Sigma Orionis, a blue main-sequence star in Orion
Sigma Orionis is a blue main-sequence star in the constellation Orion. At 950 light years away, it is the 391st brightest star in the Earth's sky, where it shines at an apparent visual magnitude of 3.77.
Sigma Orionis (HIP 26549)
Sigma Orionis is a blue main-sequence star in the constellation Orion. At 950 light years away, it is the 391st brightest star in the Earth's sky, where it shines at an apparent visual magnitude of 3.77. Sigma Orionis is a multiple-star system. It is moving through the Galaxy at a speed of 30.6 km/s relative to the Sun and is part of the Orion Molecular Cloud and Collinder 70 and Sigma Orionis moving groups. Its projected Galactic orbit carries it between 24,300 and 26,400 light years from the center of the Galaxy. It came closest to the Sun 9.1 million years ago when it had brightened to magnitude 0.37 from a distance of 199 light years.
Sky position: RA 5h 38.7m, Dec -2° 36'
Common designations: Sigma Orionis, 48 Orionis, HIP 26549, HD 37468
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Brightest stars in Orion:
(list all)
| Rank | Mag. | Star |
| 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
| Rank | Mag. | Star |
| 16 | 4.06 | Omicron-2 Orionis |
| 17 | 4.09 | Phi-2 Orionis |
| 18 | 4.12 | Mu Orionis |
| 19 | 4.13 | 29 Orionis |
| 20 | 4.20 | A Orionis |
| 21 | 4.35 | Pi-2 Orionis |
| 22 | 4.39 | Phi-1 Orionis |
Hover over other bright stars to identify or click to jump.
Galactic Orbit of Sigma Orionis
(compared to the Sun)
E
ccentricity: 4.2% vs. 16.0%Angle φ : -70.2°vs. 26.0°
Semi-major axis : 7,772 pc vs. 8,686 pc
Semi-minor axis: 7,765 pc vs. 8,574 pc
Focus-to-center
: 325 pcvs. 1,388 pcSemilatus rectum : 7,758 pc vs. 8,464 pc
Perigalacticon: 7,446 pc vs. 7,297 pc
Apogalacticon
: 8,097 pcvs. 10,074 pcSome Tabulated XHIP Data for Sigma Orionis
(see also: SIMBAD)
Astrometry
2007A&A...474..653V
| Position | Proper Motion | |
| Right Ascension: | 84.68652211° ±1.46 mas | 4.61 ±0.88 mas/yr. |
| Declination: | -2.60006791° ±0.95 mas | -0.40 ±0.53 mas/yr. |
| Galactic Longitude: | 206.81632632° | 2.49 mas/yr. |
| Galactic Latitude: | -17.33600882° | 3.90 mas/yr. |
Parallax: 2.84 ± 0.91 mas
Spectrography
Spectral Type: O9.5V 2009A&A...501..297Z.
Radial Velocity: 29.90 ±1.60 km/s [B rating] 2007AN....328..889K.
Iron Abundance [Fe/H]:
n/a
Photometry
band
magnitude
Abs. Mag.
U
2.50
-4.82
B
3.58
-3.74
V
3.77
-3.55
R
I
4.02
-3.30
J
4.75
-2.57
H
4.64
-2.68
K
4.49
-2.83
B-V: -0.19 V-I: -0.25
Derivations
Heliocentric distance: 291.36 pc (fitted to cluster)
Galactocentric distance: 7,650 pc
Transverse velocity: 6.4 km/s
3D heliocentric position and motion:
|
toward: |
Galactic center | Galactic rotation | North Galactic Pole |
| Position ( X, Y, Z) | -248.2 pc | -125.5 pc | -86.8 pc |
| Velocity (U, V, W) | -25.4 km/s | -16.7 km/s | -3.8 km/s |