Sigma Draconis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| Right ascension | 19h 32m 21.59021s |
| Declination | +69° 39′ 40.2358″ |
| Apparent magnitude (V) | 4.674 |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | K0 V |
| U−B color index | +0.386 |
| B−V color index | +0.791 |
| Variable type | None |
| Astrometry | |
| Radial velocity (Rv) | 26.55±0.13 km/s |
| Proper motion (μ) | RA: 597.384 mas/yr Dec.: −1738.286 mas/yr |
| Parallax (π) | 173.4939±0.0748 mas |
| Distance | 18.799 ± 0.008 ly (5.764 ± 0.002 pc) |
| Absolute magnitude (MV) | 5.89 |
| Details | |
| Mass | 0.84±0.02 M☉ |
| Radius | 0.772±0.009 R☉ |
| Luminosity | 0.42±0.04 L☉ |
| Surface gravity (log g) | 4.589±0.009 cgs |
| Temperature | 5,255±31 K |
| Metallicity [Fe/H] | −0.254 dex |
| Rotation | 27.7±0.77 days |
| Rotational velocity (v sin i) | 1.4 km/s |
| Age | 4.54±1.54 Gyr |
| Other designations | |
| Alsafi, σ Draconis, Sig Dra, σ Dra, 61 Draconis, BD+69°1053, GJ 764, HD 185144, HIP 96100, HR 7462, LHS 477 | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
Sigma Draconis is a single star in the northern constellation of Draco. It has the proper name Alsafi /ælˈseɪfi/, while Sigma Draconis, which is latinised from σ Draconis and abbreviated Sig Dra or σ Dra, is the Bayer designation. It has an apparent visual magnitude of 4.7, which is bright enough to be faintly visible to the naked eye. Based on parallax measurements, this star is located at a distance of 18.8 light years from the Sun. It is receding from the Sun with a radial velocity of 26.6 km/s.