NOTABLE STARS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site Alnitak (Zeta Orionis) Alnitak is the left-hand star in Orion's Belt. Image: NASA 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. Visual magnitude 1.74 Absolute magnitude -5.26 Spectral type O9.5Ib Surface temperature 31,000 K Luminosity 100,000 Lsun Mass 20 Msun Distance 817 light-years 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 Related category    • NOTABLE STARS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP