Bayer designation

BayerdesignationdesignationsBayer letteralphaalpha starBayer naming systemBayer star designationBayer star designationsBayer's designations
A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name.wikipedia
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Aldebaran

Alpha Tauribrightest starRohini
(See 88 modern constellations for the genitive forms.) For example, Aldebaran in the constellation Taurus (the Bull) is designated α Tauri (pronounced Alpha Tauri), which means "Alpha of the Bull".
α Tauri is the star's Bayer designation.

HD 117440

d Cend Centauri
Examples include s Carinae (s of the constellation Carina), d Centauri (d of the constellation Centaurus), G Scorpii (G of the constellation Scorpius), and N Velorum (N of the constellation Vela).
HD 117440, also known by its Bayer designation d Centauri (d Cen), is a binary star in the constellation Centaurus.

Puppis

ζ-PuppisPuppusPup
(Constellations with no alpha include Vela and Puppis – both formerly part of Argo Navis, whose alpha is Canopus in Carina.)
Despite the division, Lacaille kept a single set of Bayer designations for the whole constellation Argo.

Rigel

β Ori (Rigel)B2 IaeBeta Orionis
Beta Orionis is the star's Bayer designation.

Betelgeuse

α OriBetelg'''euseBetelgeuse mass loss
α Orionis (Latinised to Alpha Orionis) is the star's Bayer designation.

Vela (constellation)

VelaFalse Crossconstellation Vela
Examples include s Carinae (s of the constellation Carina), d Centauri (d of the constellation Centaurus), G Scorpii (G of the constellation Scorpius), and N Velorum (N of the constellation Vela). (Constellations with no alpha include Vela and Puppis – both formerly part of Argo Navis, whose alpha is Canopus in Carina.)
German cartographer Johann Bayer depicted the constellation on his Uranometria of 1603, and gave the stars Bayer designations from Alpha to Omega.

G Scorpii

G ScoG Sco (Fuyue)
Examples include s Carinae (s of the constellation Carina), d Centauri (d of the constellation Centaurus), G Scorpii (G of the constellation Scorpius), and N Velorum (N of the constellation Vela).
G Scorpii is the star's Bayer designation.

Centaurus

Cena picture of himselfCentaur
Examples include s Carinae (s of the constellation Carina), d Centauri (d of the constellation Centaurus), G Scorpii (G of the constellation Scorpius), and N Velorum (N of the constellation Vela).
It is also the only globular cluster to be designated with a Bayer letter; the globular cluster 47 Tucanae is the only one designated with a Flamsteed number.

Mintaka

δ OriMintaka ABδ Ori (Mintaka)
Delta Orionis is the star's Bayer designation, 34 Orionis its Flamsteed designation.

Thuban

α DraconisAdibAlpha Draconians
Although the brightest star in Draco is Eltanin (Gamma Draconis), Thuban was assigned alpha by Bayer because, due to precession, Thuban was the north pole star 4,000 years ago.
α Draconis (Latinised to Alpha Draconis) is the star's Bayer designation.

P Cygni

P CygP Cygni profileP-Cygni Profile
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. The Latin-letter designations are not as commonly used as the Greek-letter ones (especially in constellations with Flamsteed designations), but there are some exceptions such as h Persei (which is actually a star cluster) and P Cygni.
The designation "P" was originally assigned by Johann Bayer in Uranometria as a nova.

Gemini (constellation)

Geminiconstellation GeminiGem
Castor and Pollux of Gemini may be an example of this: Pollux is brighter than Castor, but the latter rises earlier and was assigned alpha.
Castor's Bayer designation as "Alpha" arose because Johann Bayer did not carefully distinguish which of the two was the brighter when he assigned his eponymous designations in 1603.

Gemini (constellation)

Geminiconstellation GeminiGem
Castor and Pollux of Gemini may be an example of this: Pollux is brighter than Castor, but the latter rises earlier and was assigned alpha.
Castor's Bayer designation as "Alpha" arose because Johann Bayer did not carefully distinguish which of the two was the brighter when he assigned his eponymous designations in 1603.

