26 Draconis

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26 Draconis
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 17h 34m 59.59363s[1]
Declination +61° 52′ 28.4006″[1]
Apparent magnitude (V) 5.236[2]
Spectral type G0Va (F9V + K3V)[3]
U−B color index +0.100[2]
B−V color index +0.595[2]
Radial velocity (Rv) –12.7[4] km/s
Proper motion (μ) RA: 277.02[1] mas/yr
Dec.: –524.88[1] mas/yr
Parallax (π) 70.47 ± 0.37[1] mas
Distance 46.3 ± 0.2 ly
(14.19 ± 0.07 pc)
Primary 26 Dra A
Companion 26 Dra B
Period (P) 76.1 yr
Eccentricity (e) 0.18
Mass 1.30/0.83[6] M
Surface gravity (log g) 4.50[7] cgs
Temperature 6,000[7] K
Metallicity [Fe/H] -0.18[8] dex
Rotational velocity (v sin i) 10[9] km/s
Age 8.4–11.5[8] Gyr
Other designations
26 Dra, BD+61 1678, HD 160269, HIP 86036, HR 6573, LHS 3305, LTT 15223, SAO 17546.[10]

26 Draconis is a triple star system[11] in the constellation Draco, located 46 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.[3] A 1962 study estimated the masses of these two stars as 1.30 and 0.83 times the mass of the Sun, respectively.[6] 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.[8]

The third component, GJ 685, is a red dwarf spectral classification of M1V. As of 1970, this star is separated by 12.2 arc seconds with the AB pair and they share a common proper motion.[8] The space velocity components of 26 Draconis are U = +36.5, V = −4.3 and W = −21.8 km/s.[12] 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.[13] This system may be a member of the Ursa Major moving group.[14]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c Oja, T., "UBV photometry of stars whose positions are accurately known. III", Astronomy and Astrophysics Supplement Series 65 (2): 405–4. 
  3. ^ a b Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal 81: 245–249, Bibcode:1976AJ.....81..245E, doi:10.1086/111879 
  4. ^ Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode:1953QB901.W495..... 
  5. ^ Abt, Helmut A.; Willmarth, Daryl (2006). "The Secondaries of Solar-Type Primaries. I. The Radial Velocities". Astrophysical Journal Supplement 162 (1): 207–226. Bibcode:2006ApJS..162..207A. doi:10.1086/498095. 
  6. ^ a b Upgren, A. R. (October 1962). "Parallax and orbital motion of the triple system 26 Draconis from photographs taken with the Sproul 24-inch refractor". Astronomical Journal 67: 539–543. Bibcode:1962AJ.....67..539U. doi:10.1086/108760. 
  7. ^ a b Luck, R. Earle; Heiter, Ulrike (June 2006). "Dwarfs in the Local Region". The Astronomical Journal 131 (6): 3069–3092. Bibcode:2006AJ....131.3069L. doi:10.1086/504080. 
  8. ^ a b c d Makarov, V. V.; Zacharias, N.; Hennessy, G. S. (November 2008). "Common Proper Motion Companions to Nearby Stars: Ages and Evolution". The Astrophysical Journal 687 (1): 566–578. arXiv:0808.3414. Bibcode:2008ApJ...687..566M. doi:10.1086/591638. 
  9. ^ Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago 239 (1). Bibcode:1970CoAsi.239....1B. 
  10. ^ "HD 160269 -- Spectroscopic binary". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-02-17. 
  11. ^ Greaves, J. S.; Wyatt, M. C. (November 2003). "Some anomalies in the occurrence of debris discs around main-sequence A and G stars". Monthly Notices of the Royal Astronomical Society 345 (4): 1212–1222. Bibcode:2003MNRAS.345.1212G. doi:10.1046/j.1365-2966.2003.07037.x. 
  12. ^ Soderblom, David R.; Mayor, Michel (January 1993). "Stellar kinematic groups. I - The Ursa Major group". Astronomical Journal 105 (1): 226–249. Bibcode:1993AJ....105..226S. doi:10.1086/116422. 
  13. ^ Holmberg, J.; Nordström, B.; Andersen, J. (July 2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". Astronomy and Astrophysics 501 (3): 941–947. arXiv:0811.3982. Bibcode:2009A&A...501..941H. doi:10.1051/0004-6361/200811191. 
  14. ^ Greaves, J. S.; Wyatt, M. C.; Bryden, G. (August 2009). "Debris discs around nearby solar analogues". Monthly Notices of the Royal Astronomical Society 397 (2): 757–762(6). arXiv:0907.3677. Bibcode:2009MNRAS.397..757G. doi:10.1111/j.1365-2966.2009.15048.x.