BO Carinae
Star in the constellation Carina From Wikipedia, the free encyclopedia
BO Carinae, also known as HD 93420, is an irregular variable star in the constellation Carina.
![]() BO Carinae is the brightest red star, towards upper left, in this image of the Carina Nebula. Credit: ESO | |
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Carina |
Right ascension | 10h 46m 00.53s |
Declination | 59° 29′ 19.5″ |
Apparent magnitude (V) | 7.18 - 8.50[1] |
Characteristics | |
Spectral type | M4 Ib[1] |
Variable type | Lc[1] |
Astrometry | |
Proper motion (μ) | RA: −7.334±0.027[2] mas/yr Dec.: −1.420±0.028[2] mas/yr |
Parallax (π) | 0.6020±0.0259 mas[2] |
Distance | 5,400 ± 200 ly (1,660 ± 70 pc) |
Absolute magnitude (MV) | –5.53[3] |
Details | |
Radius | 790[3] R☉ |
Luminosity | 78,000[3] L☉ |
Temperature | 3,525[3] K |
Other designations | |
BO Car, IDS 10419-5858, IRAS 10438-5913, 2MASS J10455065-5929193, AAVSO 1042-58, SAO 238447, CD-58 3547, HD 93420 | |
Database references | |
SIMBAD | data |
BO Car has a maximum apparent magnitude of +7.18. Its distance and membership is uncertain, but its possible membership to the star cluster Trumpler 15 allows a distance estimate of approximately 2,500 parsecs (8,150 light-years).[4][5] The Gaia Data Release 2 parallax of 0.73±0.08 mas suggests a closer distance, but the value is considered unreliable due to excess astrometric noise.[6]
BO Car is a red supergiant of spectral type M4Ib with an effective temperature of 3,525 K, a radius of 790 solar radii. Its bolometric luminosity is 78,000 L☉.[3] Mass-loss is on the order of 0.3×10−9 solar masses per year.[5]

In 1919, William Matthew Worssell of the Union Observatory announced that the star, then known as CPD-58 2683, is a variable star.[8] It was given its variable star designation, BO Carinae, in 1921.[9] Billed as an irregular variable like TZ Cassiopeiae or V528 Carinae; its apparent brightness fluctuates between magnitude +7.18 and +8.50 without clear periodicity.[1][10] Some observers have found BO Car not to be variable,[11] but more extensive studies find small amplitude variations with a possible period of 145 days.[12]
Multiple star catalogues list an 11th-magnitude star as a companion to BO Car. The separation was 14.2″ in 2015, and slowly increasing.[13] The companion is a distant blue giant.[14]
See also
References
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