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Proper NameNone
Bayer DesignationSigma Orionis
Flamsteed Number48 Orionis
HR (BSC)1931
Right Ascension5h 38m 45s
Declination-2° 36' 0"
Distancec.1,100 light years
c.300 parsecs
MagnitudeApparent: +3.79
Absolute: -3.80
Spectral ClassO9.5V Blue-white main sequence star
Optimum VisibilityDecember / January
NotesA complex multiple system with an unusually large number of component stars. At the heart of the system is a binary circled by a third star in a relatively close orbit, and beyond this grouping there are at least three further companions following orbits progressively more distant from the central triplet.

A star system to the south of Orion's Belt, close to Alnitak (the Belt's eastern star) in the sky. It is a young system, having recently formed on the fringes of the Orion Molecular Cloud. The primary belongs to the O-type spectral classification, suggesting a surface temperature of up to 50,000 Kelvin. There are a multiple young stars in the Sigma Orionis system, and it can be compared with the Trapezium complex that lies nearby in the Orion Nebula.

Visible in the far east (left) of this image is the dark shape of the Horsehead Nebula, while the bright light of Alnitak in Orion's Belt can be seen shining on the northern edge of the frame. Imagery provided by Aladin sky atlas


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