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Star Catalogue

Star Catalogue — In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, and this article covers only some of the more frequently quoted ones.

Most of the recent catalogues are available in electronic format and can be freely downloaded from NASA’s Astronomical Data Center and other places (see links at end).

Historical Catalogues

Although no longer in serious use, mention should be made of Ptolemy’s star catalogue published in the 2nd century as part of his Almagest, which lists 1022 stars visible from Alexandria and was the standard star catalogue in the Western and Arab worlds for over a thousand years.

Ptolemy’s catalogue was based to some extent on an earlier one by Hipparchus from the 2nd century B.C. An even earlier star catalogue was that of Timocharis of Alexandria, which was written about 300 B.C. and later used by Hipparchus.

Two system introduced in historical catalogues remain in use to the present day. Those of Bayer’s Uranometria are for bright stars, and these are given a Greek letter followed by the genitive case of the constellation in which they are located; examples are Alpha Centauri or Gamma Cygni. See Bayer designation for more information.

The major problem with Bayer’s naming system was the number of letters in the Greek alphabet. It was easy to run out of letters before running out of stars needing names. Following up on Bayer was John Flamsteed introduced another system in Historia coelestis Britannica who kept the genitive-of-the-constellation rule for the back end of his catalog names, but used numbers instead of the Greek alphabet for the front half. Examples include 61 Cygni and 47 Ursae Majoris; see Flamsteed designation for more information.

Full-Sky Catalogues

Bayer and Flamsteed covered only a few thousand stars between them. In theory, full-sky catalogues try to list every other star in the sky. There are, however, literally hundreds of millions, even billions of stars resolvable by telescopes, so this is an impossible goal; these kind of catalogs generally try to get every star brighter than a given magnitude.

HD / HDE

The Henry Draper Catalogue was published in the period 1918-1924. It covers the whole sky down to about ninth or tenth magnitude, and is notable as the first large-scale attempt to catalogue spectral types of stars. The catalogue was compiled by Annie Cannon and her co-workers at Harvard College Observatory under the supervision of Edward Pickering, and was named in honour of Henry Draper, whose widow donated the money required to finance it.

HD numbers are widely used today for stars which have no Bayer or Flamsteed designation. Stars numbered 1-225300 are from the original catalogue and are numbered in order of right ascension for 1900.0 epoch. Stars in the range 225301-359083 are from the 1949 extension of the catalogue. The notation HDE is used only for stars in this extension, but even these are usually denoted HD as the numbering ensures that there can be no ambiguity.

SAO

The Smithsonian Astrophysical Observatory catalogue is a photographic atlas of the sky, complete to about ninth magnitude, as a result of which there is considerable overlap with the Henry Draper catalogue. The epoch for the position measurements in the latest edition is J2000.0.

The SAO catalogue contains one more major piece of information than Draper, the proper motion of the stars, so is often used when that fact is of importance. The cross-references with the Draper and Durchmusterung catalogue numbers in the latest edition are also useful.

Names in the SAO catalogue start with the letters SAO, followed by a number. The numbers are assigned following 18 ten-degree bands in the sky, with stars sorted by right ascension within each band.

BD/CD/CPD

The Bonner Durchmusterung and followups were the most complete of the pre-photographic star catalogues.

The Bonner Durchmusterung itself was published by Friedrich Wilhelm Argelander, Adalbert Krger, and Eduard Schnfeld between 1852 and 1859. It covered 320,000 stars in epoch 1855.0.

As it covered only the northern sky and some of the south, this was then supplemented by the Southern Durchmusterung (1886, 120,000 stars), which was then supplemented by the Cordoba Durchmusterung (580,000 stars), which ran through the south in 1892. This in turn was supplemented by the Cape Photographic Durchmusterung (450,000 stars, 1896).

Astronomers preferentially use the HD designation of a star, as that catalogue also gives spectroscopic information, but as the Durchmusterungs cover more stars they occasionally fall back on the older designations when dealing with one not found in Draper.

Star names from these catalogues include the initials of which of the four catalogues they are from (though the Southern follows the example of the Bonner and uses BD), followed by the angle of declination of the star, followed by an arbitrary number as there are always thousands of stars at each angle. Examples include BD+501725 or CD-4513677.

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Star Catalogue


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