Observation data Epoch J2000 Equinox J2000 | |
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Constellation | Hydra |
Right ascension | 14h23m 05.77393s[1] |
Declination | −27° 45′ 14.4609″[1] |
Apparent magnitude (V) | 4.78[2] |
Characteristics | |
Evolutionary stage | giant |
Spectral type | K4 III[3] |
B−V color index | 1.300±0.040[2] |
Astrometry | |
Radial velocity (Rv) | 19.7±0.9[2] km/s |
Proper motion (μ) | RA: −202.476[1] mas/yr Dec.: −117.186[1] mas/yr |
Parallax (π) | 19.2042 ± 0.2252 mas[1] |
Distance | 170 ± 2 ly (52.1 ± 0.6 pc) |
Absolute magnitude (MV) | 1.36[2] |
Details | |
Mass | 1.31[4] M☉ |
Radius | 13.47+0.48 −1.26[1] R☉ |
Luminosity | 54.9+0.8 −1.5[1] L☉ |
Surface gravity (log g) | 2.25[5] cgs |
Temperature | 4,255±31[4] K |
Metallicity [Fe/H] | 0.08[5] dex |
Other designations | |
k Hya, 51 Hya, NSV 6648, CD−27°9803, HD 125932, HIP 70306, HR 5381, SAO 182483[6] | |
Database references | |
SIMBAD | data |
51 Hydrae is a single[7] star in the equatorial constellationofHydra,[6] located 170 light years away from the Sun.[1] It has the Bayer designation k Hydrae; 51 Hydrae is the Flamsteed designation.[6] This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.78. It is moving further from the Earth with a heliocentric radial velocity of +20 km/s.[2] Eggen (1971) listed it as a member of the η Cephei group of old-disk stars.[8]
This is an evolved giant star with a stellar classification of K4 III,[3] which indicates it has exhausted the supply of hydrogen at its core and expanded off the main sequence. It has 1.31[4] times the mass of the Sun but has swollen to 13.5[1] times the Sun's radius. The star is radiating 55[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,255 K.[4]
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