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| Alternative names | UCAC |
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The USNO CCD Astrograph Catalog (UCAC) is an astrometric star catalog of the United States Naval Observatory.
The first preliminary edition, published in March 2000, gives the positions and proper motions of over 27 million stars in the southern hemisphere in the brightness range 8–16.
The second issue was the IAU published General Assembly in Sydney (2003) and includes positions and proper motions of about 50 million stars.
The third edition was published in the IAU General Assembly in Rio (August 2009).
The fourth edition was published in August 2012.
Since Spring 2015, the successor URAT is available.
A star catalogue 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 of the more frequently quoted ones. Star catalogues were compiled by many different ancient people, including the Babylonians, Greeks, Chinese, Persians, and Arabs. They were sometimes accompanied by a star chart for illustration. Most modern catalogues are available in electronic format and can be freely downloaded from space agencies' data centres. The largest is being compiled from the spacecraft Gaia and thus far has over a billion stars.
In astronomy, stars have a variety of different stellar designations and names, including catalogue designations, current and historical proper names, and foreign language names.
The Carte du Ciel and the Astrographic Catalogue were two distinct but connected components of a massive international astronomical project, initiated in the late 19th century, to catalogue and map the positions of millions of stars as faint as 11th or 12th magnitude. Twenty observatories from around the world participated in exposing and measuring more than 22,000 (glass) photographic plates in an enormous observing programme extending over several decades. Despite, or because of, its vast scale, the project was only ever partially successful – the Carte du Ciel component was never completed, and for almost half a century the Astrographic Catalogue part was largely ignored. However, the appearance of the Hipparcos Catalogue in 1997 has led to an important development in the use of this historical plate material.
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit.
Eta Ophiuchi is a binary star in the constellation of Ophiuchus. Based on parallax measurements taken during the Hipparcos mission, it is approximately 88 light-years from the Sun.
Mu Geminorum or μ Geminorum, formally named Tejat, is a single star in the northern constellation of Gemini. From parallax measurements obtained during the Hipparcos mission, it is roughly 230 light-years distant from the Sun. The position of the star near the ecliptic means that it is subject to lunar occultations.
Beta Cancri, also named Tarf, is the brightest star in the zodiacal constellation of Cancer. It has an apparent visual magnitude of +3.5 and an absolute magnitude of −1.2. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 290 light-years distant from the Sun. An exoplanet, designated Beta Cancri b, is believed to be orbiting the star.
Alpha Aquarii, officially named Sadalmelik, is a single star in the constellation of Aquarius. The apparent visual magnitude of 2.94 makes this the second-brightest star in Aquarius. Based upon parallax measurements made during the Hipparcos mission, it is located at a distance of roughly 520 light-years from the Sun. It is drifting further away from the Sun with a radial velocity of 7.5 km/s.
The Washington Double Star Catalog, or WDS, is a catalog of double stars, maintained at the United States Naval Observatory. The catalog contains positions, magnitudes, proper motions and spectral types and has entries for 141,743 pairs of double stars. The catalog also includes multiple stars. In general, a multiple star with n components will be represented by entries in the catalog for n-1 pairs of stars.
Epsilon Cancri is a white-hued binary star system in the zodiac constellation of Cancer. It is the brightest member of the Beehive Cluster with an apparent visual magnitude of +6.29, which is near the lower limit of visibility with the naked eye. The annual parallax shift of 5.4 mas as seen from Earth yields a distance estimate of approximately 606 light-years from the Sun.
Mu Sagittarii is a multiple star system in the constellation of Sagittarius. The brightest component, designated Mu Sagittarii Aa, is formally named Polis. The system is 3,000 light-years from the Sun and is part of the Sgr OB1 stellar association.
Zeta Aquilae, or ζ Aquilae, is a binary star system in the equatorial constellation of Aquila. It is readily visible with the naked eye, being of the third magnitude. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 83 light-years distant from the Sun. It is a candidate member of the TW Hydrae association of co-moving stars.
Gamma Boötis, Latinised from γ Boötis, is a binary star system in the northern constellation of Boötes the herdsman, forming the left shoulder of this asterism. The primary component has the proper name Seginus, the traditional name of the Gamma Bootis system. It has a white hue and is visible to the naked eye with a typical apparent visual magnitude of +3.03. Based on parallax measurements obtained during the Hipparcos mission, it is located at a distance of approximately 85 light-years from the Sun, but is drifting closer with a radial velocity of −32 km/s.
Kappa Persei or κ Persei, is a triple star system in the northern constellation of Perseus. Based upon an annual parallax shift of 28.93 mas, it is located at a distance of 113 light-years from the Sun.
Eta Eridani, officially named Azha, is a giant star in the constellation of Eridanus. Based on parallax measurements taken during the Hipparcos mission, it is approximately 137 light-years from the Sun.
The PPM Star Catalogue is the successor of the SAO Catalogue. It contains precise positions and proper motions of 378,910 stars 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.
The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education, Outreach and Heritage.
The Gaia catalogues are star catalogues created using the results obtained by Gaia space telescope.
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