Alnilam, a blue supergiant star in Orion
Alnilam is a blue supergiant star in the constellation Orion. At 1,341 light years away, it is the 30th brightest star in the Earth's sky, where it shines at an apparent visual magnitude of 1.69.
Alnilam (HIP 26311)
Alnilam is a blue supergiant star in the constellation Orion. At 1,341 light years away, it is the 30th brightest star in the Earth's sky, where it shines at an apparent visual magnitude of 1.69. Alnilam is the primary component of a multiple-star system. It is moving through the Galaxy at a speed of 27.5 km/s relative to the Sun and is part of the Orion Molecular Cloud and ASCC 19 and Collinder 70 and Sigma Orionis moving groups. Its projected Galactic orbit carries it between 25,200 and 28,500 light years from the center of the Galaxy.
Sky position: RA 5h 36.2m, Dec -1° 12'
Common designations: Alnilam, Epsilon Orionis, 46 Orionis, HIP 26311, HD 37128
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Brightest stars in Orion:
(list all)
| Rank | Mag. | Star |
| 1 | 0.18 | Rigel |
| 2 | 0.45 | Betelgeuse |
| 3 | 1.64 | Bellatrix |
4
| 1.69
) Alnilam
| Rank | Mag. | Star |
| 5 | 1.74 | Alnitak |
| 6 | 2.07 | Saiph |
| 7 | 2.25 | Mintaka |
| 8 | 2.75 | Hatsya |
| 9 | 3.19 | Tabit |
| 10 | 3.35 | Eta Orionis |
| 11 | 3.39 | Heka |
| 12 | 3.59 | Tau Orionis |
| 13 | 3.68 | Pi-4 Orionis |
| 14 | 3.71 | Pi-5 Orionis |
| 15 | 3.77 | Sigma Orionis |
| 16 | 4.06 | Omicron-2 Orionis |
| 17 | 4.09 | Phi-2 Orionis |
Hover over other bright stars to identify or click to jump.
Galactic Orbit of Alnilam
(compared to the Sun)
E
ccentricity: 6.2% vs. 16.0%Angle φ : -21.7°vs. 26.0°
Semi-major axis : 8,234 pc vs. 8,686 pc
Semi-minor axis: 8,218 pc vs. 8,574 pc
Focus-to-center
: 508 pcvs. 1,388 pcSemilatus rectum : 8,203 pc vs. 8,464 pc
Perigalacticon: 7,726 pc vs. 7,297 pc
Apogalacticon
: 8,742 pcvs. 10,074 pcSome Tabulated XHIP Data for Alnilam
(see also: SIMBAD)
Astrometry
2007A&A...474..653V
| Position | Proper Motion | |
| Right Ascension: | 84.05338544° ±0.33 mas | 1.44 ±0.42 mas/yr. |
| Declination: | -1.20191724° ±0.19 mas | -0.78 ±0.19 mas/yr. |
| Galactic Longitude: | 205.21206247° | 1.37 mas/yr. |
| Galactic Latitude: | -17.24173331° | 0.90 mas/yr. |
Parallax: 1.65 ± 0.45 mas
Spectrography
Spectral Type: B0Ib 2009A&A...501..297Z.
Radial Velocity: 27.30 ±0.80 km/s [A rating] 2006AstL...32..759G.
Iron Abundance [Fe/H]:
n/a
Photometry
band
magnitude
Abs. Mag.
U
0.48
-7.59
B
1.51
-6.56
V
1.69
-6.38
R
I
1.85
-6.22
J
2.19
-5.88
H
2.41
-5.66
K
2.27
-5.80
B-V: -0.18 V-I: -0.16
Derivations
Heliocentric distance: 411.22 pc (fitted to cluster)
Galactocentric distance: 7,758 pc
Transverse velocity: 3.2 km/s
3D heliocentric position and motion:
|
toward: |
Galactic center | Galactic rotation | North Galactic Pole |
| Position ( X, Y, Z) | -355.3 pc | -167.3 pc | -121.9 pc |
| Velocity (U, V, W) | -22.9 km/s | -13.7 km/s | -6.4 km/s |