Alnilam

Alnilam
Location of Alnilam (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Pronunciation /ælˈnaɪlæm/[1]
Right ascension 05h 36m 12.8s[2]
Declination −01° 12′ 06.9″[2]
Apparent magnitude (V) 1.69[3] (1.64 – 1.74[4])
Characteristics
Evolutionary stage Blue supergiant
Spectral type B0 Ia[5]
U−B color index −1.03[3]
B−V color index −0.18[3]
Variable type α Cygni[4]
Astrometry
Radial velocity (Rv)25.9[6] km/s
Proper motion (μ) RA: 1.49[2] mas/yr
Dec.: −1.06[2] mas/yr
Parallax (π)1.65 ± 0.45 mas[2]
Distance1,180 ly
(361 pc)[7][a]
Absolute magnitude (MV)−6.89[8]
Details[9]
Mass40 M☉
Radius30.62 R☉
Luminosity419,600 L☉
Surface gravity (log g)3.02 cgs
Temperature26,540 K
Rotational velocity (v sin i)80 km/s
Age4.47 Myr
Other designations
Alnilam, ε Ori, 46 Orionis, Orionis, BD−01°969, FK5 210, HD 37128, HIP 26311, HR 1903, SAO 132346, TD1 4963, 參宿二
Database references
SIMBADdata

Alnilam is the central star of Orion's Belt in the equatorial constellation of Orion. It has the Bayer designation ε Orionis, which is Latinised to Epsilon Orionis and abbreviated Epsilon Ori or ε Ori. This is a massive, blue supergiant star some 1,200 light-years distant. It is estimated to be 419,600 times as luminous as the Sun, and 40 times as massive.

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