Omega Carinae, Latinized from ω Carinae, is a star in the constellation Carina. With a declination greater than 70 degrees south of the celestial equator, it is the most southerly of the bright stars of Carina (third-magnitude or brighter), and it is part of a southern asterism known as the Diamond Cross. This star has an apparent visual magnitude of 3.3 and is located at a distance of about 342 light-years (105 parsecs) from Earth.
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Carina |
Right ascension | 10h 13m 44.21739s[1] |
Declination | –70° 02′ 16.4563″[1] |
Apparent magnitude (V) | 3.29[2] |
Characteristics | |
Spectral type | B8 IIIe[3] |
U−B color index | –0.285[4] |
B−V color index | –0.083[4] |
Astrometry | |
Radial velocity (Rv) | +7.0[2] km/s |
Proper motion (μ) | RA: -36.01[1] mas/yr Dec.: +7.09[1] mas/yr |
Parallax (π) | 9.54 ± 0.09 mas[1] |
Distance | 342 ± 3 ly (104.8 ± 1.0 pc) |
Absolute magnitude (MV) | −1.81[5] |
Details | |
Radius | 7.20±0.14[6] R☉ |
Luminosity | 918[7] L☉ |
Surface gravity (log g) | 3.51[7] cgs |
Temperature | 11,630[7] K |
Rotational velocity (v sin i) | 240[7] km/s |
Other designations | |
Database references | |
SIMBAD | data |
Omega Carinae has a stellar classification of B8 IIIe,[3] which places it in the category of Be stars, that display emission lines of hydrogen their spectrum. Omega Carinae is a shell star,[3] having a circumstellar disk of gas surrounding its equator. The luminosity class of III indicates it has evolved into a giant star, having exhausted the hydrogen at its core and left the main sequence. The effective temperature of 11,630 K[7] in its outer envelope is what gives this star the blue-white hue that is characteristic of B-type stars.
This star is rotating rapidly with a projected rotational velocity of 240 km/s,[7] which gives a lower limit to the star's azimuthal velocity along the equator. The critical equatorial velocity, at which the star would begin to break up, is 320 km s−1. The star's axis of rotation is inclined by an estimated angle of 70.8° to the line of sight from the Earth.[9]
In the next 7500 years, the south Celestial pole will pass close to this star (AD 5800) and then I Carinae.[10]
In Chinese, 南船 (Nán Chuán), meaning Southern Boat, refers to an asterism consisting of ω Carinae, V337 Carinae, PP Carinae, θ Carinae and β Carinae .[11] Consequently, ω Carinae itself is known as 南船四 (Nán Chuán sì, English: the Fourth Star of Southern Boat.)[12]