Delta Velorum

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Template:Short description

δ Velorum
Template:Location mark
Location of δ Velorum (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
δ Vel A
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 1.95 - 2.43[2]
δ Vel B
Right ascension Template:RA[1]
Declination Template:DEC
Apparent magnitude (V) 5.54[3]
Characteristics
U−B Template:Engvar +0.07[4]
B−V Template:Engvar +0.04[4]
δ Vel A
Spectral type A1 Va(n)[5]
Variable type Algol[6]
δ Vel B
Spectral type F7.5V[7]
Astrometry
Radial velocity (Rv)+2.2[8] km/s
Proper motion (μ) RA: +28.99[9] mas/yr
Dec.: −103.35[9] mas/yr
Parallax (π)40.49±0.39 mas[9]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)0.02/3.60[10]
Orbit[7]
Primaryδ Vel A
Companionδ Vel B
Period (P)143.2 yr
Semi-major axis (a)1.996″
Eccentricity (e)0.475
Inclination (i)105.1°
Orbit[7]
Primaryδ Vel Aa
Companionδ Vel Ab
Period (P)45.1503 days
Semi-major axis (a)0.01651″
Eccentricity (e)0.287
Inclination (i)89.04°
Details
δ Vel Aa
Mass2.43[7] Template:Solar mass
Radius2.79–2.97[7] Template:Solar radius
Luminosity67[7] Template:Solar luminosity
Surface gravity (log g)3.78–3.90[7] cgs
Temperature9,440[7] K
Metallicity [Fe/H]−0.33[7] dex
Rotation1.05[7] days
Rotational velocity (v sin i)143.5[7] km/s
Age400[10] Myr
δ Vel Ab
Mass2.27[7] Template:Solar mass
Radius2.37–2.52[7] Template:Solar radius
Luminosity51[7] Template:Solar luminosity
Surface gravity (log g)3.99–4.10[7] cgs
Temperature9,830[7] K
Metallicity [Fe/H]−0.33[7] dex
Rotational velocity (v sin i)149.6[7] km/s
δ Vel B
Mass1.35–1.46[7] Template:Solar mass
Radius1.43[7] Template:Solar radius
Luminosity3.5[7] Template:Solar luminosity
Temperature6,600[7] K
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Alsephina, CD−54°1788, GCTP 2098.00, HD 74956, HIP 42913, HR 3485, SAO 236232, WDS 08447-5443
Database references
SIMBADdata

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Delta Velorum (δ Velorum, abbreviated Delta Vel, δ Vel) is a triple star system in the southern constellation of Vela, near the border with Carina, and is part of the False Cross. Based on parallax measurements, it is approximately Template:Convert from the Sun. It is one of the stars that at times lies near the south celestial pole due to precession.

δ Velorum consists of an eclipsing binary, 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 Template:IPAc-en, the traditional name for the entire system) and Ab.

Nomenclature

File:Milky way - southern hemisphere contrast.jpg
δ Velorum and the False Cross, lying across the Milky Way near the centre of this panorama

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 ATemplate:'s components—Delta Velorum Aa and Ab—derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[11]

Delta Velorum bore the traditional name Alsafinah, which stems from the Arabic name al-safīnah meaning "the ship", referring to the ancient Greek constellation Argo Navis, the ship of the Argonauts. It was first used in a 10th-century Arabic translation of the Almagest, written by the Greek astronomer Ptolemy 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's renowned Harmonia Macrocosmica, a magnificently illustrated 17th-century Dutch book about the cosmos.[12] In 2016, the IAU organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[14] 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.[15]

