Gamma Hydri
γ Hydri, Latinised as Gamma Hydri, is a solitary, red-hued star in the constellation Hydrus. It has an apparent visual magnitude of 3.26, making it easily visible to the naked eye at night. Based upon an annual parallax shift of 15.24 mas as measured from Earth, the system is located about 214 light-years from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydrus |
| Right ascension | 03h 47m 14.34062s |
| Declination | −74° 14′ 20.2686″ |
| Apparent magnitude (V) | 3.26 |
| Characteristics | |
| Spectral type | M1 III |
| U−B color index | +1.98 |
| B−V color index | +1.62 |
| Astrometry | |
| Radial velocity (Rv) | +15.8±0.6 km/s |
| Proper motion (μ) | RA: +50.85 mas/yr Dec.: +114.74 mas/yr |
| Parallax (π) | 15.24 ± 0.11 mas |
| Distance | 214 ± 2 ly (65.6 ± 0.5 pc) |
| Absolute magnitude (MV) | −0.83 |
| Details | |
| Mass | 1.0 M☉ |
| Radius | 62±1 R☉ |
| Luminosity | 513 L☉ |
| Surface gravity (log g) | 0.84 cgs |
| Temperature | 3499 K |
| Metallicity [Fe/H] | 0.0 dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is an evolved red giant star with a stellar classification of M1 III, and is most likely on the asymptotic giant branch of the HR diagram. It is a semiregular variable that pulsates between magnitudes 3.26 and 3.33, although its period is not known precisely. It has about the same mass as the Sun, but has expanded to around 62 times the Sun's radius. The star is radiating 513 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,499 K.