Fomalhaut (Alpha Piscis Austrini, Alpha PsA, a Piscis Austrini, a PsA) is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. It is a class A star on the main sequence approximately from Earth as measured by the Hipparcos astrometry satellite. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is classified as a Vega-like star that emits excess infrared radiation, indicating it is surrounded by a circumstellar disk. Fomalhaut, K-type star TW Piscis Austrini and M-type star LP 876-10 constitute a triple system even though the companions are separated by several degrees.