Kappa Hydrae
κ Hydrae, Latinised as Kappa Hydrae, is a solitary star in the equatorial constellation of Hydra. Its apparent visual magnitude is 5.06, which is bright enough to be faintly visible to the naked eye. The distance to this star is around 135 pc (440 ly), based upon an annual parallax shift of 7.48 mas. It may be a variable star, meaning it undergoes repeated fluctuations in brightness by at least 0.1 magnitude.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 09h 40m 18.36496s |
| Declination | −14° 19′ 56.2675″ |
| Apparent magnitude (V) | 5.06 |
| Characteristics | |
| Spectral type | B4 IV/V |
| U−B color index | −0.57 |
| B−V color index | −0.15 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | 20.6±2.0 km/s |
| Proper motion (μ) | RA: −23.41 mas/yr Dec.: −21.10 mas/yr |
| Parallax (π) | 7.48 ± 0.30 mas |
| Distance | 440 ± 20 ly (134 ± 5 pc) |
| Absolute magnitude (MV) | −0.98 |
| Details | |
| Mass | 5.0±0.1 M☉ |
| Radius | 3.4 R☉ |
| Luminosity | 328 L☉ |
| Temperature | 16,150±920 K |
| Rotational velocity (v sin i) | 115.0 km/s |
| Age | 30.7±3.3 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is an evolving B-type star with a stellar classification of B4 IV/V, having a luminosity class intermediate between a subgiant and a giant star. It has an estimated five times the mass of the Sun and 3.4 times the Sun's radius. Kappa Hydrae has a high rate of spin with a projected rotational velocity of 115.0 km/s, and is only about 31 million years old. The star radiates 328 times the solar luminosity from its outer atmosphere at an effective temperature of 16,150 K.