Cen · Centauri
Centaurus Constellation
IAU constellation mapCenCentaurus (Cen) is one of the 88 constellations recognised by the International Astronomical Union. It covers 1060 square degrees of the southern sky in quadrant SQ3. Its brightest star is Rigil Kentaurus. The Latin genitive of the name is Centauri, used to form star names within the constellation. In Greek mythology, Centaurus is associated with greek tradition. The IAU standardised all constellation boundaries in 1930.
Quick facts
- IAU name
- Centaurus
- Abbreviation
- Cen
- Latin genitive
- Centauri
- Hemisphere
- southern
- Area
- 1,060 sq deg
- Brightest star
- Rigil Kentaurus
- Quadrant
- SQ3
- Family
- Hercules
- Mythology origin
- Greek
- Discovery era
- Ptolemy's 48 (Almagest, c. 150 CE)
Mythology
Centaurus represents a centaur — the hybrid creatures of Greek myth with the head and torso of a man and the body and legs of a horse. The centaur in this constellation is usually identified as Chiron, the wise and learned centaur who served as tutor to heroes including Achilles, Jason, and Asclepius the healer. Chiron was accidentally wounded by a poisoned arrow shot by Heracles and, being immortal, could not die — so to escape the unending agony, he surrendered his immortality to free Prometheus and was placed honourably in the stars. The constellation contains the nearest star system to the Solar System: the triple system Alpha Centauri, located only 4.37 light-years away. Of the three stars, Rigil Kentaurus (Alpha Centauri A and B, a binary pair) and Proxima Centauri (Alpha Centauri C) are the components; Proxima Centauri at 4.24 light-years is the single nearest star. Rigil Kentaurus has a combined apparent magnitude of -0.27, making it the third brightest star in the night sky. Centaurus A (NGC 5128) is a nearby radio galaxy and the fifth-brightest galaxy in the sky, visible to the naked eye from southern latitudes.
Sources: Aratus Phaenomena 432-440; Hyginus Astronomica 2.38; Apollodorus Bibliotheca 2.5.4.
Overview
Centaurus is one of the 88 constellations formally recognised by the International Astronomical Union (IAU). It occupies 1060 square degrees of sky in the southern hemisphere sky, best visible at latitudes between +45 and -90 degrees in June. The constellation belongs to the Hercules family of constellations. Its Latin genitive is Centauri, the form used when naming stars within the constellation — for example, the brightest star Rigil Kentaurus may appear in catalogues as Alpha Centauri 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 Centaurus is Rigil Kentaurus. Individual stars within Centaurus are conventionally named using Bayer designation — Greek letters followed by the Latin genitive of the constellation name (Centauri) — introduced by Johann Bayer in his 1603 star atlas Uranometria. Flamsteed numbers (numeric designators followed by Centaurus) were added by John Flamsteed in his 1712 catalogue. Variable stars, double stars, and deep-sky objects within the Centaurus boundary are catalogued by the IAU with the abbreviation Cen.
History and mythology
The figure of Centaurus 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 Centaurus mean?
Centaurus 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 Centaurus are designated using the genitive form of the name (e.g. Alpha Centaurus 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 Centaurus compared to other constellations?
Centaurus covers 1060 square degrees of sky. The full sphere of the sky contains 41,253 square degrees, so Centaurus occupies about 2.6% 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 Centaurus visible?
Centaurus is primarily a southern hemisphere constellation. Observers at high northern latitudes cannot see it; it is best appreciated from the southern tropics or high southern latitudes. The brightest star, Rigil Kentaurus, 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.
