Upsilon1 Hydrae
Upsilon1 Hydrae (υ1 Hydrae, abbreviated Ups1 Hya, υ1 Hya), also named Zhang, is a yellow-hued star in the constellation of Hydra. It is visible to the naked eye, having an apparent visual magnitude of 4.12. Based upon an annual parallax shift of 12.36 mas as seen from Earth, it is located about 264 light-years from the Sun. The star is moving closer to the Sun with a radial velocity of −14.34 km/s. In 2005 it was announced that it had a substellar companion.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 09h 51m 28.69384s |
| Declination | −14° 50′ 47.7710″ |
| Apparent magnitude (V) | 4.12 |
| Characteristics | |
| Spectral type | G6/8III |
| U−B color index | +0.65 |
| B−V color index | +0.92 |
| Astrometry | |
| Radial velocity (Rv) | −14.34 km/s |
| Proper motion (μ) | RA: +18.88 mas/yr Dec.: −21.85 mas/yr |
| Parallax (π) | 12.36 ± 0.26 mas |
| Distance | 264 ± 6 ly (81 ± 2 pc) |
| Absolute magnitude (MV) | −0.43 |
| Details | |
| Mass | 3.33 M☉ |
| Radius | 14.69 R☉ |
| Luminosity | 162 L☉ |
| Surface gravity (log g) | 2.95 cgs |
| Temperature | 5,185 K |
| Metallicity [Fe/H] | 0.10 dex |
| Rotational velocity (v sin i) | 2.11 km/s |
| Age | 270 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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