicolas-Louis de Lacaille
 |year=1763
 |title=Coelum australe stelliferum
 |publisher=Hipp. Lud.Guerin & Lud. Fr. Delatour
 |bibcode=1763cas..book.....D |url=https://books.google.com/books?id=ijEVAAAAQAAJ
 |via=Google
}}
</ref>

<ref name=levy>
 {{cite book
 |first=D.H. |last=Levy |author-link=David H. Levy
 |date=15 December 2005
 |title=''David Levy's'' Guide to Variable Stars
 |publisher=Cambridge University Press
 |isbn=978-0-521-60860-2
 |page=46&nbsp;ff
 |url=https://books.google.com/books?id=Df9d8FBagqEC&pg=PA46
}}
</ref>

<ref name=namelist>
{{cite journal
 |first1 = E.V. |last1 = Kazarovets
 |first2 = N.N. |last2 = Samus
 |first3 = O.V. |last3 = Durlevich
 |first4 = N.N. |last4 = Kireeva
 |first5 = E.N. |last5 = Pastukhova 
 |collaboration = GCVS Research Group
 |display-authors = etal
 |year=2013
 |title=Novae in the 80th ''Name-list of Variable Stars'' (Part 3): Official announcement of GCVS names
 |journal=Peremennye Zvezdy 
 |trans-journal=Variable Stars
 |volume=33 |issue=3 |pages=3
 |bibcode=2013PZ.....33....3K
 |issn=2221-0474
}}
</ref>

<ref name=sternberg>
{{cite web
 |first1 = N.N. |last1 = Samus
 |first2 = E.V. |last2 = Kazarovets
 |first3 = O.V. |last3 = Durlevich
 |first4 = N.N. |last4 = Kireeva
 |first5 = E.N. |last5 = Pastukhova 
 |collaboration = GCVS Research Group
 |display-authors = etal
 |date = c. 1998
<!-- moved into author list ---
 |editor-last = Durlevich  |editor-first = Olga
-->
 |title = GCVS Research Group: History and persons
 |publisher = [Sternberg Astronomical Institute](/source/Sternberg_Astronomical_Institute) 
 |place = Moscow, RU
 |quote = International service of variable stars: Naming, classification, identification
 |url = http://www.sai.msu.ru/gcvs/intro.htm
 |via = sai.msu.ru
 |access-date = 2018-11-16
}}
</ref>

<ref name=wagman>
{{cite book
 |first=Morton |last=Wagman
 |year=2003
 |title=Lost Stars: Lost, missing, and troublesome stars from the catalogues of Johannes Bayer, Nicholas-Louis de la Caille, John Flamsteed, and sundry others
 |pages={{mvar|viii}}, 540
 |publisher=McDonald & Woodward Publishing
 |isbn=978-0-939923-78-6
 |bibcode=2003lslm.book.....W
 |url=https://books.google.com/books?id=TYLvAAAAMAAJ
}}
</ref>

<ref name=Griffin_2015>{{cite journal
 | title=How Variable Stars get Their Names
 | last=Griffin | first=David
 | journal=British Astronomical Association Variable Star Section Circular
 | volume=163 | pages=9–10 | date=March 2015
 | bibcode=2015BAAVC.163....9G }}</ref>

<ref name=Chambers_1865>{{cite journal
 | title=A Catalogue of variable Stars
 | first=George F. | last=Chambers
 | journal=Astronomische Nachrichten
 | volume=63 | issue=7–8 | year=1865 | pages=117–124
 | doi=10.1002/asna.18650630703 }}</ref>

}} <!-- end "refs=" -->

== Further reading ==
{{refbegin|25em|small=yes}}
* {{cite report |title=General Catalogue of Variable Stars (GCVS) |last1=Samus |first1=N.N. |last2=Durlevich |first2=O.V. |year=2009 |volume=1 |bibcode=2009yCat....102025S |display-authors=etal |department=(Samus+ 2007-2013) |website=VizieR On-line Data Catalog |series=B/gcvs |type=online database}} {{nobr|Original publication {{bibcode|2009yCat....102025S}}}}

* {{cite report |url=http://cdsweb.u-strasbg.fr/afoev/var/edenom.htx |title=The names and catalogues of variable stars |last=Schweitzer |first=Emile |publisher=[University of Strasbourg](/source/University_of_Strasbourg) |access-date=2005-11-06 |via=cdsweb.u-strasbg.fr |series=Les étoiles variables [The variable stars] |translator-first=Jacques |translator-last=Vialle}}
{{refend}}

designation
Category:Stellar astronomy
Category:Objects with variable star designations

---
Adapted from the Wikipedia article [Variable-star designation](https://en.wikipedia.org/wiki/Variable-star_designation) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Variable-star_designation?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.