Piscis Austrini is the Latin genitive form of the constellation name Piscis Austrinus (the Southern Fish). In astronomical nomenclature, the genitive case is used in Bayer and Flamsteed star designations to indicate which constellation a star belongs to. For example, the brightest star in the constellation is formally designated Alpha Piscis Austrini, commonly known as Fomalhaut.
Piscis Austrinus is a constellation in the southern celestial hemisphere. Its name is Latin for "the southern fish," distinguishing it from the larger constellation Pisces, which represents a pair of fish. It was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations recognized by the International Astronomical Union.
Key features of the constellation:
- Abbreviation: PsA
- Genitive: Piscis Austrini (pronounced /ˈpaɪsɪs ɒˈstraɪnaɪ/)
- Brightest star: Fomalhaut (Alpha Piscis Austrini), magnitude 1.16, the 18th-brightest star in the night sky, located approximately 25 light-years from Earth.
- Second-brightest star: Epsilon Piscis Austrini, magnitude 4.17, a blue-white main-sequence star about 400 light-years distant.
- Notable objects: Lacaille 9352 (one of the brightest red dwarf stars in the night sky), the blazar PKS 2155-304, and several exoplanet-hosting stars such as HD 205739, HD 216770, and HD 207832.
- Bordering constellations: Capricornus, Microscopium, Grus, Sculptor, and Aquarius.
- Best visibility: At 9:00 p.m. during the month of October, visible at latitudes between +55° and −90°.
Mythology: In Greek mythology, Piscis Austrinus is known as the Great Fish, portrayed as swallowing the water being poured out by Aquarius. The two fish of the constellation Pisces are said to be the offspring of this Great Fish. In Egyptian mythology, the fish saved the life of the goddess Isis, who placed it and its descendants into the heavens as constellations.
