Editing Bayer designation

{{short description|Star naming system}}
[[File:Bayer Designation orion.jpg|thumb|Detail of Bayer's chart for [[Orion (constellation)|Orion]] showing the [[Orion's Belt|belt stars]] and [[Orion Nebula]] region, with both Greek and Latin letter labels visible]]
A '''Bayer designation''' is a [[stellar designation]] in which a specific [[star]] is identified by a [[Greek alphabet|Greek]] or [[Latin]] letter followed by the [[genitive case|genitive]] form of its parent constellation's Latin name. The original list of Bayer designations contained 1564 stars. The brighter stars were assigned their first systematic names by the German [[astronomer]] [[Johann Bayer]] in 1603, in his star atlas ''[[Uranometria]]''. Bayer catalogued only a few stars too far south to be seen from Germany, but later astronomers (including [[Nicolas-Louis de Lacaille]] and [[Benjamin Apthorp Gould]]) supplemented Bayer's catalog with entries for southern constellations.

==Scheme==
Bayer assigned a lowercase [[Greek alphabet|Greek letter]] (alpha (α), beta (β), gamma (γ), etc.) or a Latin letter (A, b, c, etc.) to each star he catalogued, combined with the Latin name of the star's parent constellation in [[genitive case|genitive]] (possessive) form. The constellation name is frequently abbreviated to a standard three-letter form.<ref>{{cite book |author1=Rabinowitz, Harold |author2=Vogel, Suzanne |title=The Manual of Scientific Style: A Guide for Authors, Editors, and Researchers |url=https://books.google.com/books?id=YZCqJzffR20C&pg=PA363 |date=12 June 2009 |publisher=Elsevier |isbn=978-0-08-055796-0 |pages=363ff}}</ref>{{efn|See the article ''[[88 modern constellations]]'' for a list of the genitive forms and the constellations' standard abbreviations.}} For example, [[Aldebaran]] in the constellation [[Taurus (constellation)|Taurus]] (the Bull) is designated ''α&nbsp;Tauri'' (abbreviated ''α&nbsp;Tau'', pronounced ''Alpha Tauri''), which means "Alpha of the Bull".{{efn|The letters of the Greek alphabet were [[Greek numerals|used in antiquity as numerals]], however in a different way.}}<ref>{{cite book |first=Johann |last=Bayer |title=Uranometria |publisher=Archival Facsimiles |year=1987 |isbn=1852970219}}</ref>

Bayer used Greek letters for the brighter stars, but the Greek alphabet has only twenty-four letters, while a single constellation may contain fifty or more stars visible to the naked eye. When the Greek letters ran out, Bayer continued with Latin letters: uppercase ''A'', followed by lowercase ''b'' through ''z'' (omitting ''j'' and ''v'', but ''o'' was included), for a total of another 24&nbsp;letters.<ref name="Ridpath">{{cite book |first=Ian |last=Ridpath |title=Star Tales |chapter=Bayer's ''Uranometria'' and Bayer letters |publisher=Lutterworth Press |year=1989 |isbn=0718826957 |url=http://www.ianridpath.com/startales/bayer.html}}</ref>

Bayer did not label "permanent" stars with uppercase letters (except for ''A'', which he used instead of ''a'' to avoid confusion with ''α''). However, a number of stars in southern constellations have uppercase letter designations, like [[HD 102964|B Centauri]] and [[G Scorpii]]. These letters were assigned by later astronomers, notably Lacaille in his ''Coelum Australe Stelliferum'' and Gould in his ''Uranometria Argentina''. Lacaille followed Bayer's use of Greek letters, but this was insufficient for many constellations. He used first the lowercase letters, starting with ''a'', and if needed the uppercase letters, starting with ''A'', thus deviating somewhat from Bayer's practice. Lacaille used the Latin alphabet three times over in the large constellation [[Argo Navis]], once for each of the three areas that are now the constellations of [[Carina (constellation)|Carina]], [[Puppis]] and [[Vela (constellation)|Vela]]. That was still insufficient for the number of stars, so he also used uppercase Latin letters such as [[HD 82668|N&nbsp;Velorum]] and [[Q Puppis]]. Lacaille assigned uppercase letters between R and Z in several constellations, but these have either been dropped to allow the assignment of those letters to variable stars or have actually turned out to be variable.<ref>{{cite book |title=Coelum australe stelliferum&nbsp;... |url=https://books.google.com/books?id=LIo_AAAAcAAJ&pg=PP7 |year=1763 |publisher=H.L. Guerin & L.F. Delatour |pages=7ff |via=Google Books}}</ref>

