26 Draconis Explained

26 Draconis is a triple star system^[1] 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. A 1962 study estimated the masses of these two stars as 1.30 and 0.83 times the mass of the Sun, respectively. 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.^[2]

Gliese 685

The third component, GJ 685, is a red dwarf 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. The Star GJ 685 has one known planet orbit that was detected by radial velocity. ^[3]

The space velocity components of 26 Draconis are U = +36.5, V = −4.3 and W = −21.8 km/s.^[4] This system is on an orbit through the Milky Way galaxy that has an eccentricity of 0.14, taking it as close as 23.1abbr=onNaNabbr=on and as far as 30.4abbr=onNaNabbr=on from the galactic core. The inclination of this orbit carries the star system as much as 0.75abbr=onNaNabbr=on above the plane of the galactic disk.^[5] This system may be a member of the Ursa Major moving group.^[6]

Notes and References

1. Greaves, J. S. . Wyatt, M. C. . November 2003 . Some anomalies in the occurrence of debris discs around main-sequence A and G stars . . 345 . 4 . 1212–1222 . 10.1046/j.1365-2966.2003.07037.x . 2003MNRAS.345.1212G . free.
2. Makarov . V. V. . Zacharias . N. . Hennessy . G. S. . Common Proper Motion Companions to Nearby Stars: Ages and Evolution . The Astrophysical Journal . 687 . 1 . 566–578 . November 2008 . 10.1086/591638 . 2008ApJ...687..566M . 0808.3414 . 17811620 .
3. 1903.11853. Makarov. V. V.. The HADES RV Programme with HARPS-N at TNG XI. GJ 685 b: A warm super-Earth around an active M dwarf. Zacharias. N.. Hennessy. G. S.. Astronomy & Astrophysics. 2019. A126. 625. 10.1051/0004-6361/201834969. 2019A&A...625A.126P. 85542910.
4. Soderblom, David R. . Mayor, Michel . January 1993 . Stellar kinematic groups. I - The Ursa Major group . Astronomical Journal . 105. 1 . 226–249 . 10.1086/116422 . 1993AJ....105..226S . free.
5. Holmberg, J. . Nordström, B. . Andersen, J. . The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics . Astronomy and Astrophysics . 501 . 3 . July 2009 . 941–947 . 10.1051/0004-6361/200811191 . 2009A&A...501..941H. 0811.3982 . 118577511 .
6. Greaves, J. S. . Wyatt, M. C. . Bryden, G. . Debris discs around nearby solar analogues . Monthly Notices of the Royal Astronomical Society . 397 . 2 . August 2009 . 757–762(6) . 10.1111/j.1365-2966.2009.15048.x . 2009MNRAS.397..757G. 0907.3677 . 17758971 .