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.
Subjects: Astronomy and Astrophysics.