7 Draconis

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7 Draconis
Observation data
Epoch J2000.0      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 /tiˈɛnj/ (or) /ˌtjɛnˈj/,[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[edit]

7 Draconis is the star's Flamsteed designation.

The star bore the traditional Chinese name of Tianyi,[9] from 天乙 (Tiān Yǐ) or 天一 (Tiān Yī, the Celestial Great One), a deity in Taoism. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[10] 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 on the List of IAU-approved Star Names.[6]

References[edit]

  1. ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. ^ a b c d e f g h 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.
  3. ^ a b "6 Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-23.
  4. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  5. ^ a b McDonald, I.; et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society, 427: 343, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  6. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  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, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
  9. ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 7. Retrieved 2018-07-14.
  10. ^ "International Astronomical Union | IAU". www.iau.org. Retrieved 2018-01-16.