In astronomy, a variable-star designation is a unique identifier given to variable stars. It uses a variation on the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in which the star lies. See List of constellations for a list of constellations and the genitive forms of their names. The identifying label can be one or two Latin letters or a V plus a number (e.g. V399). Examples are R Coronae Borealis, YZ Ceti, V603 Aquilae.
The current naming system is: [1]
The second letter is never nearer the beginning of the alphabet than the first, e.g., no star can be BA, CA, CB, DA and so on.
In the early 19th century few variable stars were known, so it seemed reasonable to use the letters of the Latin script. Because very few constellations contained stars with uppercase Latin-letter Bayer designation greater than Q, the letter R was chosen as a starting point so as to avoid confusion with letter spectral types or the (now rarely used) Latin-letter Bayer designations. Although Lacaille had used uppercase R to Z letters in a few cases, for example X Puppis (HR 2548), these designations were either dropped or accepted as variable star designations. [3] The star T Puppis was accepted by Argelander as a variable star and is included in the General Catalogue of Variable Stars with that designation but is now classed as non-variable. [4]
This variable star naming convention was developed by Friedrich W. Argelander. There is a widespread belief according to which Argelander chose the letter R for German rot or French rouge, both meaning "red", because many variable stars known at that time appear red. [5] However, Argelander's own statement disproves this. [6]
By 1836, even the letter S had only been used in one constellation, Serpens. With the advent of photography the number of variables piled up quickly, and variable star names soon fell into the Bayer trap of reaching the end of the alphabet while still having stars to name.[ citation needed ] After two subsequent supplementary double-lettering systems hit similar limits, numbers were finally introduced. [6]
As with all categories of astronomical objects, names are assigned by the International Astronomical Union (IAU). The IAU delegates the task to the Sternberg Astronomical Institute and the Institute of Astronomy of the Russian Academy of Sciences in Moscow, Russia. Sternberg publishes the General Catalog of Variable Stars (GCVS), which is periodically (approximately once every two years) amended by the publication of a new "Name-List" of variable stars. [7] For example, in December 2011 the 80th Name-List of Variable Stars, Part II, was released, containing designations for 2,161 recently discovered variable stars; these brought the total number of variable stars in the GCVS to 45,678. Among the newly designated objects were V0654 Aurigae, V1367 Centauri, and BU Coronae Borealis. [8]
A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. The brighter stars were assigned their first systematic names by the German astronomer Johann Bayer in 1603, in his star atlas Uranometria. Bayer catalogued only a few stars too far south to be seen from Germany, but later astronomers supplemented Bayer's catalog with entries for southern constellations.
Alpha Coronae Borealis, officially named Alphecca, is an eclipsing binary star in the constellation of Corona Borealis. It is located about 75 light years from the Sun and contains two main sequence stars, one class A and one class G.
Omicron Velorum is a star in the constellation Vela. It is the brightest member of the loose naked eye open cluster IC 2391, also known as the ο Velorum Cluster.
47 Boötis is a binary star system in the northern constellation of Boötes, located 261 light years away from the Sun. It has the Bayer designation k Boötis; 47 Boötis is the Flamsteed designation. The system is visible to the naked eye as a faint, white-hued star with a combined apparent visual magnitude of 5.58. It is moving closer to the Earth with a heliocentric radial velocity of −13 km/s.
Omicron1 Canis Majoris is a red supergiant star in the constellation Canis Major. It is also a variable star.
UW Canis Majoris is a star in the constellation Canis Major. It is classified as a Beta Lyrae eclipsing contact binary and given the variable star designation UW Canis Majoris. Its brightness varies from magnitude +4.84 to +5.33 with a period of 4.39 days. Bode had initially labelled it as Tau2 Canis Majoris, but this designation had been dropped by Gould and subsequent authors.
L2 Puppis (also known as HD 56096) is a giant star in the constellation of Puppis and is located between the bright stars Canopus and Sirius. It is a semi-regular pulsating star.
A slow irregular variable is a variable star that exhibit no or very poorly defined periodicity in their slowly changing light emissions. These stars have often been little-studied, and once more is learnt about them, they are reclassified into other categories such as semiregular variables.
Omicron Puppis (ο Puppis) is candidate binary star system in the southern constellation of Puppis. It is visible to the naked eye, having a combined apparent visual magnitude of +4.48. Based upon an annual parallax shift of 2.30 mas as seen from Earth, it is located roughly 1,400 light years from the Sun.
NS Puppis is an irregular variable star in the constellation Puppis. Its apparent magnitude varies between 4.4 and 4.5.
NV Puppis, also known as υ1 Puppis, is a class B2V star in the constellation Puppis. Its apparent magnitude is 4.67 and it is approximately 800 light years away based on parallax.
MX Puppis is a class B1.5IV star in the constellation Puppis. Its apparent magnitude varies irregularly between magnitude 4.6 and 4.9 and it is classified as a Gamma Cassiopeiae variable. It is approximately 930 light years away based on parallax.
OU Puppis is a chemically peculiar class A0 star in the constellation Puppis. Its apparent magnitude is about 4.9 and it is approximately 188 light-years away based on parallax.
HD 51799 is a class M1III star in the constellation Puppis. Its apparent magnitude is 4.95 and it is approximately 860 light years away based on parallax.
Z Ursae Minoris is a carbon star and R Coronae Borealis variable in the constellation Ursa Minor.
W Coronae Borealis is a Mira-type long period variable star in the constellation Corona Borealis. Its apparent magnitude varies between 7.8 and 14.3 over a period of 238 days.
NW Puppis, also known as υ2 Puppis, is a star in the constellation Puppis. Located around 910 light-years distant, it shines with a luminosity approximately 1,108 times that of the Sun and has a surface temperature of 15,000 K. Anamarija Stankov ruled this star out as a Beta Cephei variable.
CX CMa is a blue variable star in the Canis Major constellation. Discovery of this variable is usually credited to German Astronomer Cuno Hoffmeister in 1931, although this remains uncertain.
MZ Puppis is a red supergiant star in the constellation of Puppis. It has a radius of 400 R☉.
HD 62058, is a variable star in the constellation Puppis. It is a rare yellow hypergiant and a candidate member of the open cluster NGC 2439. It is also an MK spectral standard for the class G2 0-Ia.
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