Gamma Velorum (γ Vel, γ Velorum) is a multiple star system in the constellation Vela. At a combined magnitude +1.7, it is one of the brightest stars in the night sky, and contains the closest and brightest Wolf-Rayet star. It has the traditional name Regor, but is not approved by the International Astronomical Union. "Regor" is backwards for "Roger", in honor of the astronaut Roger Chaffee, who died in a fire.
The γ Velorum system includes a pair of stars separated by 41", each of which is also a spectroscopic binary star. γ2 Velorum, the brighter of the visible pair, contains a Wolf-Rayet star and a blue supergiant, while γ1 Velorum contains a w:blue giant and an unseen companion star.
The Gamma Velorum system is composed of at least four stars. The brightest member, γ² Velorum or γ Velorum A, is a spectroscopic binary composed of a blue supergiant of spectral class O7.5 (~30 M☉), and a massive Wolf-Rayet star (~9 M☉, originally ~35 M☉). The binary has an orbital period of 78.5 days and separation varying from 0.8 to 1.6 astronomical units. The Wolf-Rayet star is likely to end its life in a Type Ib supernova explosion; it is one of the nearest supernova candidates to the Sun. The Wolf Rayet star has traditionally been regarded as the primary since its emission lines dominate the spectrum, but the O star is visually brighter and also more luminous. For clarity, the components are now often referred to as WR and O.
The bright (apparent magnitude +4.2) γ¹ Velorum or γ Velorum B, is a spectroscopic binary with a period of 1.48 days. Only the primary is detected and it is a blue-white giant. It is separated from the Wolf-Rayet binary by 41.2", easily resolved with binoculars. The pair are too close to be separated without optical assistance, and they appear to the naked eye as a single star of apparent magnitude 1.72 (at the average brightness of γ2 of 1.83).
Gamma Velorum has several fainter companions that share a common motion and are likely to be members of the Vela OB2 association. The magnitude +7.3 CD-46 3848 is a white F0 star at is 62.3 arcseconds from the A component. At 93.5 arcseconds is another binary star, an F0 star of magnitude +9.2.
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