The Naming of Stars
Astronomers use a number of conventions to name stars. Most conventions
have their origins hundreds of years ago. All star names and designations must
be approved by the International Astronomical
Union. The Centre de Données
astronomiques de Strasbourg (CDS) provides a
Dictionary of Nomenclature of
The following are some standard nomenclatures for stars.
The arabic, Bayer, and Flamsteed designations exist only for the very
brightest, visible. stars in the sky.
Most stars are known by catalog names. Common star catalogs include:
- Arabic names, e.g., Aldebaran or Betelgeuse, have a
lot of lore behind them. You can learn about their origins and meanings
in Allen's "Star Names and their Meanings".
- Bayer designations order the stars in a given constellations from the
brightest on down. The stars are in (Greek) alphabetical order. The brightest
stars in the constellation Orion are
also known as Betegeuse. The second brightest is
- Flamsteed designations are ordered by
ascension. These designations are numerical. The westernmost star in Taurus
is 1 Tau, the next is 2 Tau, etc.
- the Yale Catalog of Bright Stars.
Stars in this catalog are designated as
HRxxxx or BSxxxx. There are 9110 entries in this catalog,
which includes most stars brighter than visual magnitude 6.5. This catalog
contains much supplementary information about these stars.
- The Henry Draper Catalog (HDxxxxxx) contains positions,
spectral types, and magnitudes of about 225,000 stars (plus more in
supplements) to about ninth magnitude.
- The Durchmusterung catalogs (BD, CoD, CPD),
(DMsdd xxxx, where
sdd is the declination and xxxx is the
running number in that declination band, beginning at 0 hours
- The SAO catalog (SAOxxxxxx) is a positional catalog of about
250,000 stars to about tenth magnitude.
- The Hubble Space Telescope Guide Star Catalog (GSCxxxx yyyy)
contains positions of stars to magnitude 16.
Most bright stars have many names. Betelgeuse is also known as
58 Ori, BD+7 1055, HR2061, HD39801, and SAO113271. There are other
names too, including entries in double star and variable star catalogs.
Variable stars are named by constellation, and in the order that they are
identified. The first
variable star in a constellation is called R (e.g., R Mon),
the second S,
and so on through Z. That works for 9 stars. The next set uses two
letter designations, beginning with
RR, followed by RS through RZ, then SS through
SZ and so on to ZZ. Then one goes to AA ... AZ,
BB ... BZ ... QZ. This can account for 334 variable
stars in a constellation. Since there are often many more than this,
variable stars after QZ are designated as V followed by the number
The variable star after QZ Tau is V335 Tau. There are over
2000 variable stars catalogued in Sagittarius alone!
Bright stars, even if variable, do not get variable star names. The
eclipsing variable Algol goes by its Bayer designation,
the Catalog of Variable Stars.