Pisces Constellation

Mythology

Pisces, the Fish, represents two fish swimming in opposite directions with their tails bound together by a cord — a figure attested in Babylonian astronomy from the 13th century BCE as a pair of fish-tailed deities. In Greek mythology the two fish represent Aphrodite and her son Eros, who leapt into the Euphrates river and transformed themselves into fish to escape the monster Typhon during the gods' flight into Egypt; to avoid losing each other in the water they tied their tails together with a cord. Alternatively, the fish represent the fish that found the egg from which Aphrodite was born (though this is a more confused tradition). The vernal equinox, the point where the Sun crosses the celestial equator moving northward, is currently located in Pisces — this point is called 'the first point of Aries' but has precessed from Aries through Taurus and into Pisces over the past two millennia. Eta Piscium (Kullat Nunu in Arabic, meaning 'cord of the fish') is the constellation's brightest star at magnitude 3.62. The galaxy NGC 520 in Pisces is a striking example of two galaxies in the early stages of collision and merger.

Sources: Aratus Phaenomena 240-246; Hyginus Astronomica 2.30; Ovid Fasti 2.457-474.

Overview

Pisces is one of the 88 constellations formally recognised by the International Astronomical Union (IAU). It occupies 889 square degrees of sky in the northern hemisphere sky, best visible at latitudes between +90 and -60 degrees in December. The constellation belongs to the Zodiac family of constellations. Its Latin genitive is Piscium, the form used when naming stars within the constellation — for example, the brightest star Eta Piscium may appear in catalogues as Alpha Piscium or similar. The IAU standardised the boundaries of all 88 constellations in 1930 under the direction of Eugène Delporte, using straight lines of right ascension and declination to eliminate the ambiguities of earlier variable-boundary systems.

Notable stars

The brightest star in Pisces is Eta Piscium. Individual stars within Pisces are conventionally named using Bayer designation — Greek letters followed by the Latin genitive of the constellation name (Piscium) — introduced by Johann Bayer in his 1603 star atlas Uranometria. Flamsteed numbers (numeric designators followed by Pisces) were added by John Flamsteed in his 1712 catalogue. Variable stars, double stars, and deep-sky objects within the Pisces boundary are catalogued by the IAU with the abbreviation Psc.

History and mythology

The figure of Pisces appears in the classical astronomical tradition. Ptolemy included this constellation in the Almagest (c. 150 CE), the definitive ancient catalogue of 48 constellations, which formed the foundation for Islamic, medieval European, and Renaissance astronomy. The constellation's figure and mythology were transmitted through works such as Aratus's Phaenomena, Eratosthenes's Catasterismi, and Hyginus's Astronomica. See the Mythology section above for the full narrative.