Delta Velorum (δ Velorum, abbreviated Delta Vel, δ Vel) is a
triple star system
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a ''star cluster'' or ''galaxy'', although, broadly speaking, ...
in the
southern constellation of
Vela, near the border with
Carina
Carina may refer to:
Places
Australia
* Carina, Queensland, a suburb in Brisbane
* Carina Heights, Queensland, a suburb in Brisbane
* Carina, Victoria, a locality in Mildura
Serbia
* Carina, Osečina, a village in the Kolubara District
...
, and is part of the
False Cross
An asterism is an observational astronomy, observed pattern or group of stars in the sky. Asterisms can be any identified pattern or group of stars, and therefore are a more general concept than the IAU designated constellations, formally defined ...
. Based on
parallax measurements, it is approximately from the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
. It is one of the stars that at times lies near the
south celestial pole due to
precession
Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In oth ...
.
δ Velorum consists of an
eclipsing binary
A binary star 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 using a telescope as separate stars, in w ...
, designated Delta Velorum A, and a more distant third companion, Delta Velorum B. δ Velorum A's two components are themselves designated Aa (officially named Alsephina , the traditional name for the entire system) and Ab.
Nomenclature
![Milky way - southern hemisphere contrast](https://upload.wikimedia.org/wikipedia/commons/e/e8/Milky_way_-_southern_hemisphere_contrast.jpg)
''δ Velorum'' (
Latinised to ''Delta Velorum'') is the system's
Bayer designation. The designations of the two constituents as ''Delta Velorum A'' and ''B'', and those of ''A'' components—''Delta Velorum Aa'' and ''Ab''—derive from the convention used by the
Washington Multiplicity Catalog
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a ''star cluster'' or ''galaxy'', although, broadly speaking, ...
(WMC) for multiple
star systems, and adopted by the
International Astronomical Union
The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...
(IAU).
Delta Velorum bore the traditional name ''Alsafinah'', which stems from the
Arabic
Arabic (, ' ; , ' or ) is a Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C. E.Watson; Walter ...
name ''al-safīnah'' meaning "the ship", referring to the
ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
constellation
Argo Navis
Argo Navis (the Ship Argo), or simply Argo, is one of the 48 Ptolemy's constellations, now a grouping of three IAU constellations. It is formerly a single large constellation in the southern sky. The genitive is "Argus Navis", abbreviated "Arg" ...
, the ship of the
Argonauts. It was first used in a 10th-century Arabic translation of the ''
Almagest'', written by the Greek astronomer
Ptolemy
Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importance ...
in the second century AD. Although the name originally referred to an entire constellation, it was assigned to this particular bright star at least as early as 1660, when it appeared in
Andreas Cellarius
Andreas Cellarius (–1665) was a Dutch–German cartographer and cosmographer best known for his 1660 ''Harmonia Macrocosmica'', a major star atlas.
Life
He was born in Neuhausen, and was educated in Heidelberg. The Protestant Cellarius m ...
's renowned ''
Harmonia Macrocosmica
The ''Harmonia Macrocosmica'' is a star atlas written by Andreas Cellarius and published in 1660 by Johannes Janssonius. The first part of the atlas contains copper plate prints depicting the world systems of Claudius Ptolemy, Nicolaus Coper ...
'', a magnificently illustrated 17th-century
Dutch
Dutch commonly refers to:
* Something of, from, or related to the Netherlands
* Dutch people ()
* Dutch language ()
Dutch may also refer to:
Places
* Dutch, West Virginia, a community in the United States
* Pennsylvania Dutch Country
People E ...
book about the
cosmos
The cosmos (, ) is another name for the Universe. Using the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity.
The cosmos, and understandings of the reasons for its existence and significance, are studied in ...
.
In 2016, the IAU organized a
Working Group on Star Names
The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...
(WGSN)
to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire
multiple systems.
[ It approved the name ''Alsephina'' for the component δ Velorum Aa on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.]
The False Cross
An asterism is an observational astronomy, observed pattern or group of stars in the sky. Asterisms can be any identified pattern or group of stars, and therefore are a more general concept than the IAU designated constellations, formally defined ...
is an asterism formed of Delta and Kappa 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 syst ...
along with Iota Carinae
Iota Carinae (ι Carinae, abbreviated Iota Car, ι Car), officially named Aspidiske , is a star in the southern constellation of Carina. With an apparent visual magnitude of 2.2, it is one of the brighter stars in the night sky.
Appe ...
and Epsilon Carinae
Epsilon Carinae (ε Carinae, abbreviated Epsilon Car, ε Car), officially named Avior , is a binary star in the southern constellation of Carina. At apparent magnitude +1.86 it is one of the brightest stars in the night sky, but is not v ...
. It is so called because it is sometimes mistaken for the Southern Cross
Crux () is a constellation of the southern sky that is centred on four bright stars in a cross-shaped asterism commonly known as the Southern Cross. It lies on the southern end of the Milky Way's visible band. The name ''Crux'' is Latin for ...
, causing errors in astronavigation
Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space (or on the surface o ...