The False Cross is an asterism formed of Delta and Kappa Velorum along with Iota Carinae and Epsilon Carinae. It is so called because it is sometimes mistaken for the Southern Cross, causing errors in astronavigation.[16]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Celestial Earth God's Temple, refers to an asterism consisting of Delta Velorum, Gamma2 Velorum, Kappa Velorum and b Velorum.[17] Consequently, Delta Velorum itself is known as Script error: No such module "Lang". (Script error: No such module "Lang".), "the Third Star of Celestial Earth God's Temple".[18] In a different Chinese view, this star appears in an asterism with the given name of Koo She (Chinese: 弧矢, hú shǐ, "Bow and Arrow"), comprising Delta Velorum, Omega Carinae and stars from Canis Major.[19]

Stellar system

File:Del Vel Pos.svg
Relative positions and separations of components A, B, C and D of δ Velorum

Delta Velorum is a triple star system. The outer components, δ Velorum A and B, have a wide orbit with a 143-year period. The primary component A has an apparent magnitude of 2.00, while the secondary B is magnitude 5.54, with a combined magnitude measured at 1.96.[20] 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".[7]

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.[21]

File:DeltaVelLightCurve.png
A white-light light curve for Delta Velorum, adapted from Pribulla et al. (2011)[10]

In 2000 it was announced that the inner components Aa and Ab form an eclipsing binary, having an orbital period of 45.15 days and an eccentricity of 0.230.[10] The semi-major axis as their orbit corresponds to a mean separation of Template:Val.[22] Delta Velorum is the brightest eclipsing binary, although Algol 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.[21] The inner pair were resolved using interferometry in 2007, and then using NACO adaptive optics with the Very Large Telescope. Photometry of the components of δ Velorum A gives apparent visual magnitudes of 2.33 and 3.44.[3] The precise orbits allow a dynamical parallax of Template:Val to be derived, representing a distance of 25.1 parsecs.[7]

Another binary system is located at an angular separation of 69 arcseconds 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 types of G8V and K0V, are expected to be more distant than δ Velorum and not physically associated.[23]

HD 76653 is a probable (96% chance) co-moving companion; the two have an estimated physical separation of Template:Cvt with similar proper motions.[24] Both are likely members of the Ursa Major Moving Group.[25]

Physical properties

The brightnesses of the three stars have been measured at visual and infrared wavelengths using adaptive optics. The physical properties implied by their surface brightnesses and colour indices suggests spectral types of A2IV, A4V and F8V, respectively.[3]

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 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 at an effective temperature of Template:Val. 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.[10]

Both stars are rotating rapidly and are significantly oblate, with polar radii smaller than their equatorial radii. Gravity darkening results in their effective temperatures at the pole being higher. For component Aa, the polar radius and temperature are Template:Solar radius and 10,100 K, respectively, while the equatorial radius and temperature are Template:Solar radius and 9,700 K, respectively. For component Ab, the corresponding polar values are Template:Solar radius and 10,120 K, and the equatorial values are Template:Solar radius and 9,560 K.[7] 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.[10]

Delta Velorum B is a smaller main-sequence star, with a mass of about Template:Solar mass, a temperature of 6,600 K, a radius of Template:Solar radius, and a bolometric luminosity of Template:Solar luminosity.[7]

Southern pole star

Script error: No such module "Labelled list hatnote". The south celestial pole will pass close to Delta Velorum around 9000 AD because of precession.[26]

References

Template:Reflist

External links

Template:Sky

Template:Stars of Vela

Template:Authority control

  1. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named tycho
  2. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named vsx
  3. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named kervella
  4. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named clpl4_99
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aj132_1_161
  6. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named gcvs
  7. ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z Cite error: Invalid <ref> tag; no text was provided for refs named merand
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named wilson1953
  9. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named aaa474_2_653
  10. ↑ a b c d e f Cite error: Invalid <ref> tag; no text was provided for refs named aaa528_A21
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named planetnaming
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named iau1707
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named WGSN
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named TriRpt18
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named IAU-LSN
  16. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named moore
  17. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named zh
  18. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named lcsd
  19. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named hinkley63
  20. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named hr
  21. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Otero2000
  22. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named eker
  23. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named kellerer
  24. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Shaya2011
  25. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Fuhrmann2012
  26. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named JK
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