Alpha Serpentis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Serpens |
| Right ascension | 15h 44m 16.07431s |
| Declination | +06° 25′ 32.2633″ |
| Apparent magnitude (V) | 2.623 |
| Characteristics | |
| Evolutionary stage | Horizontal branch |
| Spectral type | K2 IIIb CN1 |
| U−B color index | +1.248 |
| B−V color index | +1.167 |
| Astrometry | |
| Radial velocity (Rv) | +2.63 km/s |
| Proper motion (μ) | RA: +133.84 mas/yr Dec.: +44.81 mas/yr |
| Parallax (π) | 44.10±0.19 mas |
| Distance | 74.0 ± 0.3 ly (22.68 ± 0.10 pc) |
| Absolute magnitude (MV) | +0.88±0.03 |
| Details | |
| Mass | 1.61±0.18 M☉ |
| Radius | 12.19 R☉ |
| Luminosity | 58.9±3 L☉ |
| Surface gravity (log g) | 2.4 cgs |
| Temperature | 4,687±59 K |
| Metallicity [Fe/H] | 0.189 dex |
| Rotational velocity (v sin i) | 4.3 km/s |
| Age | 2.06±0.33 Gyr |
| Other designations | |
| Unukalhai, Cor Serpentis, Alpha Ser, α Ser, 24 Serpentis, BD+06°3088, HD 140573, HIP 77070, HR 5854, SAO 121157, ADS 9765, CCDM 15442+0626 | |
| Database references | |
| SIMBAD | data |
Alpha Serpentis or α Serpentis, formally named Unukalhai (/ˌjuːnək.ælˈheɪ/), is a star in the head (Serpens Caput) of the equatorial constellation of Serpens. With an apparent visual magnitude of 2.6, this star is the brightest in the constellation and it can be viewed with the naked eye from most of the Earth. Parallax measurements yield an estimated distance of about 74 light-years (23 parsecs) from the Sun.