Gamma Velorum is a quadruple

star system A star system or stellar system is a small number of stars that orbit each other, bound by gravity, gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally calle ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Vela. This name is the

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

for the star, which is Latinised from γ Velorum and abbreviated γ Vel. At a combined

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of +1.72, it is one of the brightest stars in the

night sky The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon. Natural light sources in a night sky include moonlig ...

, and contains by far the closest and brightest

Wolf–Rayet star Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectroscopy, spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very ...

. It has the traditional name Suhail al Muhlif and the modern name Regor , but neither is approved by the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

, making it the brightest star by apparent magnitude without an IAU approved name. The γ Velorum system includes a pair of stars separated by 41, each of which is also a spectroscopic binary system. γ² Velorum, the brighter of the visible pair, contains the Wolf–Rayet star and a

blue supergiant A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blu ...

, while γ¹ Velorum contains a

blue giant In astronomy, a blue giant is a hot star with a luminosity class of III (giant) or II (bright giant). In the standard Hertzsprung–Russell diagram, these stars lie above and to the right of the main sequence. The term applies to a variety of ...

and an unseen companion.

Distance

Gamma Velorum is close enough to have accurate parallax measurements as well as distance estimates by more indirect means. The ''

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions and distances of ...

'' parallax for γ² implies a distance of 342

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

s (pc). A

dynamical parallax In astronomy, the distance to a visual binary, visual binary star may be estimated from the masses of its two components, the angular size of their orbit, and the period of their orbit about one another. A dynamical parallax is an (annual) paralla ...

derived from calculations of the orbital parameters gives a value of 336 pc, similar to spectrophotometric derivations. A

VLTI The Very Large Telescope (VLT) is an astronomical facility operated since 1998 by the European Southern Observatory, located on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each equipped with a ...

-based

interferometry Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...

measurement of the distance gives a slightly larger value of . All these distances are somewhat less than the commonly assumed distance of 450 pc for the Vela OB2 association which is the closest grouping of young massive stars.

Stellar system

The Gamma Velorum system is composed of at least four stars. The brightest member, γ² Velorum or γ Velorum A, is a

spectroscopic binary A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

composed of a

spectral class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

O7.5 (), and a massive

(, originally ). The binary has an orbital period of 78.5 days and separation varying from 0.8 to 1.6

astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...

s. Both the Wolf–Rayet star and the blue supergiant are likely to end their lives as Type Ib supernovae; they are among 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, more luminous and also more massive. 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 In folklore, giants (from Ancient Greek: ''wiktionary:gigas, gigas'', cognate wiktionary:giga-, giga-) are beings of humanoid appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''gia ...

. It is separated from the Wolf–Rayet binary by 41.2″, easily resolved with

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held ...

. 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). γ² Velorum has also been revealed as a gamma-ray emitter on the basis of Fermi measurements showing a modulation fully compliant with its orbital period. This discovery allows this system to be part of the category of Particle-Accelerating Colliding-Wind Binaries (PACWB), binary systems made of massive stars whose winds collide, resulting in particle acceleration. 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 A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

from the A component. At 93.5 arcseconds is another binary star, an F0 star of magnitude +9.2. Gamma Velorum is associated with several hundred

pre-main-sequence star A pre-main-sequence star (also known as a PMS star and PMS object) is a star in the stage when it has not yet reached the main sequence. Earlier in its life, the object is a protostar that grows by acquiring mass from its surrounding envelope o ...

s within less than a degree. The ages of these stars would be at least 5 million years.

Etymology

The Arabic name is al Suhail al Muḥlīf. al Muhlif refers to ''the oath-taker'', and al Suhail is originally derived from a word meaning ''the plain''. Suhail is used for at least three other stars:

Canopus Canopus is the brightest star in the southern constellation of Carina (constellation), Carina and the list of brightest stars, second-brightest star in the night sky. It is also Bayer designation, designated α Carinae, which is Rom ...

λ Velorum ) Lambda Velorum (λ Velorum, abbreviated Lambda Vel, λ Vel), officially named Suhail , is a star in the southern constellation of Vela. With a mean apparent visual magnitude of 2.21, this is the third-brightest star in the constella ...

(al Suhail al Wazn) and

ζ Puppis Zeta Puppis (ζ Puppis, abbreviated Zeta Pup, ζ Pup), formally named Naos , is the brightest star in the constellation of Puppis. The spectral class of O4 means this is one of the hottest, and most luminous, stars vi ...

(Suhail Hadar).

Suhail ) Lambda Velorum (λ Velorum, abbreviated Lambda Vel, λ Vel), officially named Suhail , is a star in the southern constellation of Vela. With a mean apparent visual magnitude of 2.21, this is the third-brightest star in the constella ...

is also a common Arabic male first name. In

Chinese Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethnic ...

, (), meaning '' Celestial Earth God's Temple'', refers to an asterism consisting of γ² Velorum,

δ Velorum Delta Velorum (δ Velorum, abbreviated Delta Vel, δ Vel) is a Star system#Triple star systems, triple star system in the Southern celestial hemisphere, southern constellation of Vela (constellation), Vela, near the border with Carin ...

κ Velorum Kappa Velorum (κ Velorum, abbreviated Kappa Vel, κ Vel; proper name Markeb ) is a binary star system in the southern constellation of Vela. The two components are designated Kappa Velorum A and B. From parallax measurements, this sys ...

and b Velorum. Consequently, γ² Velorum itself is known as (), "the First Star of Celestial Earth God's Temple". The name Regor ("Roger" spelled in reverse) was invented as a practical joke by the

Apollo 1 Apollo 1, initially designated AS-204, was planned to be the first crewed mission of the Apollo program, the American undertaking to land the first man on the Moon. It was planned to launch on February 21, 1967, as the first low Earth orbital ...

astronaut

Gus Grissom Virgil Ivan "Gus" Grissom (April 3, 1926 – January 27, 1967) was an American engineer and pilot in the United States Air Force, as well as one of the original Mercury Seven selected by the NASA, National Aeronautics and Space Administration fo ...

for his fellow astronaut

Roger Chaffee Roger Bruce Chaffee (; February 15, 1935 – January 27, 1967) was an American naval officer, aviator and aeronautical engineer who was a NASA astronaut in the Apollo program. Chaffee was born in Grand Rapids, Michigan, where he became an Eag ...

.Apollo 15 Lunar Surface Journal
''Post-landing Activities''
commentary at 105:11:33 Due to the exotic nature of its spectrum (bright

emission line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used ...

s in lieu of dark

absorption line Absorption spectroscopy is spectroscopy that involves techniques that measure the absorption (electromagnetic radiation), absorption of electromagnetic radiation, as a function of frequency or wavelength, due to its interaction with a sample. Th ...

s) it is also dubbed the ''Spectral Gem of Southern Skies''.

References

{{DEFAULTSORT:Gamma Velorum O-type giants B-type giants Wolf–Rayet stars Spectroscopic binaries 6 Gum Nebula Vela (constellation) Velorum, Gamma 3207 Durchmusterung objects 068273 039953 Regor TIC objects Southern pole stars

Distance

Stellar system

Etymology

See also

References