Delta Velorum

Delta Velorum A/B

Observation data Epoch J2000      Equinox J2000
Constellation	Vela
Right ascension	08h 44m 42.2s
Declination	−54° 42′ 30″
Apparent magnitude (V)	1.95 (2.03/5.1)
Characteristics
Spectral type	A1 V/G0 V
U−B color index	0.06
B−V color index	0.04
Variable type	Eclipsing binary
Astrometry
Radial velocity (Rv)	+2.2 km/s
Proper motion (μ)	RA: 28.78 mas/yr Dec.: −104.14 mas/yr
Parallax (π)	40.90 ± 0.38 mas
Distance	79.7 ± 0.7 ly (24.4 ± 0.2 pc)
Absolute magnitude (MV)	−0.01 (0.05/3.51)
Other designations
Gl 321.3 A/B, HR 3485, CD -54°1788, HD 74956, GCTP 2098.00, SAO 236232, GC 12069, CCDM 08448-5442, HIP 42913.
Database references
SIMBAD	data

Delta Velorum (δ Vel, δ Velorum) is a star system in the constellation Vela. It is approximately 79.7 light years from Earth. It is sometimes given the name Koo She, Chinese for 'Bow and Arrows', along with ω Velorum and stars in Canis Major.^[1]

Components

The system appears to be composed of two sets of binary stars. The brightest of the four stars, δ Velorum A, is a white A-type main sequence dwarf with an apparent magnitude of +2.02. Its binary companion, δ Velorum B, has a magnitude of +5.1 and is separated from the A component by 2.6 arcseconds.

The second binary system is 69 arcseconds away. It is composed of the 11th magnitude δ Velorum C and the 13th magnitude δ Velorum D, which are 6 arcseconds apart.

In 1978 the principal 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.^[2] The star varies by about 30% every 45 days. Delta Velorum is the brightest known eclipsing binary, although Algol has a deeper minimum and is easier to observe visually. Only the principal component δ Velorum A is sufficiently bright to explain such variation. The system is now believed to consist of six stars: an eclipsing binary with nearby companions Aa and B, and two more distant stars, C and D.

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

Etymology

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

References

1. ^ Allen, Richard Hinckley (1963). Star Names: Their Lore and Meaning (Revised edition ed.). New York: Dover Publications. p. 73. ISBN 0486210790. 
2. ^ Otero, Fieseler & Lloyd (2000). Delta Velorum is an Eclisping Binary. IBVS 4999. [1]