Astronomy:7 Draconis

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Short description: Star in the constellation Draco
7 Draconis
Observation data
Equinox J2000.0]] (ICRS)
Constellation Draco
Right ascension  12h 47m 34.34473s[1]
Declination +66° 47′ 25.0977″[1]
Apparent magnitude (V) 5.43[2]
Characteristics
Spectral type K5 III[2]
B−V color index 1.567±0.006[2]
Astrometry
Radial velocity (Rv)+11.33[3] km/s
Proper motion (μ) RA: 6.674[1] mas/yr
Dec.: −6.498[1] mas/yr
Parallax (π)4.1601 ± 0.1056[1] mas
Distance780 ± 20 ly
(240 ± 6 pc)
Absolute magnitude (MV)−1.35[2]
Details
Radius67[4] R☉
Luminosity1,024.45[2] L☉
Temperature3,945[5] K
Other designations
Tianyi, 7 Dra, BD+67°764, FK5 3020, HD 111335, HIP 62423, HR 4863, SAO 15902[3]
Database references
SIMBADdata

7 Draconis, also named Tianyi /tiænˈjiː/,[6] is a single[7] star in the northern circumpolar constellation of Draco. It is visible to the naked eye as a faint orange-hued star with a stellar classification of 5.43.[2] Based upon an annual parallax shift of 4.16 mas as seen from the Earth,[1] the star is located approximately 780 light-years from the Sun.

This is an evolved giant star with a stellar classification of K5 III.[2] The measured angular diameter of this star, after correction for limb darkening, is 2.61±0.03 mas.[8] At its estimated distance, this yields a physical size of about 67 times the radius of the Sun.[4] It is radiating about 1,024[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,945 K.[5]

Nomenclature

7 Draconis is the star's Flamsteed designation.

The star bore the traditional Chinese name of Tianyi,[9][10] from 天乙 (Tiān Yǐ) or 天一 (Tiān Yī, the Celestial Great One), a deity in Taoism. Alternatively, Tianyi may refer to 10 Draconis[12] or κ Draconis,[13] with 7 and 8 Draconis forming Neichu, representing a private kitchen.[14] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalogue and standardize proper names for stars. The WGSN approved the name Tianyi for this star on 30 June 2017 and it is now so entered in the IAU Catalog of Star Names.[16]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  3. ↑ 3.0 3.1 "6 Dra". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=6+Dra. 
  4. ↑ 4.0 4.1 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1, https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41.  The radius (R*) is given by:
    2⋅R*=(240⋅2.61⋅10−3) AU0.0046491 AU/R⨀≈134.7⋅R⨀
  5. ↑ 5.0 5.1 McDonald, I. et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–357, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M. 
  6. ↑ "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. 
  7. ↑ Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  8. ↑ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431 (2): 773–777, doi:10.1051/0004-6361:20042039, Bibcode: 2005A&A...431..773R. 
  9. ↑ Bonnet-Bidaud, Jean-Marc; Praderie, Françoise; Whitfield, Susan (March 2009). "The Dunhuang Chinese sky: A comprehensive study of the oldest known star atlas". Journal of Astronomical History and Heritage 12 (1): 39–59. doi:10.3724/SP.J.1440-2807.2009.01.04. Bibcode: 2009JAHH...12...39B. 
  10. ↑ "WG Triennial Report (2015-2018) - Star Names". p. 7. https://exopla.net/wp-content/uploads/2025/04/2018_WGSN-triennial-report-2015-2018.pdf. 
  11. ↑ Yi, Shitong (April 1981). 科学出版社. 
  12. ↑ Stellarium, citing Yi Shitong, 1981[11]
  13. ↑ Yang, Bo-Shun; Hoffmann, Susanne M. (December 2024). "Identification of Z Cam's Historical Counterpart: The Quest for an Ancient Nova". Research in Astronomy and Astrophysics 24 (12): 125004. doi:10.1088/1674-4527/ad89aa. Bibcode: 2024RAA....24l5004Y. 
  14. ↑ Ridpath, Ian. "Star Tales - Draco". http://ianridpath.com/startales/draco.html. 
  15. ↑ "International Astronomical Union | IAU". https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  16. ↑ "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/. 




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