HD 212771
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 27m 03.072s |
| Declination | −17° 15′ 49.16″ |
| Apparent magnitude (V) | 7.6±0.01 |
| Characteristics | |
| Evolutionary stage | red giant branch |
| Spectral type | G8 IV |
| U−B color index | +0.54 |
| B−V color index | +0.88 |
| Astrometry | |
| Radial velocity (Rv) | 14.9±0.03 km/s |
| Proper motion (μ) | RA: −85.892 mas/yr Dec.: −104.042 mas/yr |
| Parallax (π) | 8.9648±0.0314 mas |
| Distance | 364 ± 1 ly (111.5 ± 0.4 pc) |
| Absolute magnitude (MV) | 2.04 |
| Details | |
| Mass | 1.42±0.07 M☉ |
| Radius | 4.44±0.13 R☉ |
| Luminosity | 11.67±0.57 L☉ |
| Surface gravity (log g) | 3.263±0.010 cgs |
| Temperature | 5,065±75 K |
| Metallicity [Fe/H] | −0.09±0.01 dex |
| Age | 2.90±0.47 Gyr |
| Other designations | |
| BD−17°6526, HD 212771, HIP 110813, SAO 165086 | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HD 212771, also named Lionrock, is a solitary star in the equatorial-southern zodiac constellation of Aquarius. It has an apparent magnitude of 7.60, making it readily visible with binoculars but not the naked eye. Parallax measurements place the object at a distance of 364 light-years, and is currently receding with a radial velocity of 15 km/s.
HD 212771 has a stellar classification of G8 IV, indicating that it is a subgiant evolving towards the red giant branch after being an F-type main-sequence star for 1.7 billion years. However, a close analysis of its asteroseismology and properties indicate that it has already reached the red giant branch. It has 142% the mass of the Sun and 4.4 times its radius. It radiates at 11.67 solar luminosities from its slightly enlarged photosphere at an effective temperature of 5,065 K, giving it a yellow-hue. Unlike most planetary hosts, HD 212771 is slightly metal deficient, and spins with a projected rotational velocity of about 2 km/s.