== Order by magnitude class ==

In most constellations, Bayer assigned Greek and Latin letters to stars within a constellation in rough order of [[apparent magnitude|apparent brightness]], from brightest to dimmest.  The order is not necessarily a precise labeling from brightest to dimmest: in Bayer's day stellar brightness could not be measured precisely. Instead, stars were traditionally assigned to one of six magnitude classes (the brightest to first magnitude, the dimmest to sixth), and Bayer typically ordered stars within a constellation by class: all the first-magnitude stars (in some order), followed by all the second-magnitude stars, and so on. Within each magnitude class, Bayer made no attempt to arrange stars by relative brightness.<ref name=jha17_50_189>{{cite journal | title=A Star Catalogue Used by Johannes Bayer | last=Swerdlow | first=N. M. | journal=Journal for the History of Astronomy | volume=17 | issue=50 | pages=189–197 |date=August 1986 | bibcode=1986JHA....17..189S | doi=10.1177/002182868601700304 | s2cid=118829690 }} See p. 192.</ref> As a result, the brightest star in each class did not always get listed first in Bayer's order—and the brightest star overall did not necessarily get the designation "Alpha".  A good example is the constellation [[List of stars in Gemini|Gemini]], where [[Pollux (star)|Pollux]] is Beta Geminorum and the slightly dimmer [[Castor (star)|Castor]] is Alpha Geminorum.

In addition, Bayer did not always follow the magnitude class rule; he sometimes assigned letters to stars according to their location within a constellation, or the order of their rising, or to historical or mythological details. Occasionally the order looks quite arbitrary.<ref name="Ridpath"/>

Of the 88 modern constellations, there are at least 30 in which Alpha is not the brightest star, and four of those lack a star labeled "Alpha" altogether. The constellations with no Alpha-designated star include [[Vela (constellation)|Vela]] and [[Puppis]]—both formerly part of [[Argo Navis]], whose Greek-letter stars were split among three constellations. [[Canopus]], the former α Argus, is now α Carinae in the modern constellation [[Carina (constellation)|Carina]]. [[Norma (constellation)|Norma's]] Alpha and Beta were reassigned to [[Scorpius]] and re-designated [[N Scorpii|N]] and [[H Scorpii]] respectively, leaving Norma with no Alpha. [[Francis Baily]] died before designating an Alpha in [[Leo Minor]], so it also has no Alpha. (The star [[46 Leonis Minoris]] would have been the obvious candidate.)

==Orion as an example==
In [[Orion (constellation)|Orion]], Bayer first designated [[Betelgeuse]] and [[Rigel]], the two 1st-magnitude stars (those of magnitude 1.5 or less), as Alpha and Beta from north to south, with Betelgeuse (the shoulder) coming ahead of Rigel (the foot), even though the latter is usually the brighter. (Betelgeuse is a variable star and can at its maximum occasionally outshine Rigel.)<ref>{{cite book|author=Patrick Moore|title=Brilliant Stars|url=https://books.google.com/books?id=uWEOGwAACAAJ|year=1996|publisher=Cassell|isbn=978-0-304-34903-6}}</ref> Bayer then repeated the procedure for the stars of the 2nd magnitude, labeling them from ''gamma'' through ''zeta'' in "top-down" (north-to-south) order. Letters as far as Latin ''p'' were used for stars of the sixth magnitude.
[[Image:Orion constellation map.svg|upright=1.4|right|thumb|[[Orion (constellation)|Orion]] constellation map]]
{| class="wikitable"
|+ {{nowrap|Bayer's brightest three classes of stars in Orion}}
! Bayer<br/>Designation || Bayer's class || Apparent<br/>Magnitude || Proper<br/>Name 
|-
| [[α Orionis]]
| First
| 0.45
| Betelgeuse
|-
| [[β Orionis]]
| First
| 0.18
| Rigel
|-
| [[γ Orionis]]
| Second
| 1.64
| Bellatrix
|-
| [[δ Orionis]]
| Second
| 2.23
| Mintaka
|-
| [[ε Orionis]]
| Second
| 1.69
| Alnilam
|-
| [[ζ Orionis]]
| Second
| 1.70
| Alnitak
|-
| [[η Orionis]]
| Third
| 3.42
| Algjebbah
|-
| [[θ Orionis]]
| Third
|
| (Orion nebula)
|-
| [[ι Orionis]]
| Third
| 2.77
| Hatysa
|-
| [[κ Orionis]]
| Third
| 2.07
| Saiph
|}
<!--
==Various arrangements==
{{Disputed-section|date=May 2019}}
The "First to Rise in the East" order is used in a number of instances.  [[Castor (star)|Castor]] and [[Pollux (star)|Pollux]] of [[Gemini (constellation)|Gemini]] may be an example of this: Pollux is brighter than Castor, but the latter rises earlier and was assigned ''alpha''. In this case, Bayer may also have been influenced by the traditional order of the mythological names "[[Castor and Pollux]]": Castor is generally named first whenever the twins are mentioned.

