Gamma Draconis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| Right ascension | 17h 56m 36.36988s |
| Declination | +51° 29′ 20.0242″ |
| Apparent magnitude (V) | 2.23 |
| Characteristics | |
| Spectral type | K5 III |
| U−B color index | +1.87 |
| B−V color index | +1.52 |
| Astrometry | |
| Radial velocity (Rv) | 28.19±0.36 km/s |
| Proper motion (μ) | RA: −8.48 mas/yr Dec.: −22.79 mas/yr |
| Parallax (π) | 21.14±0.10 mas |
| Distance | 154.3 ± 0.7 ly (47.3 ± 0.2 pc) |
| Absolute magnitude (MV) | −1.93 ± 0.07 |
| Details | |
| Mass | 2.14±0.16 M☉ |
| Radius | 51.8±0.26 R☉ |
| Luminosity | 598±21 L☉ |
| Surface gravity (log g) | 1.33±0.04 cgs |
| Temperature | 3,964±34 K |
| Metallicity [Fe/H] | +0.11±0.05 dex |
| Rotational velocity (v sin i) | 4.5±0.05 km/s |
| Age | 1.3±0.25 Gyr |
| Other designations | |
| Eltanin, 33 Draconis, BD+51°2282, FK5 676, HD 164058, HIP 87833, HR 6705, SAO 30653 | |
| Database references | |
| SIMBAD | data |
Gamma Draconis (γ Draconis, abbreviated Gamma Dra, γ Dra), formally named Eltanin /ɛlˈteɪnɪn/, is a star in the northern constellation of Draco. Contrary to its gamma-designation (historically third-ranked), it is the brightest object in Draco at magnitude 2.2, outshining Beta Draconis by nearly half a magnitude and Alpha Draconis by over a magnitude.
Gamma Draconis is at a distance of 154.3 light-years (47.3 parsecs) from the Sun, as determined by parallax measurements from the Hipparcos astrometry satellite. In 1728, while unsuccessfully attempting to measure the star's parallax, James Bradley discovered the aberration of light resulting from the relative movement of the Earth. Bradley's discovery confirmed Copernicus' theory that the Earth revolved around the Sun. It is drifting closer to the Solar System with a radial velocity of about –28 km/s.
In 1.5 million years, Gamma Draconis will pass within 28 light-years of Earth. For a period, if its current absolute magnitude does not change, it will be the brightest star in the night sky, nearly as bright as Sirius is at present. Nearby this red star to the south-southeast is Vega, a bright, well-known star in Lyra.