Fomalhaut - Definition and Overview

Fomalhaut ("mouth of the fish" from the Arabic Fam al-Hut) is the seventeenth brightest star in the sky as seen from Earth. It is a first-magnitude, class A star on the main sequence approximately 25 light-years (7.688 parsecs) from Earth. It is part of the faint constellation Piscis Austrinus and as such is also known as Alpha Piscis Austrini (Alpha PsA).

Fomalhaut is believed to be a young star, only 200 million years old. The surface temperature of the star is around 8500 kelvins. Compared to the Sun, its mass is about 2.3, its luminosity is about 15, and its diameter is roughly 1.7. It is surrounded by an enormous disk of dust in a toroidal shape (5 AU to 90 AU), is believed to be protoplanetary, and emits considerable infrared radiation. A planet, designated Fomalhaut b, has been inferred from analysis of the dust cloud in 1998.

Over history there have been a large number of variations on the star's name. It was first identified in pre-history and there is archaeological evidence that it was part of rituals in 2500s BCE in Persia where it would have been one of the Persians' four "royal stars". In the religion of Stregheria, Fomalhaut is a fallen angel and quarter guardian of the northern gate.

• Right Ascension 22h 57m 39.05s
• Declination -29°37′20″
• Spectral Type A3V
• Apparent Magnitude 1.16
• B-V Colour 0.09