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Delta Velorum (δ Vel, δ Velorum) is a star system in the southern constellation Vela, near the border with Carina. Based on parallax measurements, it is approximately from Earth. This star appears in an asterism with the given name of Koo She, Chinese for 'Bow and Arrows', comprising δ Velorum and ω Velorum.〔 The south celestial pole will pass close to δ Velorum around 9000 AD because of precession. == 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 1.99, while the secondary component B is magnitude 5.57, with a combined magnitude measured at 1.96. 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.〔 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.〔 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.〔 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Delta Velorum」の詳細全文を読む スポンサード リンク
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