Alnitak (Zeta Orionis)
Alnitak is the left-hand star in Orion's Belt. Image: NASA.
Alnitak (Zeta Orionis) is the left hand star in Orion's Belt, the fifth brightest in the whole of Orion, and (in terms of apparent magnitude) the brightest O star in the sky. Its Arabic name comes from a phrase meaning "the belt of al Jauza." A B-type companion lies about 3 arc-seconds away, the pair orbiting each other with a period of several thousand years.
Like all O stars, Alnitak is a source of X-rays that seem to come from a stellar wind that blows from its surface at nearly 2,000 km/s. The X-rays are produced when blobs of gas in the wind crash violently into one another. Alnitak is probably only about 6 million years old and will eventually become a red supergiant before exploding as a supernova. In its vicinity are several dusty interstellar clouds, including, to the south, the Horsehead Nebula.
|surface temperature||31,000 K|
|position||R.A. 05h 40m 45.5s,
Dec. -01° 56' 34"
|other designations||Al Nitak, 50 Ori, HR 1948/9,
BD -02°1338, HD 37742,
SAO 132444, HIP 26727