Alnitak
Alnitak is the eastern most of the three stars in Orions’ belt. It is also known as Zeta Orionis. Alnitak is a triple star that with the primary being a blue supergiant. The other two stars are Delta Orionis and Epsilon Orionis.
Alnitak has been known since antiquity. Being a component of Orion’s belt, it has had widespread cultural significance. In 1819, the star was reported to be a double star by amateur German astronomer George Kunowsky. More recently, in 1998, the bright primary was found to have a close companion by a team from the Lowell Observatory. Initially thought to be around 1500 light years distant, the Alnitak system was found to be almost twice as close following measurement of its stellar parallax by the Hipparcos satellite published in 1996. Alnitak has a magnitude of +2.04.
Altnitak is a class O star. Type-O supergiants show strong stellar winds that produce optical spectral emission lines and thermal radio and X-ray emissions. How these stars produce high-energy X-rays, however, is still subject to intense research because they lack significant magnetic fields and are not sufficiently hot despite their very high surface temperatures. Although O-type stars have inner convection zones in their core, they are believed to lack outer convection zones, which astronomers considered necessary to create the hot and energetic plasmas confined in magnetic loops.
Alnitak’s surface burns at 31,000 kelvin. Massive stars use their fuel quickly and do not live very long. Alnitak is probably only about 6 million years old (as opposed to the Sun’s 4.5 billion year age) and it has already begun to die, hydrogen fusion having ceased in its core. The star will eventually become a red supergiant somewhat like Betelgeuse and almost certainly will explode as a supernova, leaving its companion orbiting a hot, madly spinning neutron star.
There is some more information about Alnitak here. Here on Universe Today we have a great article about the Orion constellation. Astronomy Cast offers a good episode about the telescopes that you will need to become serious enough to search the skies on your own.
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