BO Carinae
Star in the constellation Carina
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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 ICRS | |
|---|---|
| Constellation | Carina |
| Right ascension | 10h 46m 50.658s[1] |
| Declination | 59° 29′ 19.32″[1] |
| Apparent magnitude (V) | 7.18 - 8.50[2] |
| Characteristics | |
| Spectral type | M4 Ib[2] |
| Variable type | Lc[2] |
| Astrometry | |
| Proper motion (μ) | RA: −7.334±0.027[1] mas/yr Dec.: −1.420±0.028[1] mas/yr |
| Parallax (π) | 0.6020±0.0259 mas[1] |
| 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.[2][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]