78 Ursae Majoris is a binary star system in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of 4.93.[1] Parallax estimates by Hipparcos put it at a distance of 83 light-years (25 pc),[2] but it is drifting closer with a radial velocity of −5 km/s.[3] The system is a candidate member of the Ursa Major Moving Group.[4]

The binary nature of this system was announced by S. W. Burnham in 1894.[5] The pair orbit each other with a period of 105 years and an eccentricity of 0.39. Their semimajor axis has an angular size of 1.2 arcsecond and the orbital plane is inclined by 47°.[6]

The primary member, designated component A, has a magnitude of 5.02[7] and is an F-type main-sequence star with a stellar classification of F2V.[8] It is 785[9] million years old and is spinning with a projected rotational velocity of 92 km/s.[10] The star has 1.34[9] times the mass of the Sun and is radiating 5.75[3] times the Sun's luminosity from its photosphere at an effective temperature of 6,908 K.[9]

The secondary, designated component B, has a visual magnitude of 7.88.[7] It is a G-type main-sequence star with a class of G6V.[11] The star is a suspected variable.[12]

References

  1. ^ "* 78 UMa". Retrieved 19 August 2017.
  2. ^ 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. S2CID 18759600
  3. ^ Anderson, E. & Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters. 38 (5): 331, arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644
  4. ^ Nakajima, Tadashi & Morino, Jun-Ichi (2012), "Potential Members of Stellar Kinematic Groups within 30 pc of the Sun", The Astronomical Journal. 143 (1): 2, Bibcode:2012AJ....143....2N. doi:10.1088/0004-6256/143/1/2
  5. ^ "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 19 August 2017.
  6. ^ Drummond, Jack D. (March 2014), "Binary Stars Observed with Adaptive Optics at the Starfire Optical Range", The Astronomical Journal. 147 (3): 10, Bibcode:2014AJ....147...65D. doi:10.1088/0004-6256/147/3/65. 65
  7. ^ Fabricius, C. et al. (2002). "The Tycho double star catalogue". Astronomy and Astrophysics. 384: 180–189. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822
  8. ^ Gray, R. O. et al. (2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". The Astronomical Journal. 126 (4): 2048. arXiv:astro-ph/0308182. Bibcode:2003AJ....126.2048G. doi:10.1086/378365. S2CID 119417105
  9. ^ David, Trevor J. & Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal. 804 (2): 146, arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. S2CID 33401607
  10. ^ Ammler-von Eiff, Matthias & Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics. 542: A116, arXiv:1204.2459. Bibcode:2012A&A...542A.116A. doi:10.1051/0004-6361/201118724. S2CID 53666672
  11. ^ Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal. 81: 245–249, Bibcode:1976AJ.....81..245E. doi:10.1086/111879
  12. ^ Baize, P. & Petit, M. (March 1989), "Etoiles doubles orbitales à composantes variables", Astronomy and Astrophysics, Supplemental Series. 77: 497–511, Bibcode:1989A&AS...77..497B