Upsilon Draconis

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Upsilon Draconis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 18h 54m 23.85632s[1]
Declination +71° 17′ 49.8906″[1]
Apparent magnitude (V) 4.827[2]
Spectral type K0 III[3]
U−B color index +1.10[4]
B−V color index +1.15[4]
Radial velocity (Rv) −11.1[2] km/s
Proper motion (μ) RA: +49.53[1] mas/yr
Dec.: +42.11[1] mas/yr
Parallax (π) 9.48 ± 0.45[1] mas
Distance 340 ± 20 ly
(105 ± 5 pc)
Absolute bolometric
Period (P) 258.48 d
Eccentricity (e) 0.21
Periastron epoch (T) 2441977.5 JD
Argument of periastron (ω)
Semi-amplitude (K1)
6.0 km/s
Mass 2.05[6] M
Radius 19[7] R
Luminosity 2.23[6] L
Surface gravity (log g) 2.53[2] cgs
Temperature 4,561±61[6] K
Metallicity [Fe/H] +0.01[2] dex
Age 1.37[6] Gyr
Other designations
υ Dra, 52 Dra, BD+71° 915, HD 176524, HIP 92782, HR 7180, SAO 9283[8]
Database references

Upsilon Draconis (υ Dra) is a binary star[5] system in the northern circumpolar constellation of Draco. It is faintly visible to the naked eye with an apparent visual magnitude of 4.83.[2] Based upon an annual parallax shift of 9.48 mas as measured from Earth, it is located around 340 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.02 due to interstellar dust.[9]

In Chinese, 紫微左垣 (Zǐ Wēi Zuǒ Yuán), meaning Left Wall of Purple Forbidden Enclosure, refers to an asterism consisting of υ Draconis, ι Draconis, η Draconis, ζ Draconis, θ Draconis, 73 Draconis, γ Cephei and 23 Cassiopeiae.[10] Consequently, ζ Draconis itself is known as 紫微左垣五 (Zǐ Wēi Zuǒ Yuán wu, English: the Fifth Star of Left Wall of Purple Forbidden Enclosure.),[11] representing 少弼 (Shǎobì), meaning The Second Minister.

This is a single-lined spectroscopic binary star system with an orbital period of 258.48 days and an eccentricity of 0.21.[5] The primary, component A, is an evolved K-type giant star with a stellar classification of K0 III.[3] It is a suspected barium star, which may indicate the orbiting companion, component B, is a white dwarf star.[12]

The measured angular diameter of the primary, after correction for limb darkening, is 1.69±0.02 mas.[13] At the estimated distance of Upsilon Draconis, this yields a physical size of about 19 times the Sun's radius.[7] It is about 1.37[6] billion years old with an estimated 2.05[6] times the mass of the Sun. The star is radiating 2.23[6] times the solar luminosity from its photosphere at an effective temperature of 4,561 K.[6]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e f Luck, R. Earle; Heiter, Ulrike (June 2007), "Giants in the Local Region", The Astronomical Journal, 133 (6): 2464−2486, Bibcode:2007AJ....133.2464L, doi:10.1086/513194. 
  3. ^ a b Eggen, O. J. (1962), "Space-velocity vectors for 3483 stars with proper motion and radial velocity", Royal Observatory Bulletin, 51, Bibcode:1962RGOB...51...79E. 
  4. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  5. ^ a b c Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727, Bibcode:2004A&A...424..727P, arXiv:astro-ph/0406573Freely accessible, doi:10.1051/0004-6361:20041213. 
  6. ^ a b c d e f g h Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal, 150 (3), 88, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88. 
  7. ^ 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:
  8. ^ "ups Dra -- Spectroscopic binary", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-05-30. 
  9. ^ Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430: 165–186, Bibcode:2005A&A...430..165F, arXiv:astro-ph/0409579Freely accessible, doi:10.1051/0004-6361:20041272. 
  10. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  11. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 10 日
  12. ^ Zacs, L.; et al. (April 1997), "An abundance analysis of the single-lined spectroscopic binaries with barium stars-like orbital elements. I. Analysis and results", A & A Supplement series, 122: 31−42, Bibcode:1997A&AS..122...31Z, doi:10.1051/aas:1997330. 
  13. ^ 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.