Omega Carinae
Star in the constellation Carina
From Wikipedia, the free encyclopedia
Omega Carinae is a star in the constellation Carina. Its name is a Bayer designation that is Latinized from ω Carinae, and abbreviated Omega Car or ω Car. 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 naked eye 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 ICRS | |
|---|---|
| Constellation | Carina[1] |
| Right ascension | 10h 13m 44.21739s[2] |
| Declination | −70° 02′ 16.4563″[2] |
| Apparent magnitude (V) | 3.29[3] |
| Characteristics | |
| Spectral type | B8 IIIe[4] |
| U−B color index | −0.285[5] |
| B−V color index | −0.083[5] |
| Astrometry | |
| Radial velocity (Rv) | +7.0[3] km/s |
| Proper motion (μ) | RA: −36.01 mas/yr[2] Dec.: +7.09 mas/yr[2] |
| Parallax (π) | 9.54±0.09 mas[2] |
| Distance | 342 ± 3 ly (104.8 ± 1.0 pc) |
| Absolute magnitude (MV) | −1.81[1] |
| Details | |
| Mass | 4.9[6] M☉ |
| Radius | 7.20±0.14[7] R☉ |
| Luminosity | 918[8] L☉ |
| Surface gravity (log g) | 3.51[8] cgs |
| Temperature | 11,630[8] K |
| Rotational velocity (v sin i) | 240[8] km/s |
| Other designations | |
| ω Car, CD−69°1178, FK5 385, HD 89080, HIP 50099, HR 4037, SAO 250885[9] | |
| Database references | |
| SIMBAD | data |
Properties
Omega Carinae has a stellar classification of B8 IIIe,[4] which places it in the category of Be stars, that display emission lines of hydrogen their spectrum. Omega Carinae is a shell star,[4] 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[8] 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,[8] 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.[10]
In the next 7500 years, the south Celestial pole will pass close to this star (AD 5800) and then I Carinae.[11]
In culture
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 .[12] Consequently, ω Carinae itself is known as 南船四 (Nán Chuán sì, English: the Fourth Star of Southern Boat.)[13]