Orion (astronomy)

Orion in astronomy, constellation located on the celestial equator. It is one of the most conspicuous and easily recognizable constellations in the entire sky. From ancient times it has been mentioned in the literature of many peoples and is traditionally depicted as the figure of a warrior. Four bright stars form a quadrangle marking his shoulders and feet; brilliant red Betelgeuse (Alpha Orionis) at his right shoulder, Bellatrix (Gamma Orionis) at his left shoulder, and dazzling Rigel (Beta Orionis) at his left foot are all among the 25 brightest stars in the sky, while Saiph (Kappa Orionis) at the right foot is of second magnitude. Three bright second-magnitude stars form a belt almost along the celestial equator; hanging from the belt is a sword of dimmer stars and including the famous Great Nebula (M42). Orion reaches its highest point in the evening sky in late January.

Orion Prominent constellation, representing a hunter. Four young stars form a conspicuous quadrilateral containing a row of three other stars representing his belt.

Orion (abbr. Ori, gen. Orionis) A magnificent constellation on the celestial equator, representing a great hunter of Greek mythology. Orion is outlined by the prominent stars Betelgeuse (Alpha Orionis), Rigel (Beta Orionis, the constellation's brightest star), Bellatrix (Gamma Orionis), and Saiph (Kappa Orionis). A line of three stars, Alnilam (Epsilon Orionis), Alnitak (Zeta Orionis), and Mintaka (Delta Orionis), make up the Belt of Orion. The famous Orion Nebula, M42, contains the multiple star known as the Trapezium. On the southern edge of the Orion Nebula is the double star Iota Orionis, magnitudes 2.8 and 6.9. North of the Orion Nebula is another bright nebula, NGC 1977, and further north again is the 5th-magnitude open cluster NGC 1981. This complex of nebulosity and clusters forms the Sword of Orion, hanging from Orion's belt. Sigma Orionis is an impressive multiple star of magnitudes 3.8, 6.6, 6.7, and 8.8. Eta Orionis is a close double, magnitudes 3.8 and 4.8. The dark Horsehead Nebula intrudes into a faint strip of nebulosity, IC 434, which runs south of Alnitak. The Orionid meteors radiate from the constellation every October.