Popular Star Names
The brightest stars in the sky are known by their popular names, such as Sirius, Canopus, Rigel Kentaurus, Arcturus, Vega, Capella, Rigel, Procyon, Betelgeuse, and Archenar.
Many other stars also have popular names, but sometimes these stars have multiple names derived from different traditions, cultures, and mythologies.
Bayer Star Designations
In 1603 Johannes Bayer attempted to bring more order to the names of stars by using lower case Greek letters in his star atlas Uranometria.
Bayer used lower-case Greek letters followed by the Latin genitive (possessive) form of the constellation's name. For example, Rigel, the brightest star in the constellation of Orion, is designated as β Ori (Beta Orionis).
He usually used the first letter of the Greek alphabet, Alpha, to designate the brightest star in a constellation, and Beta as the second brightest and so on. But, not in every case, so the brightest star in a constellation was not always assigned the alpha designation.
The Greek alphabet has 24 letters. For constellations with more than 24 Bayer-designated stars, Bayer then used lower-case Roman letters, and when those ran out, he used upper-case Roman letters. In his atlas, he only had to use up to the upper-case Roman letter Q.
Now the upper-case Roman letters after Q are reserved for variable stars. After these single letters were used for variables, double letters like AA, AB, AC, AD, etc. were used. After these combinations were used up, the upper-case Roman letter V was used combined with a number starting with 335 for the rest of the variable stars.
Today, Bayer designations are still primarily used to identify the brightest stars in constellations and are used in the constellation image maps in this book.
The Greek Alphabet's Lower Case Letters
Flamsteed Star Numbers
In the late 1600's and 1700's, John Flamsteed accurately cataloged a large number of stars with the aid of a telescope. This work was published posthumously in 1725 in a catalog of stars called Historia Coelestis Britannica. He used Bayer and Roman letters for star designations. He did not use any numerals for identifying the stars.
The French astronomer Joseph Jérôme Lefrançois de Lalande added numbers for star designations in a revised edition of Flamsteed's catalog that was published in a French almanac in 1783. He numbered the stars consecutively by constellation in order of increasing right ascension.
These numbered stars are now called "Flamsteed numbers", even though Flamsteed did not use them. Flamsteed designations are similar to Bayer designations. They use a number followed by the Latin genitive of the constellation name. Flamsteed designations, such as 51 Pegasi and 61 Cygni are now commonly used for stars where no Bayer designation exists.
However, since constellation boundaries were not formalized by the International Astronomical Union (IAU) until 1930, and because of the effects of precession, some stars with Flamsteed numbers now lie in different constellations than they did originally.
Other Star Catalogs
Early star atlases and catalogs were limited in their magnitudes. Subsequent works over the years have substantially improved the number of stars listed and their positions.
The Bonner Durchmusterung (BD) catalog was an astrometric star catalog that was compiled by the Bonn Observatory in Germany from 1859 to 1903. It cataloged stars down to about 10th magnitude.
The Henry Draper (HD) catalog was another catalog specially created between 1918 and 1924 to list the spectral classes of stars down to about 10th magnitude.
The Smithsonian Astrophysical Observatory (SAO) catalog was created in 1966 from previous astrometric catalogs and contains only stars whose proper motions were known down to about 9th magnitude.
The United States Naval Observatory (UNSO) created an all-sky catalog with accurate positions, proper motions and magnitudes for more than one billion objects from scans of photographic plates taken with Schmidt cameras. The UNSO-B1.0 catalog goes down to a V magnitude of 21.
The UNSO also maintains the Washington Double Star catalog. It is the "world's principal database of astrometric double and multiple star information."
The Hubble Space Telescope Guide Star Catalog (GSC) was created in the late 1980's to provide accurate positions of stars for use as guide stars for the Hubble Space Telescope. It contained about 20 million stars between magnitudes 6 and 15. The latest version contains information on nearly 1 billion stars down to magnitude 21.
The Hipparcos (HIP) catalog was created from measurements taken by the Hipparcos satellite in the 1990's. It measured accurate parallaxes of nearby stars to determine their distances.
The United States Naval Observatory CCD Astrographic Catalog (UCAC2) is a high-accuracy astrometric catalog of 48,366,996 stars covering the sky completely from -90 to +40 degrees in declination with proper motions, positions, and photometry information for all stars in the catalog.
The Tycho-2 catalog is an astrometric and photometric reference catalogue of 2.5 million of the brightest stars covering the entire sky based on observations by the Hipparcos satellite.
The Naval Observatory Merged Astrometric Dataset (NOMAD) has merged data from Hipparcos, Tycho-2, UCAC-2 and UNSO-B1 and 2MASS catalogs.
Today a star will be listed in multiple catalogs and have multiple designations. These can be found by looking up a star in SIMBAD. For example, Vega, has the following designations, among others:
- Alpha Lyrae
- BD+38 3238
- HD 172167
- HIP 91262
- SAO 67174
- TYC 3105-2070-1
- USNO-B1.0 1287-00305764
SIMBAD is an acronym for:
Set of Identifications, Measurements and Bibliography for Astronomical Data.
The SIMBAD database was developed, and is managed by, the Centre de Données astronomiques de Strasbourg (CDS) in Strasbourg, France.