Corona Australis

Corona Australis is a constellation found in the Southern Celestial Hemisphere. Its Latin name translates to "southern crown," making it the southern equivalent of Corona Borealis, the northern crown. The 2nd-century astronomer Ptolemy listed it among his 48 constellations, and it is still counted among the 88 modern ones. The Ancient Greeks saw it as a wreath rather than a crown, linking it to Sagittarius or Centaurus. Other cultures have compared its pattern to a turtle, an ostrich nest, a tent, or a rock hyrax's hut.

Though dimmer than its northern counterpart, the constellation stands out due to the oval or horseshoe shape formed by its brighter stars. Its two brightest stars, Alpha and Beta Coronae Australis, both shine at an apparent magnitude of about 4.1. Epsilon Coronae Australis is the brightest example of a W Ursae Majoris variable star in the southern sky. Situated along the Milky Way, Corona Australis hosts one of the closest star-forming regions to our Solar System: the Corona Australis Molecular Cloud, a dusty dark nebula roughly 430 light-years away. This cloud contains stars in their earliest stages of life. The variable stars R and TY Coronae Australis illuminate parts of the nebula, causing its brightness to change.

The International Astronomical Union (IAU) officially entered the constellation's name as "Corona Australis" in 1922 when it established the 88 modern constellations. In 1932, the IAU's commission on notation recorded the name as "Corona Austrina" when approving a list of four-letter abbreviations for constellations. Those abbreviations were repealed in 1955, and the IAU now uses "Corona Australis" exclusively.

Corona Australis is a small constellation, bordered by Sagittarius to the north, Scorpius to the west, Telescopium to the south, and Ara to the southwest. Its three-letter abbreviation, adopted by the IAU in 1922, is "CrA." Belgian astronomer Eugène Delporte set the official constellation boundaries in 1930, defining them with a polygon of four segments. In the equatorial coordinate system, these borders span right ascension from 17h 58.3m to 19h 19.0m and declination from −36.77° to −45.52°. Covering 128 square degrees, it ranks 80th in area among the constellations. It culminates at midnight around June 30.