The Nautical Almanac # 43 --- Atria (Alpha Trianguli Australis)

Atria (a contraction of its Latin name, Alpha Trianguli Australis) is the brightest star in the small southern constellation of Trianguli Australis The Southern (Engineer's) Triangle, known as one of the three constellations that make up "The Draughtsman's Tools" (the other two being Circinus The (Engineer's) Compass and Norma The (Engineer's) Square). It is the forty-third star in the Nautical Almanac. In Earth's skies it is so far south that it is sometimes referred to as the South Pole Star, though Miaplacidus could also get that designation. Neither is anywhere as close to the South Pole as Polaris is to the North Pole.

The Southern Triangle was formally added to the list of constellations in the 1700s, but it was recognized long before that. Amerigo Vespucci first named the constellation and its brightest star in a star catalogue published for the Medici family in 1503. 

From Earth, Atria is a moderately bright second magnitude star, and is considered the apex of the Triangle. It is a giant orange star of about 48 million years of age, and, based on its color, recently left its Main Sequence. This means it has begun to swell, and if placed at the center of our Solar System Atria's surface would reach the orbit of Venus. 

Atria is over 98 times the size of the Sun and is 5,309 times as luminous. It lies about 415 light years from Earth. Its temperature is 6,908 degrees Fahrenheit. 

Atria may be a binary with a Sun-sized star in orbit around it. It emits large amounts of X-Rays, a characteristic of young stars at the beginning of their Main Sequence, not older stars beginning to burn helium.