PPM Star Catalogue
Encyclopedia
The PPM Star Catalogue is the successor of the SAO Catalogue
. It contains precise positions and proper motions of 378,910 star
s on the whole sky in the J2000/FK5 coordinate system.
It is designed to represent as closely as possible the IAU
(1976) coordinate system on the sky, as defined by the FK5 star catalogue
. Thus, the PPM is an extension of the FK5 system to higher star densities and fainter magnitudes.
While the SAO catalog is more or less complete to V=9, with 4,503 stars fainter than V=10, the PPM catalog is fairly complete to V=9.5, with 102,672 stars fainter than V=10 and 22,395 stars fainter than V=11. Released after the original PPM, the PPM supplemental list was intended to render the PPM complete to magnitude V=7.5. For fainter magnitudes, the supplemental list documentation states that,
... of the perhaps 20,000 stars between V=7.5 and V=8.5 only a few hundred are missing from PPM. So, the combined PPM can be considered as practically complete to at least V=8.5. In photographic magnitudes this corresponds to roughly 9 mag.
The data contained in the catalogue is downloadable from NASA
(and other sites). The four files of the catalog are PPM North, PPM South, Bright Star Supplement to PPM, and The 90000 stars Supplement to the PPM Catalogue.
Smithsonian Astrophysical Observatory Star Catalog
The Smithsonian Astrophysical Observatory Star Catalog is an astrometric star catalogue. It was published by the Smithsonian Astrophysical Observatory in 1966 and contains 258,997 stars. The catalogue was...
. It contains precise positions and proper motions of 378,910 star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s on the whole sky in the J2000/FK5 coordinate system.
It is designed to represent as closely as possible the IAU
IAU
IAU may refer to:*International Astronomical Union*International American University*International American University College of Medicine*International Association of Universities*International Association of Ultrarunners...
(1976) coordinate system on the sky, as defined by the FK5 star catalogue
Star catalogue
A star catalogue, or star catalog, is an astronomical catalogue that lists stars. 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...
. Thus, the PPM is an extension of the FK5 system to higher star densities and fainter magnitudes.
Description
The PPM can be considered a replacement of two preceding astrometric catalogs which served a similar purpose: AGK3 and the SAO Catalog. In contrast to the PPM, these older catalogs are based on (1) the now obsolete FK4 system of positions and proper motions, and (2) only two position measures per star.While the SAO catalog is more or less complete to V=9, with 4,503 stars fainter than V=10, the PPM catalog is fairly complete to V=9.5, with 102,672 stars fainter than V=10 and 22,395 stars fainter than V=11. Released after the original PPM, the PPM supplemental list was intended to render the PPM complete to magnitude V=7.5. For fainter magnitudes, the supplemental list documentation states that,
... of the perhaps 20,000 stars between V=7.5 and V=8.5 only a few hundred are missing from PPM. So, the combined PPM can be considered as practically complete to at least V=8.5. In photographic magnitudes this corresponds to roughly 9 mag.
The data contained in the catalogue is downloadable from NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
(and other sites). The four files of the catalog are PPM North, PPM South, Bright Star Supplement to PPM, and The 90000 stars Supplement to the PPM Catalogue.