Delta Velorum

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Delta Velorum A/B
Diagram showing star positions and boundaries of the Vela constellation and its surroundings
Cercle rouge 100%.svg

Location of δ Velorum (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 44m 42.22658s[1]
Declination −54° 42′ 31.7493″[1]
Apparent magnitude (V) 1.96[2] (1.97/5.55)[3]
Spectral type A1 Va(n)[4] + F2-F5[3]
U−B color index +0.07[2]
B−V color index +0.04[2]
Variable type Eclipsing binary
Radial velocity (Rv) +2.2[5] km/s
Proper motion (μ) RA: +28.99[1] mas/yr
Dec.: −103.35[1] mas/yr
Parallax (π) 40.49 ± 0.39[1] mas
Distance 80.6 ± 0.8 ly
(24.7 ± 0.2 pc)
Absolute magnitude (MV) 0.02/3.60[3]
Mass 2.53/2.37[3] M
Radius 2.643/2.363[3] R
Luminosity 56.3/47.1[3] L
Surface gravity (log g) 3.79[4] cgs
Temperature 9,470/9,370[3] K
Rotational velocity (v sin i) 150[6] km/s
Age 400 million[3] years
Mass 1.5[3] M
Other designations
CD −54° 1788, GCTP 2098.00, Gl 321.3 A/B, HD 74956, HIP 42913, HR 3485, SAO 236232.
Database references

Delta Velorum (δ Vel, δ Velorum) is a star system in the southern constellation Vela, near the border with Carina. From parallax measurements, it is approximately 80.6 light-years (24.7 parsecs) from Earth. This star is sometimes given the name Koo She, Chinese for 'Bow and Arrows', along with ω Velorum and stars in Canis Major.[7]


Delta Velorum is a triple star system. The outward components A and B have a wide orbit with a 142 year orbital period. The primary component A has an apparent magnitude of 1.97, while the secondary component B is magnitude 5.55. In 1978 the primary component was reported to be a spectroscopic binary in the Proceeding of the Australian Astronomical observatory, and this was confirmed by the Hipparcos satellite. Observations of variability in the δ Velorum system were made independently by ground-based astronomers and the Galileo spaceprobe at Jupiter.[8]

In 2000 it was announced that the components Aa and Ab form an eclipsing binary, having an orbital period of 45.15 days and an eccentricity of 0.230.[3] Delta Velorum is the brightest known eclipsing binary, although Algol has a deeper minimum and is easier to observe visually. Only the primary component δ Velorum A is sufficiently bright to explain such variation.

Both members of the spectroscopic binary δ Vel A are evolved stars that have left 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 9,470. 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. The two stars are spinning rapidly and are about 400 million years old.[3]

Because of precession, δ Velorum will be the south polar star around 9000 AD.[9]

A second binary system is located at an angular separation of 69 arcseconds. It is composed of an 11th magnitude and 13th magnitude pair, which are 6 arcseconds apart.


The Chinese name Koo She 弧矢 (Mandarin húshǐ) "Bow and Arrow", originally assigned for some[which?] stars among Canis Major, Puppis, and Vela, was introduced by Robson[who?] for this star.[citation needed]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99): 99, Bibcode:1966CoLPL...4...99J 
  3. ^ a b c d e f g h i j k Pribulla, T. et al. (April 2011), "The nearby eclipsing stellar system δ Velorum. II. First reliable orbit for the eclipsing pair", Astronomy & Astrophysics 528: A21, arXiv:1012.5886, Bibcode:2011A&A...528A..21P, doi:10.1051/0004-6361/201016227 
  4. ^ a b Gray, R. O. et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637 
  5. ^ Wilson, Ralph Elmer (1953), "General catalogue of stellar radial velocities", Washington (Carnegie Institution of Washington), Bibcode:1953QB901.W495..... 
  6. ^ Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224 
  7. ^ Allen, Richard Hinckley (1963), Star Names: Their Lore and Meaning (Revised ed.), New York: Dover Publications, p. 73, ISBN 0-486-21079-0 
  8. ^ Otero, Fieseler & Lloyd; Fieseler, Paul D.; Lloyd, Christopher (2000), "Delta Velorum is an Eclisping Binary", Information Bulletin on Variable Stars (IBVS 4999) 4999: 1, Bibcode:2000IBVS.4999....1O 
  9. ^ Kaler, James B., "Delta Velorum", Stars (University of Illinois), retrieved 2012-08-04