Omega Draconis
Star in the constellation Draco
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Omega Draconis, Latinized from ω Draconis and also known as 28 Draconis, is a binary star in the constellation of Draco. The system is fairly close, and is located about 78 light-years (24 parsecs) away, based on its parallax.[1]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Draco |
| Right ascension | 17h 36m 57.09431s[1] |
| Declination | +68° 45′ 28.6815″[1] |
| Apparent magnitude (V) | 4.80[2] |
| Characteristics | |
| Evolutionary stage | main sequence[1] |
| Spectral type | F5V[3] |
| U−B color index | −0.01[2] |
| B−V color index | +0.43[2] |
| Astrometry | |
| Radial velocity (Rv) | −13.98±0.02[4] km/s |
| Proper motion (μ) | RA: +1.690[1] mas/yr Dec.: +321.452[1] mas/yr |
| Parallax (π) | 42.0939±0.1425 mas[1] |
| Distance | 77.5 ± 0.3 ly (23.76 ± 0.08 pc) |
| Absolute magnitude (MV) | 2.95[5] |
| Orbit[6] | |
| Period (P) | 5.2797766±0.0000044 d |
| Semi-major axis (a) | 3.469±0.017 mas |
| Eccentricity (e) | 0.00220±0.00031 |
| Inclination (i) | 151.4±1.1° |
| Longitude of the node (Ω) | 1.23±0.32° |
| Periastron epoch (T) | JD 2454349.083±0.083 |
| Argument of periastron (ω) (secondary) | 314.8±5.6° |
| Semi-amplitude (K1) (primary) | 36.254±0.016 km/s |
| Semi-amplitude (K2) (secondary) | 44.720±0.016 km/s |
| Details | |
| ω Dra A | |
| Mass | 1.46±0.16 M☉ |
| Luminosity | 5.61[5] L☉ |
| Temperature | 6,500 K |
| Metallicity [Fe/H] | 0.18±0.05[5] dex |
| Age | 1.9[5] Gyr |
| ω Dra B | |
| Mass | 1.18±0.13 M☉ |
| Temperature | 5,900 K |
| Metallicity [Fe/H] | 0.0 dex |
| Other designations | |
| ω Dra, 28 Dra, BD+68°949, GJ 4017, HD 160922, HIP 86201, HR 6596, SAO 17576 | |
| Database references | |
| SIMBAD | data |
Omega Draconis is a spectroscopic binary, which means the two stellar components are too close to be resolved but periodic Doppler shifts in their spectra indicate orbital motion. In this case, light from both stars can be detected, and it is a double-lined spectroscopic binary. The orbital period of the system is 5.28 days, and the eccentricity of the system is 0.00220, implying a nearly circular orbit. The primary has a mass of 1.46 M☉, and is an F-type main-sequence star. The secondary is less massive, at 1.18 M☉.[6]
Nomenclature
With 27 Draconis, it composed the Arabs' الأظفار الذئب al-ʼaẓfār al-dhiʼb, "the hyena's claws" in the asterism of the Mother Camels.[7] The two stars have been distinguished as Adfar Aldib I (ω) and Adfar Aldib II (27 Draconis).[8]
In Chinese, 尚書 (Shàng Shū), meaning Royal Secretary, refers to an asterism consisting of ω Draconis, 15 Draconis, 18 Draconis and 19 Draconis.[9] Consequently, ω Draconis itself is known as 尚書一 (Shàng Shū yī, English: the First Star of Royal Secretary.).[10]