Peg · Pegasi
Pegasus Constellation
IAU constellation mapPegPegasus (Peg) is one of the 88 constellations recognised by the International Astronomical Union. It covers 1121 square degrees of the northern sky in quadrant NQ4. Its brightest star is Enif. The Latin genitive of the name is Pegasi, used to form star names within the constellation. In Greek mythology, Pegasus is associated with greek tradition. The IAU standardised all constellation boundaries in 1930.
Quick facts
- IAU name
- Pegasus
- Abbreviation
- Peg
- Latin genitive
- Pegasi
- Hemisphere
- northern
- Area
- 1,121 sq deg
- Brightest star
- Enif
- Quadrant
- NQ4
- Family
- Perseus
- Mythology origin
- Greek
- Discovery era
- Ptolemy's 48 (Almagest, c. 150 CE)
Mythology
Pegasus, the winged horse, sprang from the blood of the Gorgon Medusa when Perseus decapitated her. The hero Bellerophon later tamed Pegasus with the help of a golden bridle provided by Athena, and rode the winged horse to slay the fire-breathing Chimaera. Bellerophon then attempted to ride Pegasus to Olympus — an act of overreaching hubris (hybris) — but Zeus sent a gadfly to sting the horse, throwing Bellerophon back to Earth where he wandered crippled and blind for the rest of his days. Pegasus continued to Olympus alone and became the carrier of Zeus's thunderbolts. The Great Square of Pegasus — an asterism formed by three stars in Pegasus (Markab, Scheat, Algenib) and one borrowed from Andromeda (Alpheratz) — is one of the most useful navigational landmarks in the autumn sky. 51 Pegasi, a sun-like star in this constellation only 50.9 light-years from Earth, was the first sun-like star (in 1995) confirmed to host an extrasolar planet — a discovery by Michel Mayor and Didier Queloz that earned the 2019 Nobel Prize in Physics. Enif (Epsilon Pegasi), the constellation's brightest star at magnitude 2.38, is an orange supergiant.
Sources: Hesiod Theogony 281-286; Apollodorus Bibliotheca 2.3.2; Hyginus Astronomica 2.18.
Overview
Pegasus is one of the 88 constellations formally recognised by the International Astronomical Union (IAU). It occupies 1121 square degrees of sky in the northern hemisphere sky, best visible at latitudes between +90 and -60 degrees in September. The constellation belongs to the Perseus family of constellations. Its Latin genitive is Pegasi, the form used when naming stars within the constellation — for example, the brightest star Enif may appear in catalogues as Alpha Pegasi 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 Pegasus is Enif. Individual stars within Pegasus are conventionally named using Bayer designation — Greek letters followed by the Latin genitive of the constellation name (Pegasi) — introduced by Johann Bayer in his 1603 star atlas Uranometria. Flamsteed numbers (numeric designators followed by Pegasus) were added by John Flamsteed in his 1712 catalogue. Variable stars, double stars, and deep-sky objects within the Pegasus boundary are catalogued by the IAU with the abbreviation Peg.
History and mythology
The figure of Pegasus 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.
Sources & further reading (2)
- official-iau — accessed 2026-05-06
- encyclopedia — accessed 2026-05-06
Frequently asked questions
What does the name Pegasus mean?
Pegasus is the Latin name used by the IAU to designate this constellation. The name comes from classical Latin and Greek astronomical tradition. In star catalogues, stars within Pegasus are designated using the genitive form of the name (e.g. Alpha Pegasus or similar Latin genitive forms) — a naming convention introduced by Johann Bayer in his 1603 atlas Uranometria and still in use today.
How large is Pegasus compared to other constellations?
Pegasus covers 1121 square degrees of sky. The full sphere of the sky contains 41,253 square degrees, so Pegasus occupies about 2.7% of the total sky. For comparison, the largest constellation is Hydra at 1303 square degrees; the smallest is Crux at 68 square degrees.
When and where is Pegasus visible?
Pegasus is primarily a northern hemisphere constellation, best seen from mid-northern latitudes. Southern hemisphere observers may see it low on the horizon depending on their latitude. The brightest star, Enif, serves as the main visual anchor for locating the constellation. As with all constellations, the best viewing conditions are a dark sky away from artificial light pollution, with the constellation high enough above the horizon to minimise atmospheric absorption.
