  | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 09h 05m 58.36642s[1] |
| Declination | +05° 05′ 32.3360″[1] |
| Apparent magnitude (V) | 5.00[2] |
| Characteristics | |
| Evolutionary stage | horizontal branch[3] |
| Spectral type | K2 II-III[4] |
| U−Bcolor index | +1.22[2] |
| B−Vcolor index | +1.22[2] |
| Astrometry | |
| Radial velocity (Rv) | +24.3±0.8[5] km/s |
| Proper motion (μ) | RA: −19.58[1]mas/yr Dec.: −11.07[1]mas/yr |
| Parallax (π) | 3.64±0.31 mas[1] |
| Distance | 900 ± 80 ly (270 ± 20 pc) |
| Absolute magnitude (MV) | −2.19[6] |
| Details[3] | |
| Mass | 4.32±0.37 M☉ |
| Radius | 48.49±5.55 R☉ |
| Luminosity | 944.3±178.3 L☉ |
| Surface gravity (log g) | 1.74±0.12 cgs |
| Temperature | 4,789[7] K |
| Metallicity[Fe/H] | −0.12±0.10 dex |
| Rotational velocity (v sin i) | 2.3[8] km/s |
| Age | 180±70 Myr |
| Other designations | |
| ω Hya,18 Hydrae,BD+05°2116,HD 77996,HIP 44659,HR 3613,SAO 117420[9] | |
| Database references | |
| SIMBAD | data |
Omega Hydrae,Latinised fromω Hydrae, is a golden-huedstar in theequatorialconstellation ofHydra, located to the west-southwest of the brighter starZeta Hydrae.[10] Based upon an annualparallax shift of just 3.64 mas as seen from Earth, it is located roughly 900 light-years from theSun. It is faintly visible to the naked eye with anapparent visual magnitude of 5.00.[2]
This is anevolvedK-type star with astellar classification of K2 II-III,[4] which indicates aspectrum showing traits intermediate between thegiant andbright giant stages. It is most likely (98% chance) on thehorizontal branch, indicating that the star is generating energy through thethermonuclear fusion of helium at its core. With 4.32 times theSun's mass, it has expanded to around 48 times theradius of the Sun. Omega Hydrae is about 180[3] million years old and spinning with a leisurelyprojected rotational velocity of 2.3 km/s.[8] The star is radiating roughly 944[3] times thesolar luminosity from itsphotosphere at aneffective temperature of4,789 K.[7]
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