36 Ophiuchi


36 Ophiuchi, formally named Guniibuu, is a triple star system 19.5 light years from Earth. It is in the constellation Ophiuchus.
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 robin red-breast bird. In 2016, the IAU organized a Working Group on Star Names 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.

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, although beyond 1.5 AU orbits are inherently unstable around either 36 Ophiuchi A or 36 Ophiuchi B.
The star C 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.