Gamma Draconis
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
Draco |
| Right ascension | 17h 56m 36.4s |
| Declination | +51° 29′ 20.3″ |
| Apparent magnitude (V) | 2.24 |
| Characteristics | |
| Spectral type | K5 III |
| U-B color index | 1.87 |
| B-V color index | 1.52 |
| Variable type | ? |
| Astrometry | |
| Radial velocity (Rv) | -28 km/s |
| Proper motion (μ) | RA: -8.52 mas/yr Dec.: -23.05 mas/yr |
| Parallax (π) | 22.10 ± 0.46 mas |
| Distance | 148 ± 3 ly (45.2 ± 0.9 pc) |
| Absolute magnitude (MV) | -1.04 |
| Details | |
| Mass | 1.7 M☉ |
| Radius | 50 R☉ |
| Luminosity | 600 L☉ |
| Temperature | 4,000 K |
| Metallicity | ? |
| Rotation | <17 km/s. |
| Age | ? years |
| Other designations | |
Gamma Draconis (γ Dra / γ Draconis) is a star in the constellation Draco. It has the traditional name Eltanin (also Etamin).
Eltanin is an orange giant of spectral type K5, lying 148 light years away. Despite its Bayer designation of "gamma," it is actually the brightest star in Draco, outshining Rastaban (Beta Draconis) by nearly half a magnitude. In fact, the name "Rastaban" was formerly used for Eltanin, and the two terms share an Arabic root meaning "serpent" or "dragon." Its proximity to the point directly overhead of London has also earned it the name "Zenith Star."
In 1.5 million years, Eltanin will pass within 28 light years of Earth. At this point it will be the brightest star in the night sky, surpassing Sirius.
In 1728, while unsuccessfully attempting to measure the parallax of this star, James Bradley discovered the aberration of light resulting from the movement of the Earth. Bradley's discovery proved Copernicus' theory that the Earth revolved around the Sun.
[edit] See also
[edit] References
Kaler, Jim (2004). "STARS: Eltanin". Retrieved July 11, 2005.
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