Ari · Arietis
Aries Constellation
IAU constellation mapAriAries (Ari) is one of the 88 constellations recognised by the International Astronomical Union. It covers 441 square degrees of the northern sky in quadrant NQ1. Its brightest star is Hamal. The Latin genitive of the name is Arietis, used to form star names within the constellation. In Greek mythology, Aries is associated with greek tradition. The IAU standardised all constellation boundaries in 1930.
Quick facts
- IAU name
- Aries
- Abbreviation
- Ari
- Latin genitive
- Arietis
- Hemisphere
- northern
- Area
- 441 sq deg
- Brightest star
- Hamal
- Quadrant
- NQ1
- Family
- Zodiac
- Mythology origin
- Greek/Babylonian
- Discovery era
- Ptolemy's 48 (Almagest, c. 150 CE)
Mythology
Aries represents the ram Chrysomallus, whose golden fleece became the object of the famous expedition of Jason and the Argonauts. In Greek myth, Chrysomallus bore Phrixus and Helle on his back as they fled their murderous stepmother Ino across the sea. When Helle fell into the strait that henceforth bore her name (the Hellespont, modern Dardanelles), Phrixus continued east to Colchis, where he sacrificed the ram to Zeus and hung its golden fleece in a sacred grove guarded by a sleepless serpent. The god Hermes, or according to some sources the god himself, then placed the ram among the stars in recognition of his service. Centuries later Jason, prince of Iolcos, led the Argonauts to Colchis to retrieve the fleece, assisted by the sorceress Medea. In Babylonian astronomy the figure is attested from around 2000 BCE as the 'Agricultural Laborer', and the first point of Aries was the vernal equinox at that epoch — a point now shifted by precession into Pisces. The name passed through Persian and Arabic astronomical tradition before being fixed in the Renaissance star catalogues.
Sources: Apollodorus Bibliotheca 1.9.1; Aratus Phaenomena 225-232; Hyginus Astronomica 2.20.
Overview
Aries is one of the 88 constellations formally recognised by the International Astronomical Union (IAU). It occupies 441 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 Arietis, the form used when naming stars within the constellation — for example, the brightest star Hamal may appear in catalogues as Alpha Arietis 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 Aries is Hamal. Individual stars within Aries are conventionally named using Bayer designation — Greek letters followed by the Latin genitive of the constellation name (Arietis) — introduced by Johann Bayer in his 1603 star atlas Uranometria. Flamsteed numbers (numeric designators followed by Aries) were added by John Flamsteed in his 1712 catalogue. Variable stars, double stars, and deep-sky objects within the Aries boundary are catalogued by the IAU with the abbreviation Ari.
History and mythology
The figure of Aries 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 Aries mean?
Aries 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 Aries are designated using the genitive form of the name (e.g. Alpha Aries 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 Aries compared to other constellations?
Aries covers 441 square degrees of sky. The full sphere of the sky contains 41,253 square degrees, so Aries occupies about 1.1% 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 Aries visible?
Aries 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, Hamal, 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.
