Gamma Velorum

From Wikipedia, the free encyclopedia

**Gamma² Velorum A/B**
Observation data Epoch J2000
Constellation (pronunciation)	Vela
Right ascension	08^h 09^m 32.0^s
Declination	−47° 20′ 12.0″
Apparent magnitude (V)	1.78/4.27
Characteristics
Spectral type	WC8 / O7.5e
U-B color index	−0.99
B-V color index	−0.22
Variable type	Wolf-Rayet
Astrometry
Radial velocity (R_v)	35 km/s
Proper motion (μ)	RA: −5.93 mas/yr Dec.: 9.90 mas/yr
Parallax (π)	3.88 ± 0.53 mas
Distance	approx. 800 ly (approx. 260 pc)
Absolute magnitude (M_V)	−5.31/−2.79
Other designations
Regor, Suhail, Suhail Al-Muhlif, HR 3207, CD −46°3846/3847, HD 68273, SAO 219504, FK5 309, GC 11105, CCDM 08095-4721, HIP 39953.
Database references
SIMBAD	data

Gamma Velorum (γ Vel/γ Velorum) is a star system in the constellation Vela. At magnitude +1.7, it is one of the brightest stars in the nighttime sky. It has the traditional names Suhail or Al Suhail al-Muhlif (confusingly, the name Suhail can also apply to other stars such as Lambda Velorum). It also has a more modern popular name Regor, which was invented as a practical joke by the Apollo 1 astronaut Gus Grissom for his fellow astronaut Roger Chaffee. Due to the exotic nature of its spectrum (bright emission lines in lieu of dark absorption lines) it is also dubbed the Spectral Gem of Southern Skies.^[1] The Gamma Velorum system is composed of at least six stars. The brightest member, γ² Velorum or γ Velorum A, is actually a spectroscopic binary composed of a blue supergiant of spectral class O9 (30 M_☉), and a massive Wolf-Rayet star, the heaviest known (10 M_☉, originally approx. 40 M_☉). The binary has an orbital period of 78.5 days and separation of 1 AU. Its nearest companion, the bright (apparent magnitude +4.2) γ¹ Velorum or γ Velorum B, is a blue-white B-type subgiant. It is separated from the Wolf-Rayet binary by 41.2", and the separation can easily be resolved with binoculars.

Gamma Velorum has several fainter companions. The magnitude +8.5 γ Velorum C, a white A-type star, is 62.3 arcseconds from the A component. At 93.5 arcseconds is the system's second binary star, γ Velorum D and E. The D component is another A-type star which has a magnitude of +9.4. Its companion is a 13th magnitude star, separated by 1.8 arcseconds.

[edit] Etymology

The medieval name Suhail (Al Suhail, Alsuhail, Suhail al Muhlif, Muliphein) is short for the Arabic سهيل المحلف suhayl al-muħlif "The glorious (star) of the oath".