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Epsilon Orionis, 46 Orionis

Proper NameAlnilam
Bayer DesignationEpsilon Orionis
Flamsteed Number46 Orionis
HR (BSC)1903
Right Ascension5h 36m 13s
Declination-1° 12' 7"
Distancec.2,000 light years
c.600 parsecs
MagnitudeApparent: +1.7 to +0.6
Absolute: -6.4
Spectral ClassB0 Blue Supergiant
Optimum VisibilityDecember / January
NotesAn immense blue star of the supergiant classification, Alnilam or Epsilon Orionis is nearly forty times the diameter of the Sun, and across the entire spectrum emits nearly 600,000 times as much energy.

Alnilam is the central star of the three that make up Orion's Belt. It is the brightest of the three stars, with a marginally brighter apparent magnitude than Alnitak to the east (left) in this image. Imagery provided by Aladin sky atlas

Location of Alnilam

Alnilam lies at the centre of the richly starred region of Orion, forming the 'buckle' on Orion's prominent Belt.

The buckle on Orion's Belt - the central of the three famous stars that cross the central parts of Orion. Alnilam is a blue supergiant, a massive and hot star. It lies close to the dense Orion Molecular Cloud, and brightens part of this cloud to form its own reflection nebula, catalogued as NGC 1990 and commonly known as the Epilson Orionis Nebula.


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