26 Draconis
Star in the constellation Draco
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26 Draconis is a triple star system[14] in the constellation Draco, located 47 light-years from the Sun. Two of the system components, A and B, form a spectroscopic binary that completes an orbit every 76 years. The composite spectral classification of the AB pair is G0V, which decomposes to individual spectral types F9V and K3V.[5] A 1962 study estimated the masses of these two stars as 1.30 and 0.83 times the mass of the Sun, respectively.[8] The stars are considered moderately metal-poor compared to the Sun, which means they have a lower proportion of elements other than hydrogen or helium.[10]
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Draco |
| AB | |
| Right ascension | 17h 34m 59.62474s[1] |
| Declination | +61° 52′ 28.2418″[1] |
| Apparent magnitude (V) | 5.236[2] |
| C | |
| Right ascension | 17h 35m 34.47852s[3] |
| Declination | +61° 40′ 53.6281″[3] |
| Apparent magnitude (V) | 9.97[4] |
| Characteristics | |
| AB | |
| Evolutionary stage | main sequence[1] |
| Spectral type | G0Va (F9V + K3V)[5] |
| U−B color index | +0.100[2] |
| B−V color index | +0.595[2] |
| C | |
| Evolutionary stage | main sequence[3] |
| Spectral type | M0.5V[4] |
| B−V color index | +1.48[4] |
| Astrometry | |
| AB | |
| Radial velocity (Rv) | −15.72±0.33[1] km/s |
| Proper motion (μ) | RA: 236.247 mas/yr[1] Dec.: −466.111 mas/yr[1] |
| Parallax (π) | 69.2832±0.2004 mas[1] |
| Distance | 47.1 ± 0.1 ly (14.43 ± 0.04 pc) |
| Absolute magnitude (MV) | 4.58±0.011[6] |
| C | |
| Radial velocity (Rv) | −15.53±0.16[3] km/s |
| Proper motion (μ) | RA: 261.923 mas/yr[3] Dec.: −514.499 mas/yr[3] |
| Parallax (π) | 69.8921±0.0153 mas[3] |
| Distance | 46.67 ± 0.01 ly (14.308 ± 0.003 pc) |
| Orbit[7] | |
| Primary | 26 Dra A |
| Name | 26 Dra B |
| Period (P) | 76.1 yr |
| Semi-major axis (a) | 1.53″ |
| Eccentricity (e) | 0.18 |
| Inclination (i) | 104° |
| Longitude of the node (Ω) | 151° |
| Periastron epoch (T) | 1947 |
| Argument of periastron (ω) (secondary) | 307° |
| Details | |
| AB | |
| Mass | 1.30/0.83[8] M☉ |
| Surface gravity (log g) | 4.50[9] cgs |
| Temperature | 6,000[9] K |
| Metallicity [Fe/H] | −0.18[10] dex |
| Rotational velocity (v sin i) | 10[11] km/s |
| Age | 8.4–11.5[10] Gyr |
| C | |
| Mass | 0.55±0.06[4] M☉ |
| Radius | 0.54±0.05[4] R☉ |
| Surface gravity (log g) | 4.72±0.05[4] cgs |
| Temperature | 3816±69[4] K |
| Metallicity [Fe/H] | −0.15±0.09[4] dex |
| Rotation | 18.15+0.15 −0.16 d[4] |
| Rotational velocity (v sin i) | 1.33±0.42[4] km/s |
| Other designations | |
| ADS 10660, CCDM J17351+6152, WDS J17350+6153 | |
| AB: 26 Dra, BD+61 1678, GJ 684, HD 160269, HIP 86036, HR 6573, SAO 17546, LHS 3305, LTT 15223[12] | |
| C: GJ 685, HIP 86087, G 226-66, LHS 3306, LTT 15224[13] | |
| Database references | |
| SIMBAD | A |
| B | |
| C | |
The space velocity components of 26 Draconis are U = +36.5, V = −4.3 and W = −21.8 km/s.[15] This system is on an orbit through the Milky Way galaxy that has an eccentricity of 0.14, taking it as close as 23.1 kly (7.08 kpc) and as far as 30.4 kly (9.32 kpc) from the galactic core. The inclination of this orbit carries the star system as much as 0.75 kly (0.23 kpc) above the plane of the galactic disk.[16] This system may be a member of the Ursa Major moving group.[17]
Gliese 685
The third component, GJ 685, is a red dwarf with spectral classification of M0V. As of 1970, this star is separated by 737.9 arc seconds from the AB pair and they share a common proper motion.[18] The star GJ 685 has one known planet in orbit that was detected by radial velocity.[4]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination (°) |
Radius |
|---|---|---|---|---|---|---|
| b | ≥9.0+1.7 −1.8 M🜨 |
0.1344+0.0052 −0.0051 |
24.160+0.061 −0.047 |
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