Theta Carinae
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Carina |
| Right ascension | 10h 42m 57.40197s |
| Declination | −64° 23′ 40.0208″ |
| Apparent magnitude (V) | 2.76 |
| Characteristics | |
| Evolutionary stage | Blue straggler |
| Spectral type | B0.5 Vp |
| U−B color index | −1.00 |
| B−V color index | −0.22 |
| Astrometry | |
| Radial velocity (Rv) | +24 km/s |
| Proper motion (μ) | RA: −18.36 mas/yr Dec.: +12.03 mas/yr |
| Parallax (π) | 7.16±0.21 mas |
| Distance | 460 ± 10 ly (140 ± 4 pc) |
| Absolute magnitude (MV) | −3.10 |
| Orbit | |
| Period (P) | 2.20288±0.00001 d |
| Eccentricity (e) | 0.129±0.002 |
| Argument of periastron (ω) (secondary) | 81.8±1.7° |
| Semi-amplitude (K1) (primary) | 18.93±0.05 km/s |
| Details | |
| θ Car A | |
| Mass | 14.9±0.4 M☉ |
| Radius | 5.1 R☉ |
| Luminosity | 14,500±1,000 L☉ |
| Surface gravity (log g) | 4.20 cgs |
| Temperature | 31,000±1,000 K |
| Rotational velocity (v sin i) | 108±3 km/s |
| Age | 35–46 Myr |
| Other designations | |
| θ Car, CPD−63°1599, FK5 406, HD 93030, HIP 52419, HR 4199, SAO 251083 | |
| Database references | |
| SIMBAD | data |
Theta Carinae is a binary star system in the southern constellation of Carina. Its name is a Bayer designation and is Latinized from θ Carinae, and abbreviated Theta Car or θ Car. With an apparent visual magnitude of 2.76, it is the brightest star in the open star cluster IC 2602, or the Southern Pleiades. It marks the northeastern end of the Diamond Cross asterism. Parallax measurements from the Hipparcos mission place this star at a distance of about 460 light-years (140 parsecs) from Earth.
In most versions of its asterism, the neighbouring bright stars, thus plotted along the imaginary hull forming Carina are Omega Carinae which is approximately 120 light years closer and PP (also known as p) Carinae, of a similar distance to Theta.