.[
In ]Chinese
Chinese can refer to:
* Something related to China
* Chinese people, people of Chinese nationality, citizenship, and/or ethnicity
**''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation
** List of ethnic groups in China, people of ...
, (), meaning '' Celestial Earth God's Temple'', refers to an asterism consisting of Delta Velorum, Gamma2 Velorum, Kappa Velorum and b Velorum. Consequently, Delta Velorum itself is known as (), "the Third Star of Celestial Earth God's Temple". In a different Chinese view, this star appears in an asterism with the given name of ''Koo She'' (Chinese
Chinese can refer to:
* Something related to China
* Chinese people, people of Chinese nationality, citizenship, and/or ethnicity
**''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation
** List of ethnic groups in China, people of ...
: 弧矢, hú shǐ, "Bow and Arrow"), comprising Delta Velorum, Omega Carinae and stars from Canis Major.
Stellar system
Delta Velorum is a triple star system. The outer components, δ Velorum A and B, have a wide orbit with a 143-year period
Period may refer to:
Common uses
* Era, a length or span of time
* Full stop (or period), a punctuation mark
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (or rhetorical period), a concept ...
. The primary component A has an apparent magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...
of 2.00, while the secondary B is magnitude 5.54, with a combined magnitude measured at 1.96.[ As of 2013, the two stars were separated by 0.6", but they have an eccentric orbit and their average separation over the whole orbit is nearly 2".][
In 1978 the primary component was reported to be a spectroscopic binary in the Proceedings of the Australian Astronomical Observatory, and this was confirmed by the '' Hipparcos'' satellite.]
In 2000 it was announced that the inner components Aa and Ab form an eclipsing binary
A binary star 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 using a telescope as separate stars, in w ...
, having an orbital period of 45.15 days and an eccentricity
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-Centre (geometry), center, in geometry
* Eccentricity (g ...
of 0.230.[ The semi-major axis as their orbit corresponds to a mean separation of 90.61 AU.][ Delta Velorum is the brightest-known eclipsing binary, although ]Algol
ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the ...
has a deeper minimum and is easier to observe visually. Observations of variability in the Delta Velorum system were made independently by ground-based astronomers and the ''Galileo'' spaceprobe at Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...
. The inner pair were resolved using interferometry in 2007, and then using NACO adaptive optics
Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...
with the Very Large Telescope
The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m acro ...
. Photometry of the components of δ Velorum A gives apparent visual magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...
s of 2.33 and 3.44.[ The precise orbits allow a ]dynamical parallax
In astronomy, the distance to a visual binary star may be estimated from the masses of its two components, the size of their orbit, and the period of their orbit about one another. A dynamical parallax is an (annual) parallax which is computed fr ...
of to be derived, representing a distance of 25.1 parsecs.[
Another binary system is located at an angular separation of 69 ]arcseconds
A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The ...
from δ Velorum, sometimes referred to as δ Velorum C and D. The pair is composed of an 11th-magnitude star and a 13th-magnitude star, which are 6 arcseconds apart. The two stars, with approximate spectral type
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 ...
s of G8V and K0V, are expected to be more distant than δ Velorum and not physically associated.[
HD 76653 is a probable (96% chance) co-moving companion; the two have an estimated physical separation of with similar proper motions.][ Both are likely members of the Ursa Major Moving Group.][
]
Physical properties
The brightnesses of the three stars have been measured at visual and infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
wavelengths using adaptive optics. The physical properties implied by their surface brightness
In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on it ...
es and colour indices suggests spectral types of A2IV, A4V and F8V, respectively.[
More precise physical properties for the stars can be calculated using accurate orbital parameters. Both members of the spectroscopic binary Delta Velorum A are slightly ]evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
stars that are still on the main sequence. Component Aa has 2.5 times the mass of the Sun, 2.6 times the Sun's radius, and is radiating 56 times the luminosity of the Sun
The solar luminosity (), is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun.
One nominal ...
at an effective temperature of . Component Ab is only slightly smaller, with 2.4 times the Sun's mass and radius, with a luminosity of 47 times the Sun and an effective temperature of 9,370 K.[
Both stars are rotating rapidly and are significantly oblate, with polar radii smaller than their equatorial radii. ]Gravity darkening
Gravity darkening, also referred to as gravity brightening, is an astronomical phenomenon where the poles of a star are brighter than the equator, due to rapid rotation and oblate shape. When a star is oblate, it has a larger radius at its equa ...
results in their effective temperatures at the pole being higher. For component Aa, the polar radius and temperature are and 10,100 K, respectively, while the equatorial radius and temperature are and 9,700 K, respectively. For component Ab, the corresponding polar values are and 10,120 K, and the equatorial values are and 9,560 K.[ This results in the star being brighter when seen along their axes of rotation and less bright when observed at their equators. From Earth, the pair is observed nearly equatorially and the absolute visual magnitude is +0.02; from a different direction the absolute magnitude would be −0.138 or less.][
Delta Velorum B is a smaller ]main-sequence star
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hert ...
, with a mass of about , a temperature of 6,600 K, a radius of , and a bolometric luminosity of .[
]
Southern pole star
The south celestial pole
The north and south celestial poles are the two points in the sky where Earth's axis of rotation, indefinitely extended, intersects the celestial sphere. The north and south celestial poles appear permanently directly overhead to observers a ...
will pass close to Delta Velorum around 9000 AD because of precession
Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In oth ...
.[
]
References
External links
*
{{DEFAULTSORT:Delta Velorum
A-type main-sequence stars
F-type main-sequence stars
Algol variables
Triple star systems
Ursa Major Moving Group
Velorum, Delta
Vela (constellation)
CD-54 2351
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