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Star names: history

by Marion Schmitz, Chair of IAU Working Group on Designations

Historically, the brightest stars were named by ancient cultures with names that had special meaning for them. A good book describing the history of star names is R.H. Allen's "Star-Names and their Meanings" (G.E. Stechert, New York, 1899) - which has also become a Dover reprint as "Star Names: Their Lore and Meanings". This is a fantastic book on the subject. A fun little WWW site giving the meaning of some star names can be found at: http://www.ras.ucalgary.ca/~gibson/starnames/starnames.html

As astronomy progressed, a need arose to be more systematic in the cataloging of stars and several systems were set up which were made up of the constellation within which a star resided. One system (Bayer's) arranged the stars in order of brightness and gave the brightest star the highest letter of the Greek alphabet, alpha. The next brightest was beta, etc. Another system (Flamsteed's) assigned Latin numbers to the stars, although the brightest star was NOT number "1". Thus, you might see star names such as alpha Centauri or 54 Cancri.

The above worked well for the "naked-eye" stars and are pretty much contained in the Yale Bright Star Catalog (BS) which is comparable to the Harvard Revised (HR) catalog of bright stars. These catalogs were ordered by coordinates on the sky (R.A. and Dec.) and astronomers still use these catalog numbers quite regularly (e.g. HR 1099).

As telescopes began detecting fainter and fainter stars, more catalogs were produced which tried to document special features about the stars. The Henry Draper (HD) catalog used a sequential numbering system for the hundreds of thousands of stars ordered by RA and Dec and included spectral types for the stars. The Durchmusterung series (BD, CD, CPD, SD) also cataloged hundreds of thousands of stars, but used a different naming system. The star name was made up of the Declination zone to which a star belonged followed by a sequential number of the star within that zone. For example, BD+45 4576.

Certainly, none of the catalogs above wanted to miss the brighter stars that were in the earlier catalogs, but they also wanted to keep the specialized numbering system they devised, so there is considerable overlap of the same stars among the different catalogs. These are known as cross-identifications. For example, the brightest star in the sky is known as (according to SIMBAD):
Sirius = alpha CMa = 9 CMa = HR 2491 = HD 48915 = BD-16 1591

Modern catalogs basically use one of two styles of designation - sequential number or coordinate-based. The sequential number system generally starts at "1" (although some astronomers like to start at "0"), and progress until the last object in their list which would have the highest number. Coordinate- based names generally use the R.A. and Dec. of a star as the name. When a coordinate-based system is used, however, it must be made clear which epoch (year) was used when computing the coordinates. Due to the Earth's precession, and space motion of a star itself, the coordinates of the star in 1950 were very different than those in 2000. The most common systems in use are the Besselian 1950 and the Julian 2000 systems. By convention, star names based on J2000 coordinates contain the letter "J" in front of the coordinate. Using Sirius as an example again, we have modern catalog names of
Sirius = HIC 32349 = CCDM J06451-1643
These are the Hipparcus Input Catalog (HIC) and the Catalog of Components of Double and Multiple star systems (CCDM).

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Posted 21 September 2004