36 Ophiuchi

36 Ophiuchi, formally named Guniibuu /ɡəˈniːbuː/, is a triple star system 19.5 light years from Earth. It is in the constellation Ophiuchus.

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]
Characteristics
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
Astrometry
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
Distance19.5 ± 0.1 ly
(5.98 ± 0.04 pc)
Orbit
Companion36 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
Details
36 Oph A/B
Mass0.85/0.85 M☉
Radius0.817 ± 0.016[2]/0.81 R☉
Luminosity (bolometric)0.33/0.36[note 1] L☉
Luminosity (visual, LV)0.28/0.27 L☉
Temperature4,843 ± 134[2]/4,985 ± 20[3] K
MetallicityB: –0.31 ± 0.042[3] dex
Metallicity [Fe/H]A: –0.20[2] dex
Age0.6-1.8[4][5] Gyr
36 Oph C
Mass0.71 M☉
Radius0.72 R☉
Luminosity (bolometric)0.20[note 1] L☉
Luminosity (visual, LV)0.09 L☉
Temperature4,550 K
Metallicity46-100% Sun
Other designations
36 Oph, Guniibuu (star A), 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, Gaia DR2 4109030160308320128 / 4109030160308317312 / 4109034455276324608.
Database references
SIMBADAB
A
B
C
Exoplanet ArchiveA
B
C
ARICNSA
B
C

The primary and secondary stars are nearly identical orange main sequence dwarfs of spectral type K2/K1; 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 its effect on the movements of the A-B pair is small. A and B have active chromospheres.

Nomenclature

In the Kamilaroi and Euahlayi Aboriginal peoples in modern-day New South Wales, Australia, the star A is called Guniibuu that represents the mythological robin red-breast bird. In 2016, the IAU organized a Working Group on Star Names (WGSN)[6] to catalog and standardize proper names for stars. The WGSN approved the name Guniibuu for the star A on 10 August 2018 and it is now so included in the List of IAU-approved Star Names.[7]

Hunt for substellar objects

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.[8]

The star C (or namely HD 156026) is among five nearby paradigms as K-type stars of a type in a 'sweet spot’ between Sun-analog stars and M stars for the likelihood of evolved life, per analysis of Giada Arney from NASA’s Goddard Space Flight Center.[9]

See also

Notes
  1. 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.

References
  1. "SIMBAD Astronomical Database". Centre de Données astronomiques de Strasbourg. Retrieved 2013-08-23.
  2. 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. 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. 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. "IAU Working Group on Star Names (WGSN)". Retrieved 17 September 2018.
  7. "IAU Catalog of Star Names". International Astronomical Union. Retrieved 2018-09-17.
  8. Irwin et al. (1996).
  9. Bill Steigerwald (2019-03-07). ""Goldilocks" Stars May Be "Just Right" for Finding Habitable Worlds". NASA. Retrieved 2020-05-12. 'I find that certain nearby K stars like 61 Cyg A/B, Epsilon Indi, Groombridge 1618, and HD 156026 may be particularly good targets for future biosignature searches,' said Arney.

Further reading
  • 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
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