mardi 23 septembre 2008

Orion 7

Bellatrix (γ Orionis) est une étoile géante bleue de la constellation d'Orion, 3e par sa magnitude (+1,6) et de type spectral B2.
Le nom de Bellatrix provient du latin et signifie "la guerrière".

Alnilam is a large blue star in the constellation of Orion. It also has the modern name Epsilon Orionis (ε Ori / ε Orionis). Its Flamsteed designation is 46 Orionis.
It is the 30th brightest star in the sky (the 4th brightest in Orion) and as a blue-white supergiant it is one of the most luminous stars known. Together with Mintaka (Delta Orionis) and Alnitak (Zeta Orionis), the three stars make up the belt of Orion, known by many names across many ancient cultures. Alnilam is the middle star.
It is also one of the 57 stars used in celestial navigation. For middle latitudes, it is at its highest point in the sky around midnight on December 15.
Alnilam's relatively simple spectrum has made it useful for studying the interstellar medium. Within the next million years, this star may turn into a red supergiant and explode as a supernova. It is surrounded by a molecular cloud, NGC 1990, which it brightens to make a reflection nebula. Its stellar winds may reach up to 2000 km/s, causing it to lose mass about 20 million times more rapidly than the Sun.

The name Alnilam derives from the Arabic النظام an-niżām, related to the word نظم nażm "string of pearls". Related spellings are Alnihan and Alnitam: all three variants are evidently mistakes in transliteration or copy errors.

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