8 Draconis

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8 Draconis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension  12h 55m 28.550015s[1]
Declination +65° 26′ 18.5079″[1]
Apparent magnitude (V) 5.225[2]
Spectral type F1VmA7(n)[3]
B−V color index 0.303±0.005[4]
Variable type Gamma Doradus[5]
Radial velocity (Rv)+9.0[6] km/s
Proper motion (μ) RA: −4.235[1] mas/yr
Dec.: −30.174[1] mas/yr
Parallax (π)34.0276 ± 0.0922[1] mas
Distance95.9 ± 0.3 ly
(29.39 ± 0.08 pc)
Absolute magnitude (MV)2.90[4]
Mass1.56[7] M
Radius1.50[7] R
Luminosity5.75[4] L
Surface gravity (log g)4.01[3] cgs
Temperature7,129[3] K
Metallicity [Fe/H]−0.14[3] dex
Rotational velocity (v sin i)119.6[8] km/s
Age250±200[7] Myr
Other designations
Taiyi, 8 Dra, IR Draconis, BD+66°778, FK5 486, HD 112429, HIP 63076, HR 4916, SAO 15941[9]
Database references

8 Draconis, formally named Taiyi /ˌtˈj/,[10] is a single[11] star in the northern circumpolar constellation of Draco. Based upon an annual parallax shift of 34.14 mas as seen from the Earth,[12] the star is located approximately 96 light-years from the Sun. It is moving further away with a heliocentric radial velocity of +9 km/s,[6] having come within 40.6 ly some 2.6 million years ago.[4]

This is an F-type main-sequence star with a stellar classification of F1VmA7(n),[3] it is a Gamma Doradus variable star with a brightness variation of about one tenth of a magnitude.[5] 8 Dra has a relatively high rate of rotation, showing a projected rotational velocity of 120 km/s.[8] The star has 1.56 times the mass of the Sun and 1.50 times the Sun's radius.[7] It is radiating 5.75[4] times the Sun's luminosity from its photosphere at an effective temperature of 7,129 K.[3] An infrared excess has been detected at wavelengths of 24 and 70μm, which suggests the presence of a circumstellar disk orbiting the star.[7]


8 Draconis is the star's Flamsteed designation. It also received the variable star designation IR Draconis in 2000, after its variability had been discovered using Hipparcos photometry.[5]

The star bore the traditional Chinese name of Taiyi,[13] from 太乙 (Tài Yǐ) or 太一 (Tài Yī, the Great One), both of which refer to Tao. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[14] to catalogue and standardize proper names for stars; the WGSN approved the name Taiyi for this star on 30 June 2017 and it is now so entered on the List of IAU-approved Star Names.[10]


  1. ^ a b c d e 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. ^ Høg, E; Fabricius, C; Makarov, V. V; Urban, S; Corbin, T; Wycoff, G; Bastian, U; Schwekendiek, P; Wicenec, A (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
  3. ^ a b c d e f Gray, R. O; Corbally, C. J; Garrison, R. F; McFadden, M. T; Robinson, P. E (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.
  4. ^ a b c d e 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.
  5. ^ a b c Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  6. ^ a b Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
  7. ^ a b c d e Plavchan, Peter; et al. (2009), "New Debris Disks Around Young, Low-Mass Stars Discovered with the Spitzer Space Telescope", The Astrophysical Journal, 698 (2): 1068–94, arXiv:0904.0819, Bibcode:2009ApJ...698.1068P, doi:10.1088/0004-637X/698/2/1068.
  8. ^ a b Schröder, C.; et al. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377.
  9. ^ "8 Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-23.
  10. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  11. ^ 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  12. ^ Van Leeuwen, F (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  13. ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 7. Retrieved 2018-07-14.
  14. ^ "International Astronomical Union | IAU". www.iau.org. Retrieved 2018-01-16.