12 Ophiuchi

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12 Ophiuchi
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 16h 36m 21.44979s[1]
Declination –02° 19′ 28.5195″[1]
Apparent magnitude (V) 5.77[2]
Spectral type K1 V[3]
U−B color index +0.50
B−V color index +.82
Variable type BY Draconis
Radial velocity (Rv)–15.4 km/s
Proper motion (μ) RA: +456.04[1] mas/yr
Dec.: –309.63[1] mas/yr
Parallax (π)102.55 ± 0.40[1] mas
Distance31.8 ± 0.1 ly
(9.75 ± 0.04 pc)
Absolute magnitude (MV)5.57 ± 0.05[2]
Mass0.91[2] M
Radius0.84 ± 0.03[2] R
Diameter0.84 ± 0.03[2] D
Luminosity0.39 L
Luminosity (bolometric)0.45 L
Surface gravity (log g)4.59 ± 0.10[2] cgs
Temperature5,300[4] K
Metallicity102% Sun[4]
Metallicity [Fe/H]+0.04 ± 0.07[2] dex
Rotation21.3 days[5]
Rotational velocity (v sin i)2.4 ± 1.0[2] km/s
Age1.0–1.9[6] Gyr
Other designations
12 Oph, BD-01 3220, FK5 1433, GCTP 3773.00, GJ 631, HD 149661, HIP 81300, HR 6171, LHS 3224, LTT 6632, V2133 Oph, SAO 141269.
Database references

12 Ophiuchi is a variable star in the constellation Ophiuchus. No companions have yet been detected in orbit around this star, and it remains uncertain whether or not it possesses a dust ring.[7]

This star is categorized as a BY Draconis variable, with variable star designation V2133. The variability is attributed to large-scale magnetic activity on the chromosphere (in the form of starspots) combined with a rotational period that moved the active regions into (and out of) the line of sight. This results in low amplitude variability of 12 Ophiuchi's luminosity. The star also appears to display rapid variation in luminosity, possibly due to changes in the starspots.[8] Measurements of the long-term variability show two overlapping cycles of starspot activity (compared to the Sun's single, 11-year cycle.) The periods of these two cycles are 4.0 and 17.4 years.[9]

This star is among the top 100 target stars for NASA's planned Terrestrial Planet Finder mission [1]. However, the mission is now postponed indefinitely.

Its abundance of heavy elements (elements heavier than helium) is nearly identical to that of the Sun. The surface gravity is equal to '"`UNIQ--postMath-00000001-QINU`"', which is somewhat higher than the Sun's.[4] The space velocity is 30 km/s relative to the solar system. The high rotation period and active chromosphere are indicative of a relatively young star.[10][11]


  1. 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (November 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
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Fuhrmann, Klaus (February 2008), "Nearby stars of the Galactic disc and halo - IV", Monthly Notices of the Royal Astronomical Society 384 (1): 173–224, Bibcode 2008MNRAS.384..173F, doi:10.1111/j.1365-2966.2007.12671.x
  3. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey 5, Bibcode 1999MSS...C05....0H.
  4. 4.0 4.1 4.2 Flynn, C.; Morel, O. (1997), "Metallicities and kinematics of G and K dwarfs", Monthly Notices of the Royal Astronomical Society 286 (3): 617–625, arXiv:astro-ph/9609017, Bibcode 1997MNRAS.286..617F, doi:10.1093/mnras/286.3.617
  5. Soon, Willie; Frick, Peter; Baliunas, Sallie (1999), "Lifetime of Surface Features and Stellar Rotation: A Wavelet Time-Frequency Approach", The Astrophysical Journal 510 (2): L135–L138, arXiv:astro-ph/9811114, Bibcode 1999ApJ...510L.135S, doi:10.1086/311805
  6. Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal 687 (2): 1264–1293, arXiv:0807.1686, Bibcode 2008ApJ...687.1264M, doi:10.1086/591785
  7. H. J. Habing; P. Bouchet; C. Dominik; T. Encrenaz; A. Heske; M. Jourdain de Muizon et al. (1996). "First results from a photometric infrared survey for Vega-like disks around nearby main-sequence stars.". Astronomy and Astrophysics 315: L233–L236. Bibcode 1996A&A...315L.233H.
  8. J. D. Dorren; E. F. Guinan; E. F. (1982). "Evidence for starspots on single solar-like stars". Astronomical Journal 87: 1546–1557. Bibcode 1982AJ.....87.1546D. doi:10.1086/113245.
  9. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  10. H. J. Rocha-Pinto; B. V. Castilho; W. J. Maciel (2002). "Chromospherically young, kinematically old stars". Astronomy & Astrophysics 384 (3): 912–924. arXiv:astro-ph/0112452. Bibcode 2002A&A...384..912R. doi:10.1051/0004-6361:20011815. http://www.aanda.org/index.php?option=com_base_ora&url=articles/aa/full/2002/12/aa1635/aa1635.right.html&access=standard&Itemid=81.
  11. G. F. Porto de Mello; E. F. del Peloso; L. Ghezzi (2006). "Astrobiologically interesting stars within 10 parsecs of the Sun". Astrobiology 6 (2): 308–331. arXiv:astro-ph/0511180. Bibcode 2006AsBio...6..308P. doi:10.1089/ast.2006.6.308. PMID 16689649. http://www.liebertonline.com/doi/abs/10.1089/ast.2006.6.308.

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External links[edit]

  • Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).