Epoch J2000 Equinox J2000
|Right ascension||09h 47m 06.12170s|
|Declination||–65° 04′ 19.2267″|
|Apparent magnitude (V)||2.97 (+3.08/+6.25)|
|Spectral type||A8 Ib + B7 III|
|U−B color index||+0.13|
|B−V color index||+0.27|
|Radial velocity (Rv)||+14 km/s|
|Proper motion (μ)||RA: –11.51 mas/yr
Dec.: +4.71 mas/yr
|Parallax (π)||2.27 ± 0.28 mas|
|Distance||approx. 1,400 ly
(approx. 440 pc)
|Absolute magnitude (MV)||−5.56|
|υ Car A|
|Surface gravity (log g)||1.1 ± 0.3 cgs|
|Temperature||7,600 ± 350 K|
|Age||1.2 × 107 years|
|υ Car B|
|Surface gravity (log g)||3.3 ± 0.1 cgs|
|Temperature||23,000 ± 1600 K|
Upsilon Carinae (υ Car, υ Carinae) is a double star in the southern constellation of Carina. It is part of the Diamond Cross asterism in southern Carina. The Upsilon Carinae system has a combined apparent magnitude of +2.97 and is approximately 1,400 light years (440 parsecs) from Earth.
In Chinese, 海石 (Hǎi Dàn), meaning Sea Rock, refers to an asterism consisting of υ Carinae, ε Carinae, ι Carinae, HD 83183 and HD 84810. Consequently, υ Carinae itself is known as 海石五 (Hǎi Dàn wǔ, English: the Fifth Star of Sea Rock.)
The primary component, υ Carinae A, has a stellar classification of A8 Ib, making it a supergiant star that has exhausted the hydrogen at its core and evolved away from its brief main sequence lifetime as an O9 V star. With an apparent magnitude of +3.08, it has an effective temperature of about 7,600 K, giving it a white hue. The companion, υ Carinae B, is a giant star with a classification of B7 III, although Mandrini and Niemela (1986) suggested it may be a subgiant star with a classification of B4–5 IV. The outer envelope of this star has an effective temperature of around 23,000 K, resulting in the blue-white hue of a B-type star.
The two stars have an angular separation of 5.030 arcseconds. As a binary star system, they would have an estimated orbital period of at least 19,500 years and a present day separation of around 2,000 Astronomical Units. This system is roughly 12 million years old.
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