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36 Ophiuchi

Triple star system in the constellation Ophiuchus

Triple star system in the constellation Ophiuchus

B: C: | dec=A: B: C: B: K1V C: K5V | b-v= | u-b=

36 Ophiuchi (or Guniibuu for component A) is a triple star system 19.5 light-years from Earth in the constellation Ophiuchus.

Nomenclature

36 Ophiuchi is the system's Flamsteed designation. Component C (HD 156026) was also historically called 30 Scorpii.

In the culture of the Kamilaroi and Euahlayi Aboriginal peoples in New South Wales, Australia, the star is called Guniibuu and represents the robin red-breast bird (Petroica boodang). to catalog and standardize proper names for stars. The WGSN approved the name Guniibuu for 36 Ophiuchi A on 10 August 2018 and it is now so included in the List of IAU-approved Star Names.

Characteristics

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.

The tertiary star is an orange main-sequence dwarf of spectral type K5. The age for this star derived using gyrochronology is about 600 million years, while the age derived for the AB pair is 1.43 billion years. This discrepancy suggest that the A/B stars interacted with each other and slowed down their rotation periods, providing a spuriously higher age.

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.

Hunt for substellar objects

The McDonald Observatory team has set limits to the presence of one or more planets 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.

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. It presents a significant difference on proper motion measurements taken by the Hipparcos and Gaia spacecrafts, suggesting the presence of a giant planet.

Observation

On 26 October 2021, it was occulted by Venus as viewed from the Indian Ocean.

References

References

  1. {{Cite Gaia DR3. 4109030160308320128
  2. {{Cite Gaia DR3. 4109030160308317312
  3. {{Cite Gaia DR3. 4109034455276324608
  4. "IAU Working Group on Star Names (WGSN)".
  5. (2019). "Waldmeier Effect in Stellar Cycles". The Astrophysical Journal.
  6. Meeus, Jan. (2002). "More Mathematical Astronomy Morsels". Willmann-Bell.
  7. "ASAS-SN Variable Stars Database". ASAS-SN.
  8. (July 2006). "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample". [[The Astronomical Journal]].
  9. (2023-06-01). "Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets". [[The Astronomical Journal]].
  10. (2022-05-01). "A Monte Carlo Method for Evaluating Empirical Gyrochronology Models and Its Application to Wide Binary Benchmarks". [[The Astrophysical Journal]].
  11. (2025-06-26). "Astrometric Accelerations of Provisional Targets for the Habitable Worlds Observatory". The Astronomical Journal.
  12. (2019-10-01). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal.
  13. (1996). "36 Ophiuchi AB: Incompatibility of the Orbit and Precise Radial Velocities". Publications of the Astronomical Society of the Pacific.
  14. (2006). "Detection Limits from the McDonald Observatory Planet Search Program". Astronomical Journal.
  15. Tokovinin, Andrei. (July 2017). "Orbit Alignment in Triple Stars". The Astrophysical Journal.
  16. Luck, R. Earle. (2018-03-01). "Abundances in the Local Region. III. Southern F, G, and K Dwarfs". The Astronomical Journal.
  17. Luck, R. Earle. (2017-01-01). "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants". The Astronomical Journal.
  18. "IAU Catalog of Star Names".
  19. Wagman, M.. (August 1987). "Flamsteed's Missing Stars". Journal for the History of Astronomy.
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ophiuchus triple-star-systems flamsteed-objects k-type-main-sequence-stars solar-type-stars bright-star-catalogue-objects henry-draper-catalogue-objects hipparcos-objects durchmusterung-objects bayer-objects rs-canum-venaticorum-variables gliese-and-gj-objects objects-with-variable-star-designations stars-with-proper-names
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