Omicron Hydrae
Omicron Hydrae (ο Hya) is the Bayer designation for a solitary star in the equatorial constellation Hydra. At one time it bore the Flamsteed designation 25 Crateris, but this is no longer used by astronomers so as to avoid confusion. With an apparent visual magnitude of 4.70, this star is visible to the naked eye. Based upon an annual parallax shift of 7.27 mas, it is located around 449 light years from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 11h 40m 12.78970s |
| Declination | −34° 44′ 40.7733″ |
| Apparent magnitude (V) | 4.70 |
| Characteristics | |
| Spectral type | B9 V |
| U−B color index | −0.20 |
| B−V color index | −0.08 |
| Astrometry | |
| Radial velocity (Rv) | +5.9 km/s |
| Proper motion (μ) | RA: −43.24 mas/yr Dec.: −1.61 mas/yr |
| Parallax (π) | 7.27 ± 0.16 mas |
| Distance | 449 ± 10 ly (138 ± 3 pc) |
| Absolute magnitude (MV) | −0.99 |
| Details | |
| Mass | 3.56±0.04 M☉ |
| Luminosity | 309 L☉ |
| Temperature | 10,495 K |
| Rotational velocity (v sin i) | 160 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a B-type main sequence star with a stellar classification of B9 V. It has completed an estimated 98.4%±1.1% of its lifetime on the main sequence. With 3.56 times the mass of the Sun, it radiates 309 times the Sun's luminosity from its outer atmosphere at an effective temperature of 10,495 K. The rate of spin is relatively high, with a projected rotational velocity of 160 km/s.