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Alphard
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 09h 27m 35.2433s[1] |
| Declination | −08° 39′ 30.969″[1] |
| Apparent magnitude (V) | +2.00[2] |
| Characteristics | |
| Evolutionary stage | Giant star |
| Spectral type | K3IIIa[3] |
| U−B color index | +1.73[4] |
| B−V color index | +1.45[3] |
| Astrometry | |
| Radial velocity (Rv) | −4.3[5] km/s |
| Proper motion (μ) | RA: −14.49[1] mas/yr Dec.: 33.25[1] mas/yr |
| Parallax (π) | 18.40 ± 0.78 mas[1] |
| Distance | 177 ± 8 ly (54 ± 2 pc) |
| Absolute magnitude (MV) | −1.743±0.032[3] |
| Details | |
| Mass | 3.2±0.32[3] M☉ |
| Radius | 55.9±2.4[6] R☉ |
| Luminosity | 971+154 −133[3] L☉ |
| Luminosity (visual, LV) | 426[3][a] L☉ |
| Surface gravity (log g) | 1.77[6] cgs |
| Temperature | 4117±18[3] K |
| Metallicity [Fe/H] | −0.12[6] dex |
| Rotation | 2,991 days[7] |
| Rotational velocity (v sin i) | 1.1[7] km/s |
| Age | 420±160[8] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Alphard /ˈælfɑːrd/,[10] designated Alpha Hydrae (α Hydrae, abbreviated Alpha Hya, α Hya), is the brightest star in the constellation of Hydra. It is a single giant star, cooler than the Sun but larger and more luminous. It is about 177 light-years away.
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