Chi Carinae

Not to be confused with X Carinae.
Chi Carinae
Diagram showing star positions and boundaries of the Carina constellation and its surroundings
Location of χ Carinae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Carina
Right ascension 07h 56m 46.690s[1]
Declination −52° 58′ 55.95″[1]
Apparent magnitude (V) +3.6[1]
Characteristics
Spectral type B3IVp[1]
U−B color index −0.670[2]
B−V color index −0.182[2]
Variable type None[3]
Astrometry
Radial velocity (Rv)+19.4[4] km/s
Proper motion (μ) RA: −28.68[5] mas/yr
Dec.: +19.71[5] mas/yr
Parallax (π)7.17 ± 0.47 mas[5]
Distance450 ± 30 ly
(139 ± 9 pc)
Absolute magnitude (MV)−2.25[6]
Details
Mass7.0 ± 0.1[7] M☉
Radius5.5[8] R☉
Luminosity2,266[6] L☉
Surface gravity (log g)3.5[9] cgs
Temperature17,200[9] K
Rotational velocity (v sin i)110[10] km/s
Age39.8 ± 4.7[7] Myr
Other designations
χ Car, CPD–52° 1343, FK5 303, HD 65575, HR 3117, HIP 38827, SAO 235635[11]
Database references
SIMBADdata

Chi Carinae, Latinised from χ Carinae (US: /kaɪ kəˈraɪniː/),[12] is a star in the southern constellation of Carina. It is a third-magnitude[2] star and is one of the brighter members of the constellation. The distance to the star can be determined directly through parallax measurements, yielding an estimate of roughly 450 light-years (140 parsecs) with a 6.7% margin of error.[5] This star is a suspected astrometric binary,[13] although nothing is known about the companion.[14]

This is a massive star, with about seven times the mass of the Sun.[7] It is about 40[7] million years old and rotating rapidly; the projected rotational velocity has been measured as high as 110 km s−1.[10] The spectrum of this star matches a stellar classification of B3 IV,[15] with the luminosity class of IV indicating this is likely a subgiant star that has nearly exhausted the supply of hydrogen at its core and is in the process of evolving into a giant star.

In 1969, Chi Carinae was classified as chemically peculiar Ap star[16] because its absorption lines of silicon appeared unusually strong relative to the lines for helium. However, subsequent examination in the ultraviolet band showed the silicon bands were as expected and it was determined the spectra is normal for a star of its type. There is no indication of variability in the star's spectrum.[7] Observation during the Hipparcos mission showed no photometric variability down to a limit of ±0.003 magnitude. For this reason, the star has been ruled out as a Beta Cephei-type variable star.[3]

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