Although the brightest star in Draco is Eltanin ([[Gamma Draconis]]), [[Thuban]] was assigned ''alpha'' (α) by Bayer because, due to [[precession]], Thuban was the [[pole star|north pole star]] 4,000 years ago.<ref name="MOORE">{{Cite book| title=The Observer's Year: 366 Nights in the Universe| author=Moore, Patrick| page=283| year=2005| isbn=9783540761471|url=https://books.google.com/books?id=ZnDvAAAAMAAJ&q=thuban}}</ref> Sometimes there is no apparent order, as exemplified by the stars in [[Sagittarius (constellation)|Sagittarius]], where Bayer's designations appear almost random to the modern eye. [[Alpha Sagittarii|Alpha]] and [[Beta Sagittarii]] are perhaps the most anomalously designated stars in the sky. They are more than two magnitudes fainter than the brightest star (designated [[Epsilon Sagittarii|Epsilon]]), they lie several degrees south of the main pattern (the "teapot" [[asterism (astronomy)|asterism]]), they are more than 20 degrees off the [[ecliptic]] in a [[Zodiac]]al constellation, and they do not even rise from Bayer's native Germany (while Epsilon and several other brighter stars do). The order of the letters assigned in Sagittarius does correspond to the magnitudes as illustrated on Bayer's chart; but the latter do not agree with modern determinations of the magnitudes.

Bayer designations added by later astronomers generally were ordered by magnitude, but care was usually taken to avoid conflict with designations already assigned.  In Libra, for example, the new designations sigma, tau, and upsilon were chosen to avoid conflict with Bayer's earlier designations, even though several stars with earlier letters are not as bright.
-->

== Bayer's miscellaneous labels ==

Although Bayer did not use uppercase Latin letters (except ''A'') for "fixed stars", he did use them to label other items shown on his charts, such as neighboring constellations, "temporary stars", miscellaneous astronomical objects, or reference lines like the Tropic of Cancer.<ref name="LostStars">{{cite book
 |last = Wagman
 |first = Morton
 |date = 2003
 |title = Lost Stars
 |publisher = McDonald & Woodward
 |isbn = 0939923785
}}</ref>{{rp|p. 131}} In [[Cygnus (constellation)|Cygnus]], for example, Bayer's fixed stars run through ''g'', and on this chart Bayer employs ''H'' through ''P'' as miscellaneous labels, mostly for neighboring constellations. Bayer did not intend such labels as catalog designations, but some have survived to refer to astronomical objects: [[P Cygni]] for example is still used as a designation for Nova Cyg 1600. Tycho's Star ([[SN 1572]]), another "temporary star", appears as B Cassiopeiae. In charts for constellations that did not exhaust the Greek letters, Bayer sometimes used the leftover Greek letters for miscellaneous labels as well.<ref name="LostStars"/>{{rp|p. 131}}

==Revised designations==
[[Ptolemy]] designated four stars as "border stars", each shared by two constellations: [[Alpheratz]] (in [[Andromeda (constellation)|Andromeda]] and [[Pegasus (constellation)|Pegasus]]), [[Elnath]] (in [[Taurus (constellation)|Taurus]] and [[Auriga (constellation)|Auriga]]), [[Nu Boötis]] ([[Nu1 Boötis|Nu<sup>1</sup>]] and [[Nu2 Boötis|Nu<sup>2</sup>]])(in [[Boötes]] and [[Hercules (constellation)|Hercules]]) and [[Fomalhaut]] (in [[Piscis Austrinus]] and [[Aquarius (constellation)|Aquarius]]).<ref name="LostStars"/>{{rp|p. 23}} Bayer assigned the first three of these stars a Greek letter from both constellations: {{nowrap|[[Alpha Andromedae]] {{=}} Delta Pegasi}}, {{nowrap|[[Beta Tauri]] {{=}} Gamma Aurigae}}, and {{nowrap|[[Nu Boötis]] {{=}} Psi Herculis}}. (He catalogued Fomalhaut only once, as [[Alpha Piscis Austrini]].) When the [[International Astronomical Union]] (IAU) assigned definite boundaries to the constellations in 1930, it declared that stars and other celestial objects can belong to only one constellation. Consequently, the redundant second designation in each pair above has dropped out of use.<ref name=iau2>{{cite book|author1=Eugène Delporte|author2=International Astronomical Union|title=Délimitation scientifique des constellations|url=https://books.google.com/books?id=v3XvAAAAMAAJ|year=1930|publisher=At the University press}}</ref>

