Delta Velorum

Delta Velorum A/B

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]
Characteristics
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
Astrometry
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]
Details
Aa/Ab
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
B
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
SIMBAD	data

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]

Components

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.

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.^{[citation needed]}

References