Upsilon Draconis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Draco |
| Right ascension | 18h 54m 23.85632s |
| Declination | +71° 17′ 49.8906″ |
| Apparent magnitude (V) | 4.827 |
| Characteristics | |
| Spectral type | K0 III |
| U−B color index | +1.10 |
| B−V color index | +1.15 |
| Astrometry | |
| Radial velocity (Rv) | −11.1 km/s |
| Proper motion (μ) |
RA: +49.53 mas/yr Dec.: +42.11 mas/yr |
| Parallax (π) | 9.48 ± 0.45mas |
| Distance | 340 ± 20 ly (105 ± 5 pc) |
| Absolute bolometric magnitude (Mbol) |
−0.70 |
| Orbit | |
| Period (P) | 258.48 d |
| Eccentricity (e) | 0.21 |
| Periastron epoch (T) | 2441977.5 JD |
|
Argument of periastron (ω) (secondary) |
298° |
|
Semi-amplitude (K1) (primary) |
6.0 km/s |
| Details | |
| Mass | 2.05 M☉ |
| Radius | 19 R☉ |
| Luminosity | 2.23 L☉ |
| Surface gravity (log g) | 2.53 cgs |
| Temperature | 4,561±61 K |
| Metallicity [Fe/H] | +0.01 dex |
| Age | 1.37 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Upsilon Draconis (υ Dra) is a binary star system in the northern circumpolar constellation of Draco. It is faintly visible to the naked eye with an apparent visual magnitude of 4.83. Based upon an annual parallax shift of 9.48 mas as measured from Earth, it is located around 340 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.02 due to interstellar dust.
In Chinese, 紫微左垣 (Zǐ Wēi Zuǒ Yuán), meaning Left Wall of Purple Forbidden Enclosure, refers to an asterism consisting of υ Draconis, ι Draconis, η Draconis, ζ Draconis, θ Draconis, 73 Draconis, γ Cephei and 23 Cassiopeiae. Consequently, ζ Draconis itself is known as 紫微左垣五 (Zǐ Wēi Zuǒ Yuán wu, English: the Fifth Star of Left Wall of Purple Forbidden Enclosure.), representing 少弼 (Shǎobì), meaning The Second Minister.
This is a single-lined spectroscopic binary star system with an orbital period of 258.48 days and an eccentricity of 0.21. The primary, component A, is an evolved K-type giant star with a stellar classification of K0 III. It is a suspected barium star, which may indicate the orbiting companion, component B, is a white dwarf star.
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