O R I O N

The bright stars and extensive nebulae of the constellation Orion are one of the most dramatic regions of the Gould Belt, both visually and dynamically. This infrared image represents the Great Nebula in Orion, which contains many of the most active nearby stellar nurseries. It is located at a distance of 415 parsecs (1350 light years; Menten 2007) in the direction of Orion's Sword. Additional views of this large region are available at Orion Nebula, Trapezium Cluster, Evolution Images, and the APOD Archives.

The three stars of Orion's Belt, known from left to right as Alnitak, Alnilam, and Mintaka, or alternatively as Zeta, Epsilon, and Delta Orionis. All are very young, with ages between 4 and 6 million years. These stars are likely members of the Gould Belt, with Alnitak and Mintaka located at a distance of 240 to 280 parsecs and Alnilam a bit farther at 410 parsecs (see individual pages at Stars by Jim Kaler). Alnitak is a binary consisting of an O star and a B star; Alnilam is probably a single B0 star; and Mintaka is a quadruple system, with a central binary consisting of an O star and a B star plus a more distant binary of uncertain spectral type in orbit around them. Largely surrounding Alnitak is an extension of the Orion region's vast molecular cloud complex; to the left of the star is the dark shadow of the Flame Nebula, and not far below is the well-known Horsehead Nebula.