Large Scale Structure of Orion

The Orion star formation region is the closest region of massive star formation. As such, it affords us a unique opportunity of studying the formation of high-mass stars. (Here, high-mass stars are those with masses greater than one solar mass). The Orion complex lies 160á pc below the galactic plane, and 450á pc from earth. The star forming region consists chiefly of Orioná A and B, molecular clouds named for their most prominent HII regions. Each of the two clouds contains about 10⁵ M of material (Genzel & Stutzki 1989). Orioná B (covering about 1200á pc²) is associated with the Horsehead Nebula and NGCá 2023, 2024, 2064, 2068, and 2071. Orion A, southwest of this, covers about 1800á pc² and is associated with the Orion Nebula (aka NGCá 1976, M42). The oldest of the stars in the Orion A and B clouds are younger than 12á Myr (Brown, deá Geus, & deá Zeeuw 1994).

á© Copyright Astronomical Society of Australia 1997