Eta Draconis
 Location of η Draconis (circled) |
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| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Draco |
| Right ascension | 16h 23m 59.48594s |
| Declination | +61° 30′ 51.1699″ |
| Apparent magnitude (V) | +2.73 |
| Characteristics | |
| Spectral type | G8 III |
| U−B color index | +0.70 |
| B−V color index | +0.91 |
| Astrometry | |
| Radial velocity (Rv) | –14.3 km/s |
| Proper motion (μ) |
RA: –17.02 mas/yr Dec.: +56.95 mas/yr |
| Parallax (π) | 35.42 ± 0.09mas |
| Distance | 92.1 ± 0.2 ly (28.23 ± 0.07 pc) |
| Absolute magnitude (MV) | +0.58 |
| Details | |
| Mass | 2.55 M☉ |
| Radius | 11 R☉ |
| Luminosity | 60 L☉ |
| Surface gravity (log g) | 2.82 cgs |
| Temperature | 5,055 K |
| Metallicity [Fe/H] | –0.04 dex |
| Rotational velocity (v sin i) | 8 km/s |
| Age | 550 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta Draconis (η Dra, η Draconis) is a star in the northern circumpolar constellation of Draco. Despite having an apparent visual magnitude of only +2.73, it is the second brightest star in this generally faint constellation. Based upon parallax measurements collected during the Hipparcos mission, this star is located at a distance of about 92.1 light-years (28.2 parsecs) from Earth.
Eta Draconis is a large star with 2.55 times the mass of the Sun. The spectrum matches a stellar classification of G8 III, with the luminosity class III indicating this is an evolved giant star that has exhausted the supply of hydrogen at its core. It reached this stage in only 550 million years because higher mass stars such as this consume the supply of hydrogen more rapidly than the Sun. The measured angular diameter of this star, after correction for limb darkening, is 3.72 ± 0.07 mas. At the estimated distance of Eta Draconis, this yields a physical size of about 11 times the radius of the Sun. From its extended envelope, it is radiating around 60 times the luminosity of the Sun at an effective temperature of 5,055 K, giving it the yellow glow of a G-type star.
A nearby stellar companion is located at an angular separation of 5.1 arcseconds from Eta Draconis. This is an 8.8 magnitude K-type main sequence star with a stellar classification of K2 V. At the estimated distance of this star system, the two stars are separated by a physical distance of at least 140 AU and require at least a millennium to complete an orbit.
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