36 Ophiuchi

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36 Ophiuchi A/B/C
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension A: 17h 15m 20.851s
B: 17h 15m 20.978s
C: 17h 16m 13.3624s[1]
Declination A: −26° 36′ 09.04″
B: −26° 36′ 10.18″
C: −26° 32′ 46.129″[1]
Apparent magnitude (V) 5.08/5.08/6.34[1]
Spectral type K2 V/K1 V/K5 V[1]
U−B color index 0.51(AB)/1.04
B−V color index 0.86(AB)/1.15
Variable type C: RS CV
Radial velocity (Rv) -0.6/0.0/-1.6[1] km/s
Proper motion (μ) RA: -488.2/-473/-480.06[1] mas/yr
Dec.: -1156.0/-1143/-1123.48[1] mas/yr
Parallax (π) 167.1 ± 1.1[1] mas
Distance 19.5 ± 0.1 ly
(5.98 ± 0.04 pc)
Companion 36 Ophiuchi B
Period (P) 568.9 yr
Semi-major axis (a) 14.7"
Eccentricity (e) 0.922
Inclination (i) 99.6°
Longitude of the node (Ω) -83.6°
Periastron epoch (T) 1763.39
36 Oph A/B
Mass 0.85/0.85 M
Radius 0.817 ± 0.016[2]/0.81 R
Luminosity (bolometric) 0.33/0.36[note 1] L
Luminosity (visual, LV) 0.28/0.27 L
Temperature 4,843 ± 134[2]/4,985 ± 20[3] K
Metallicity B: –0.31 ± 0.042[3] dex
Metallicity [Fe/H] A: –0.20[2] dex
Age 0.6-1.8[4][5] Gyr
36 Oph C
Mass 0.71 M
Radius 0.72 R
Luminosity (bolometric) 0.20[note 1] L
Luminosity (visual, LV) 0.09 L
Temperature 4,550 K
Metallicity 46-100% Sun
Other designations
36 Oph, GJ 663 AB and 664, HR 6402/6401/-, CD CD-26°12026, HD 155886/155885/156026, GCTP 3908.00 AB/3913.00, LHS 437/438/439, SAO 185198/185199/185213, HIP 84405/84478.
Database references
Exoplanet Archive data
Database references
Exoplanet Archive data
Database references
Exoplanet Archive data

36 Ophiuchi is a triple star system 19.5 light years away from Earth. It is in the constellation Ophiuchus.

The primary and secondary stars are nearly identical orange main sequence dwarves of spectral type K2/K1 and the tertiary star is an orange main sequence dwarf of spectral type K5.

Star C is separated from the A-B pair by 700 arc seconds, compared to a minimum of 4.6 arcsec for A-B, so it has a negligible effect on the movements of the A-B pair. Both A and B have active chromospheres.

Hunt for substellar objects[edit]

The McDonald Observatory team has set limits to the presence of one or more planets[4] around 36 Ophiuchi A with masses between 0.13 and 5.4 Jupiter masses and average separations spanning between 0.05 and 5.2 astronomical units, although beyond 1.5 AU orbits are inherently unstable around either 36 Ophiuchi A or 36 Ophiuchi B.[6]

See also[edit]


  1. ^ a b From L=4πR2σTeff4, where L is the luminosity, R is the radius, Teff is the effective surface temperature and σ is the Stefan–Boltzmann constant.


  1. ^ a b c d e f g h "SIMBAD Astronomical Database". Centre de Données astronomiques de Strasbourg. Retrieved 2013-08-23. 
  2. ^ a b c Demory, B.-O. et al. (October 2009), Mass-radius relation of low and very low-mass stars revisited with the VLTI, Astronomy and Astrophysics 505 (1): 205–215, arXiv:0906.0602, Bibcode:2009A&A...505..205D, doi:10.1051/0004-6361/200911976 
  3. ^ a b Taylor, B. J. (December 2005), Statistical Cataloging of Archival Data for Luminosity Class IV-V Stars. III. The Epoch 2004 [Fe/H] and Temperature Catalogs, The Astrophysical Journal Supplement Series 161 (2): 444–455, Bibcode:2005ApJS..161..444T, doi:10.1086/496885. Vizier catalog entry
  4. ^ a b Wittenmeyer et al. (2006).
  5. ^ 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 
  6. ^ Irwin et al. (1996).

Further reading[edit]

  • Irwin, Alan W.; Yang, Stephenson L. S. & Walker, Gordon A. H. (1996), 36 Ophiuchi AB: Incompatibility of the Orbit and Precise Radial Velocities, Publications of the Astronomical Society of the Pacific 108: 580, Bibcode:1996PASP..108..580I, doi:10.1086/133768 
  • Cayrel de Strobel, G.; Lebreton, Y.; Perrin, M.-N. & Cayrel, R. (1989), A thorough spectroscopic study of the very nearby triple system - 36 Ophiuchi, Astronomy and Astrophysics 225 (2): 369–380, Bibcode:1989A&A...225..369C 
  • Wittenmeyer, R. A.; Endl, Michael; Cochran, William D.; Hatzes, Artie P.; Walker, G. A. H.; Yang, S. L. S. & Paulson, Diane B. (2006), Detection Limits from the McDonald Observatory Planet Search Program, Astronomical Journal 132 (1): 177–188, arXiv:astro-ph/0604171, Bibcode:2006AJ....132..177W, doi:10.1086/504942 
  • Barnes, Sydney A. (2007), Ages for Illustrative Field Stars Using Gyrochronology: Viability, Limitations, and Errors, The Astrophysical Journal 669 (2): 1167–1189, arXiv:0704.3068, Bibcode:2007ApJ...669.1167B, doi:10.1086/519295 

External links[edit]