Alpha Trianguli Australis

Alpha Trianguli Australis (Latinised from α Trianguli Australis, abbreviated Alpha TrA, α TrA), officially named Atria (), is the brightest star in the southern constellation of Triangulum Australe, forming an apex of a triangle with Beta Trianguli Australis and Gamma Trianguli Australis that gives the constellation its name (Latin for southern triangle).

Nomenclature

α Trianguli Australis (Latinised to Alpha Trianguli Australis) is the star's Bayer designation. The historical name Atria is a contraction. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Atria for this star.

In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 三角形 (Sān Jiǎo Xíng), meaning Triangle, refers to an asterism consisting of α Trianguli Australis, β Trianguli Australis and γ Trianguli Australis. Consequently, α Trianguli Australis itself is known as 三角形三 (Sān Jiǎo Xíng sān, English: the Third Star of Triangle.)

Physical characteristics

Atria is a red supergiant star with an apparent magnitude of +1.91. Based upon parallax measurements, this star is located roughly 391 light-years (120 parsecs) distant from the Earth. The estimated age of the star is 48 million years old; sufficiently old for a massive star to evolve away from the main sequence. N. Covacs give Atria a stellar classification of K2IIb-IIIa, with the luminosity class indicating an evolutionary stage between a bright giant and a regular giant.