Beta Hydri
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydrus |
| Right ascension | 00h 25m 45.07036s |
| Declination | −77° 15′ 15.2860″ |
| Apparent magnitude (V) | 2.80 |
| Characteristics | |
| Spectral type | G2 IV |
| U−B color index | +0.11 |
| B−V color index | +0.62 |
| Astrometry | |
| Radial velocity (Rv) | +22.4 km/s |
| Proper motion (μ) | RA: +2,219.54 mas/yr Dec.: +324.09 mas/yr |
| Parallax (π) | 134.07±0.11 mas |
| Distance | 24.33 ± 0.02 ly (7.459 ± 0.006 pc) |
| Absolute magnitude (MV) | 3.45 ± 0.01 |
| Details | |
| Mass | 1.107±0.009 M☉ |
| Radius | 1.831±0.009 R☉ |
| Luminosity | 3.45±0.10 L☉ |
| Surface gravity (log g) | 3.97±0.04 cgs |
| Temperature | 5,917±25 K |
| Metallicity [Fe/H] | −0.12±0.02 dex |
| Rotation | 23.0±0.8 days |
| Rotational velocity (v sin i) | 6.0 km/s |
| Age | 6.1—7.5 Gyr |
| Other designations | |
| β Hyi, CD−77 15, CPD−77 16, FK5 11, GJ 19, HD 2151, HIP 2021, HR 98, SAO 255670, LFT 43, LHS 6, LPM 22, LTT 226, PLX 69 | |
| Database references | |
| SIMBAD | data |
Beta Hydri (β Hyi, β Hydri) is a star in the southern circumpolar constellation of Hydrus. (Note that Hydrus is not the same as Hydra.) With an apparent visual magnitude of 2.8, this is the brightest star in the constellation. Based upon parallax measurements the distance to this star is about 24.33 light-years (7.46 parsecs).
At a distance of 13°, it is the closest easily visible star to the south celestial pole, and around 150 BC it was within two degrees of it, which made it the southern pole star.