Pollux (star)

Polluxβ Gemβ Geminorum
Castor and Pollux of Gemini may be an example of this: Pollux is brighter than Castor, but the latter rises earlier and was assigned alpha.
β Geminorum (Latinised to Beta Geminorum) is the star's Bayer designation.

Upsilon Librae

υ Lib
Bayer's Gamma and Omicron Scorpii, for example, were later reassigned from Scorpius to Libra and given the new names Sigma and Upsilon Librae.
Upsilon Librae (υ Lib, υ Librae) is the Bayer designation for a double star in the zodiac constellation Libra.

Sirius

SothisDog StarSirius B
The Greek letter names are sometimes written out as well: Alpha Canis Majoris, Beta Persei.
The system has the Bayer designation α (Alpha) Canis Majoris.

Rho Aquilae

ρ Aqlρ Aquilaeρ Aql (Tso Ke)
The proper motion of Rho Aquilae, for example, carried it across the boundary into Delphinus in 1992.
Rho Aquilae, ρ Aquilae, is the Bayer designation for a star in the northern constellation of Delphinus.

Pi2 Orionis

π 2 Oriπ 2 π2 Ori
Usually these are double stars (mostly optical doubles rather than true binary stars), but there are some exceptions such as the chain of stars π 1, π 2, π 3, π 4, π 5 and π 6 Orionis.
Pi 2 Orionis (π 2 Ori, π 2 Orionis) is the Bayer designation for a solitary star in the equatorial constellation of Orion.

Fomalhaut

Alpha Piscis AustriniFomalhaut (α PsA)Fomalhaut A
(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.
α Piscis Austrini (Latinised to Alpha Piscis Austrini) is the system's Bayer designation.

Table of stars with Bayer designations

Table of stars with Bayer designations
This table lists those stars or other objects which have Bayer designations by the constellation in which those stars or objects lie.

Variable star designation

designationvariable star designationsAG Piscium
Uppercase Latin Bayer designations in modern use do not go beyond Q; names such as R Leporis and W Ursae Majoris are variable star designations, not Bayer designations.
It uses a variation on the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in which the star lies.

Flamsteed designation

designationFlamsteedcatalogue of stars
The Latin-letter designations are not as commonly used as the Greek-letter ones (especially in constellations with Flamsteed designations), but there are some exceptions such as h Persei (which is actually a star cluster) and P Cygni.
Flamsteed designations for stars are similar to Bayer designations, except that they use numbers instead of Greek and Roman letters.

Cygnus (constellation)

Cygnusconstellation of CygnusCygnus constellation
In 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 catalogued many stars in the constellation, giving them the Bayer designations from Alpha to Omega and then using lowercase Roman letters to g. John Flamsteed added the Roman letters h, i, k, l and m (these stars were considered informes by Bayer as they lay outside the asterism of Cygnus), but were dropped by Francis Baily.

Johann Bayer

Bayer Johann BayerBayer, Johann
Most of the brighter stars were assigned their first systematic names by the German astronomer Johann Bayer in 1603, in his star atlas Uranometria.
The Uranometria introduced a new system of star designation which has become known as the Bayer designation.

Genitive case

genitivegen.GEN
A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name.
Names of astronomical constellations are Latin, and the genitives of their names are used in naming objects in those constellations, as in the Bayer designation of stars. For example, the brightest star in the constellation Virgo is called Alpha Virginis, which is to say "Alpha of Virgo", as virginis is the genitive of virgō. Note that plural forms and adjectives also decline accordingly: plural Alpha Piscium (Pisces) and Alpha Canum Venaticorum (Canes Venatici) versus singular Alpha Piscis Austrini (Piscis Austrinus) and Alpha Canis Majoris (Canis Major). Astronomy manuals often list the genitive forms, as some are easy to get wrong even with a basic knowledge of Latin, e.g. Vela, which is a neuter plural not a feminine singular: Delta Velorum not *Delta Velae.