In contemporary astronomy, 88 constellations are recognized by the International Astronomical Union. Each constellation is a region of the sky, bordered by arcs of right ascension and declination. Together they cover the entire celestial sphere, with their boundaries adopted officially by the International Astronomical Union in 1928 and published in 1930. The ancient Sumerians, and later the Greeks, established most of the northern constellations in international use today. The constellations along the ecliptic are called the zodiac. When explorers mapped the stars of the southern skies, European astronomers proposed new constellations for that region, as well as ones to fill gaps between the traditional constellations. In 1922, the International Astronomical Union adopted three-letter abbreviations for 89 constellations, the modern list of 88 plus Argo. After this, Eugène Joseph Delporte drew up boundaries for each of the 88 constellations so that every point in the sky belonged to one constellation.
History
Some constellations are no longer recognized by the IAU, but may appear in older star charts and other references. Most notable is Argo Navis, which was one of Ptolemy's original 48 constellations.
The 88 constellations depict 42 animals, 29 inanimate objects and 17 humans or mythological characters.
Abbreviations
Each IAU constellation has an official 3-letter abbreviation based on the genitive form of the constellation name. The majority of the abbreviations are just the first three letters of the constellation name, with the first character capitalised: Ori for Orion, Ara for Ara/Arae, Com for Coma Berenices. In some cases, the abbreviation is from the genitive form without appearing in the base name. In other cases, to unambiguously identify the constellation, such as 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. 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. Two cases are ambiguous: Leo for the constellation Leo could be mistaken for Leo Minor, and Tri for Triangulum could be mistaken for Triangulum Australe.
List
For help with the literary English pronunciations, see the. There is considerable diversity in how Latinate names are pronounced in English. For traditions closer to the original, see Latin spelling and pronunciation.
Asterisms
Various other unofficial patterns exist alongside the constellations. These are known as "asterisms". Examples include the Big Dipper/Plough and the Northern Cross. Some ancient asterisms, for example Coma Berenices, Serpens, and portions of Argo Navis, are now officially constellations.
