Alnilam


'''Alnilam''', also known as ε Orionis or 46 Orionis, is a large blue star in the constellation of Orion. It is the 30th brightest star in the sky, the 4th brightest in Orion, and a blue-white supergiant. It is the middle star of Orion's belt. Alnilam lights up [[NGC 1990. Photograph by Glen Youman.]] 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 10 PM on December 10. Alnilam's relatively simple spectrum has made it useful for studying the interstellar medium.

Other names and history

The name Alnilam derives from the Arabic Al Nitham or Al Nathm, which translates as "the String of Pearls". Related names also used to describe the star are Alnihan and Alnitam. Various other names have been used to refer to Orion's belt, the line of three stars formed by Alnitak, Alnilam, and Mintaka. They include: These stars also influenced the construction of the Pyramids of Giza.

Physical characteristics

Observation data
Right ascension (RA, α) (J2000,00) 05 h 36 m 12.8 s
Declination (Dec, δ) (J2000,00) -01° 12' 6.91"
Distance from Earth 1340Ly ± 500 LY (410 pc)
Visual brightness (V)  +1.70m
Absolute magnitude -6.39m
Physical characteristics
Mean Diameter (dS = 1,392,000 km)
Surface area  
Volume  
Mass
Relative mass to the Sun
(mS = 1.9891 × 1030 kg)		 ~ 20 mS
Density  
Surface gravity  
Spectral type B0 Ia (Blue Supergiant)
Surface temperature 11000 K to 25000 K
Age ~ 4 million years
Color (B-V) -0.19 (Blue-white)
V-I
Luminosity (LS = 3.827 × 1026 J s-1) ~ 23 000 LS
Orbital characteristics
Period of rotation 
Period
Alnilam will eventually turn into red supergiant. Astronomers say that it then explode as a supernova, and this is expected to take place within the next million years. 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. de:Alnilam ja:アルニラム Category:Orion constellation Category:Type-B stars Orionis, Epsilon Orionis, 46

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