Bayer assigned two stars duplicate names by mistake: {{nowrap|[[Xi Arietis]]}} (duplicated as {{nowrap|Psi Ceti}}) and {{nowrap|[[Kappa Ceti]]}} ([[Kappa1 Ceti|Kappa<sup>1</sup>]] and [[Kappa2 Ceti|Kappa<sup>2</sup>]]) (duplicated as {{nowrap|g Tauri}}). He corrected these in a later atlas, and the duplicate names were no longer used.<ref name="LostStars"/>{{rp|p. 23}}

Other cases of multiple Bayer designations arose when stars named by Bayer in one constellation were transferred by later astronomers to a different constellation. Bayer's Gamma and Omicron Scorpii, for example, were later reassigned from [[Scorpius]] to [[Libra (constellation)|Libra]] and given the new names [[Sigma Librae|Sigma]] and [[Upsilon Librae]].<ref name="LostStars"/>{{rp|p. 196}} (To add to the confusion, the star now known as [[Omicron Scorpii]] was not named by Bayer but was assigned the designation o Scorpii (Latin lowercase 'o') by Lacaille—which later astronomers misinterpreted as omicron once Bayer's omicron had been reassigned to Libra.)<ref name="LostStars"/>{{rp|p. 278}}

A few stars no longer lie (according to the modern constellation boundaries) within the constellation for which they are named. The [[proper motion]] of [[Rho Aquilae]], for example, carried it across the boundary into [[Delphinus]] in 1992.<ref name=moore>{{cite book|author=Patrick Moore|title=The Observer's Year: 366 Nights of the Universe|url=https://books.google.com/books?id=p87TBwAAQBAJ&pg=PA132|date=29 June 2013|publisher=Springer Science & Business Media|isbn=978-1-4471-3613-2|pages=132–}}</ref><ref name=hirshfeld>{{cite journal | display-authors=1 | last1=Hirshfeld | first1=A. | last2=Sinnott | first2=R. W. | last3=Ochsenbein | first3=F. | last4=Lemay | first4=D. | title=Book-Review - Sky Catalogue 2000.0 - V.1 - Stars to Magnitude 8.0 ED.2 | journal=Journal of the Royal Astronomical Society of Canada | volume=86 | issue=4 | page=221 |date=August 1992 | bibcode=1992JRASC..86..221L }}</ref>

A further complication is the use of numeric superscripts to distinguish neighboring stars that Bayer (or a later astronomer) labeled with a common letter. Usually these are [[double star]]s (mostly optical doubles rather than true [[binary star]]s), but there are some exceptions such as the chain of stars [[Pi1 Orionis|π<sup>1</sup>]], [[Pi2 Orionis|π<sup>2</sup>]], [[Pi3 Orionis|π<sup>3</sup>]], [[Pi4 Orionis|π<sup>4</sup>]], [[Pi5 Orionis|π<sup>5</sup>]] and [[Pi6 Orionis|π<sup>6</sup>]] [[Pi Orionis|Orionis]]. The most stars given the same Bayer designation but with an extra number attached to it is [[Psi Aurigae]]. ([[Psi1 Aurigae|ψ<sup>1</sup>]], [[Psi2 Aurigae|ψ<sup>2</sup>]], [[Psi3 Aurigae|ψ<sup>3</sup>]], [[Psi4 Aurigae|ψ<sup>4</sup>]], [[Psi5 Aurigae|ψ<sup>5</sup>]], [[Psi6 Aurigae|ψ<sup>6</sup>]], [[Psi7 Aurigae|ψ<sup>7</sup>]], [[Psi8 Aurigae|ψ<sup>8</sup>]], [[Psi9 Aurigae|ψ<sup>9</sup>]], [[16 Lyncis|ψ<sup>10</sup>]], although according to the modern IAU constellation boundaries, ψ<sup>10</sup> lies in [[Lynx (constellation)|Lynx]]).

==See also==
* [[Flamsteed designation]]
* [[Gould designation]]
* [[Lists of constellations]]
* [[Star catalogue]]
* [[Stellar designations and names]]
* [[Table of stars with Bayer designations]]
* [[Variable star designation]]

==References==
{{Reflist}}

==Notes==
{{notelist}}

{{DEFAULTSORT:Bayer Designation}}
[[Category:Astronomical catalogues]]
[[Category:Bayer objects|*]]