O R I O N

The bright stars and hydrogen clouds of Orion are one of the best studied regions of the Gould Belt. This infrared image represents Orion's Sword, shown horizontally rather than in its more familiar vertical setting. The blazing area near the center is the Trapezium Cluster, which is also the heart of the Orion Nebula, located at a distance of 415 parsecs (1350 light years; Menten 2007). Additional views of this region are available at Orion Nebula, Trapezium Cluster, and the APOD Archives.

The three stars of Orion's Belt are known (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 (780 to 910 light years) and Alnilam well separated at 410 parsecs (1335 light years; 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 (a shape that many also recognize as a tree), and not far below is the Horsehead Nebula.