- Source: Nu Octantis
ν Octantis, Latinised as Nu Octantis, is a star in the constellation of Octans. Unusually, it is the brightest star in this faint constellation at apparent magnitude +3.7. It is a spectroscopic binary star with a period around 2.9 years. Parallax measurements place it at 22.1 parsecs (72 ly) from Earth.
The primary has a spectral type of K1III, with the luminosity class III indicating that it is a giant star that has burned up the hydrogen at its core and has expanded. Nu Octantis A has 1.6 times the mass of the Sun, but has expanded to 5.8 times the radius of the Sun. Its photosphere has cooler to an effective temperature of 4,860 K and now is radiating 18 times as much luminosity as the Sun. It possibly hosts an extrasolar planet, a jovian planet on a retograde orbit.
The secondary star is likely either a red dwarf or a white dwarf, from its relatively low mass. This star is estimated to have around 60% the mass of the Sun. It shares a center of mass with the primary, completing an orbit around it every 2 years and 11 months. The orbit has an eccentricity of 0.24 and a semi-major axis of 2.63 au.
Planetary system
In 2009, the system was hypothesised to contain a superjovian exoplanet based on perturbations in the orbital period. A prograde solution was quickly ruled out but a retrograde solution remains a possibility, although the variations may instead be due to the secondary star being itself a close binary, since the formation of a planet in such a system would be difficult due to dynamic perturbations. Further evidence ruling out a stellar variability and favouring the existence of the planet was gathered by 2021.
See also
Gamma Cephei and Nu2 Canis Majoris, another similar-sized giant stars hosting a jovian planet
Beta Hydri
References
Kata Kunci Pencarian:
- Octans
- Nu Octantis
- Octans
- List of nearest giant stars
- List of star systems within 65–70 light-years
- Alpha Octantis
- List of exoplanet extremes
- Manfred Cuntz
- List of exoplanet firsts
- HD 59686 Ab
- Vega
