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Chi Draconis (χ Dra, χ Draconis, Chi Draconis) is a magnitude 3.6 binary star in the constellation Draco. It also has the Flamsteed designation 44 Draconis. At a distance of 27 light years, it is one of the forty or so closest stars.
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| Right ascension | 18h 21m 03.38255s[1] |
| Declination | +72° 43′ 58.2518″[1] |
| Apparent magnitude (V) | 3.570[2] |
| Characteristics | |
| Spectral type | F7V / K0V[3] |
| U−B color index | −0.06[4] |
| B−V color index | +0.49[4] |
| Variable type | Suspected[5] |
| Astrometry | |
| Radial velocity (Rv) | +32.4[2] km/s |
| Proper motion (μ) | RA: +531.21[1] mas/yr Dec.: −349.71[1] mas/yr |
| Parallax (π) | 120.05 ± 0.15 mas[3] |
| Distance | 27.17 ± 0.03 ly (8.33 ± 0.01 pc) |
| Absolute magnitude (MV) | 4.04[2] |
| Orbit[6] | |
| Primary | χ Dra Aa |
| Companion | χ Dra Ab |
| Period (P) | 0.7680599±0.000061 yr |
| Semi-major axis (a) | 0.1244±0.0011″ |
| Eccentricity (e) | 0.428±0.012 |
| Inclination (i) | 74.42±0.58° |
| Longitude of the node (Ω) | 230.30±0.51° |
| Periastron epoch (T) | 1,984.8324±0.0026 |
| Argument of periastron (ω) (secondary) | 119.3±1.1° |
| Details | |
| χ Dra Aa | |
| Mass | 1.029±0.026[3] M☉ |
| Radius | 1.20±0.09[3] R☉ |
| Luminosity | 1.86[3] L☉ |
| Temperature | 6,150±150[3] K |
| Metallicity [Fe/H] | −0.41[2] dex |
| Rotational velocity (v sin i) | 11[7] km/s |
| Age | 5.3[2] Gyr |
| χ Dra Ab | |
| Mass | 0.748±0.017[3] M☉ |
| Radius | 0.73±0.11[3] R☉ |
| Luminosity | 0.29[3] L☉ |
| Temperature | 4,940±200[3] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
χ Draconis is a spectroscopic binary which has been resolved using speckle interferometry.[4] The primary is an F7 main sequence star. The spectral type of the companion cannot be determined directly with any accuracy, but is known to be between G8 and K2 and is assumed to be K0. The properties of the secondary suggest that it is also a main-sequence star. The separation of the two stars varies between about 0.05″ and 0.2″ during the eccentric 182-day orbit.[9]
The primary star has a mass fractionally higher than the Sun's, but is significantly larger and hotter resulting in it being 86% more luminous.[3] Its age is estimated to be about five billion years.[2]
The secondary only has about three-quarters the mass of the Sun and is both cooler and smaller. It is only about 29% as luminous.[3] It is calculated to be 2.13 magnitudes fainter than the primary, so it would be of sixth magnitude if visible alone.[10]
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Multiple star catalogues list faint widely-separated visible companion stars: a 12th-magnitude star and a 14th-magnitude star about 3′ from χ Draconis, but only about 10″ from each-other.[11] Both have much smaller parallaxes than χ Draconis and are likely to be unrelated background objects.[12]
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