36 Ophiuchi (or Guniibuu for component A) is a triple star system 19.5 light-years from Earth. It is in the constellation Ophiuchus.
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| 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[2] |
| Declination | A: −26° 36′ 09.04″ B: −26° 36′ 10.18″ C: −26° 32′ 46.129″[2] |
| Apparent magnitude (V) | 5.08/5.03/6.34[2] |
| Characteristics | |
| Spectral type | K2 V/K1 V/K5 V[2] |
| U−B color index | 0.51(AB)/1.04 |
| B−V color index | 0.85(AB)/1.16 |
| Variable type | C: RS CVn |
| Astrometry | |
| 36 Oph A | |
| Radial velocity (Rv) | −0.6[2] km/s |
| Proper motion (μ) | RA: −498.600±0.123[3] mas/yr Dec.: −1149.158±0.086[3] mas/yr |
| Parallax (π) | 168.0031 ± 0.1343 mas[3] |
| Distance | 19.41 ± 0.02 ly (5.952 ± 0.005 pc) |
| 36 Oph B | |
| Radial velocity (Rv) | 0.0[2] km/s |
| Proper motion (μ) | RA: −465.861±0.111[4] mas/yr Dec.: −1141.168±0.073[4] mas/yr |
| Parallax (π) | 168.1303 ± 0.1081 mas[4] |
| Distance | 19.40 ± 0.01 ly (5.948 ± 0.004 pc) |
| 36 Oph C | |
| Radial velocity (Rv) | −0.04±0.22[5] km/s |
| Proper motion (μ) | RA: −479.573±0.031[5] mas/yr Dec.: −1124.332±0.020[5] mas/yr |
| Parallax (π) | 167.9617 ± 0.0311 mas[5] |
| Distance | 19.418 ± 0.004 ly (5.954 ± 0.001 pc) |
| Orbit | |
| 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) | 1,763.39 |
| Details | |
| 36 Oph A | |
| Radius | 0.817 ± 0.016[6] R☉ |
| Temperature | 4,843 ± 134[6] K |
| Metallicity [Fe/H] | –0.20[6] dex |
| Age | 0.6-1.8[7][8] Gyr |
| B | |
| Temperature | 4,985 ± 20[9] K |
| Metallicity [Fe/H] | –0.31 ± 0.042[9] dex |
| Other designations | |
36 Oph, WDS J17153-2636 | |
| AB: GJ 663, CD−26°12026, GCTP 3908.00, HIP 84405 | |
| A: Guniibuu, HR 6402, HD 155886, LHS 437, SAO 185198 | |
| B: HR 6401, HD 155885, LHS 438, SAO 185199 | |
| C: V2215 Ophiuchi, GJ 664, CD−26°12036, HD 156026, GCTP 3913.00, LHS 439, SAO 185213, HIP 84478 | |
| Database references | |
| SIMBAD | AB |
| A | |
| B | |
| C | |
| Exoplanet Archive | A |
| B | |
| C | |
| ARICNS | A |
| B | |
| C | |
  36 Location of 36 Ophiuchi in the constellation Ophiuchus | |
The primary and secondary stars (also known as HD 155886) are nearly identical orange main-sequence dwarfs of spectral type K2/K1. This binary is unusual because its eruptions do not seem to conform to the Waldmeier effect; that is, the strongest eruptions of HD 155886 are not the ones characterized by the fast eruption onset.[10] The tertiary star is an orange main-sequence dwarf of spectral type K5.
Star C is separated from the A-B pair by 700 arcseconds, compared to a minimum of 4.6 arcseconds for A-B, so its effect on the movements of the A-B pair is small. A and B have active chromospheres. At present the distance between the stars forming the AB-pair is 5.1 arcseconds and the position angle is 139 degrees, while star C is 731.6 arcseconds away from the A-component and situated at a position angle of 74 degrees.
Nomenclature
In the beliefs of the Kamilaroi and Euahlayi Aboriginal peoples in New South Wales, Australia, the star is called Guniibuu that represents the robin red-breast bird (Petroica boodang). In 2016, the IAU organized a Working Group on Star Names (WGSN)[11] 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.[12]
Hunt for substellar objects
The McDonald Observatory team has set limits to the presence of one or more planets[7] 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 (AU), although beyond 1.5 AU orbits are inherently unstable around either 36 Ophiuchi A or 36 Ophiuchi B.[13]
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.[14]
Notes
References
Further reading
External links
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