Constellations

There are 88 modern constellations, that are formally defined groupings of stars, in mapped regions of Earth's sky that covers the entire celestial sphere.
==IAU classifications==
In 1922, the International Astronomical Union (IAU) adopted the modern list of 88 constellations. After this, Eugène Joseph Delporte drew up precise boundaries for each constellation, so that every point in the sky belonged to exactly one constellation. In 1928, IAU had ratified and recognized 88 modern constellations, with contiguous boundaries defined by right ascension and declination. Therefore, any given point in a celestial coordinate system lies in one of the modern constellations. Some astronomical naming systems give the constellation where a given celestial object is found along with a designation in order to convey an approximate idea of its location in the sky. e.g. The Flamsteed designation for bright stars consists of a number and the genitive form of the constellation name.
==Abbreviations==
Each of the IAU constellations has an official 3 letter abbreviation. They are actually abbreviations of the genitive form of the constellation names, so some letters appearing in the abbreviation may come from the genitive form without appearing in the base name (as in Sge for Sagitta/Sagittae, to avoid confusion with Sagittarius, abbreviated Sgr). The majority of the abbreviations are just the first three letters of the constellation, with the first character capitalised: Ori for Orion, Ara for Ara/Arae, Com for Coma Berenices. In cases where this would not unambiguously identify the constellation, or where the name and its genitive differ in the first three letters, other letters beyond the initial three are used: Aps for Apus/Apodis, CrA for Corona Australis, CrB for Corona Borealis, Crv for Corvus. (Crater is abbreviated Crt to prevent confusion with CrA.) When letters are taken from the second word of a two-word name, the first letter from the second word is capitalised: CMa for Canis Major, CMi for Canis Minor. The abbreviations are unambiguous, with two exceptions. Leo for the constellation Leo could be mistaken for Leo Minor (abbreviated LMi), and Tri for Triangulum could be mistaken for Triangulum Australe (abbreviated TrA).
==References==
Category:Glossary