ν Octantis, Latinised as Nu Octantis, is the brightest star in the constellation of Octans. It is a spectroscopic binary[11] star with a period around 2.9 years.[9] Its apparent magnitude is 3.73.[2] Located around 21.20 parsecs (69.1 ly) distant,[1] the primary is an orange giant of spectral type K1III,[3] a star that has used up its core hydrogen and has expanded. The secondary star is likely either a red dwarf or a white dwarf, from its relatively low mass.[10]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Octans |
Right ascension | 21h 41m 28.64977s[1] |
Declination | −77° 23′ 24.1563″[1] |
Apparent magnitude (V) | 3.73[2] |
Characteristics | |
Spectral type | K1III[3] |
U−B color index | +0.89[4] |
B−V color index | +1.00[4] |
Astrometry | |
Radial velocity (Rv) | +34.40[5] km/s |
Proper motion (μ) | RA: +66.41[1] mas/yr Dec.: −239.10[1] mas/yr |
Parallax (π) | 51.5172 ± 0.6525 mas[6] |
Distance | 63.3 ± 0.8 ly (19.4 ± 0.2 pc) |
Absolute magnitude (MV) | +2.10[2] +2.02[7] |
Orbit[7] | |
Period (P) | 1050.69+0.05 −0.07 d |
Semi-major axis (a) | 2.62959+0.00009 −0.00011 AU |
Eccentricity (e) | 0.23680±0.00007 |
Inclination (i) | 70.8±0.9° |
Longitude of the node (Ω) | 87±1.2° |
Argument of periastron (ω) (secondary) | 74.970±0.016° |
Semi-amplitude (K1) (primary) | 7.032±0.003 km/s |
Details | |
Nu Octantis A | |
Mass | 1.04[8] 1.61[7] M☉ |
Radius | 5.9[8] 5.81±0.12[7] R☉ |
Luminosity | 17.53[2] L☉ |
Surface gravity (log g) | 3.12±0.10[7] cgs |
Temperature | 4,860±40[9] K |
Metallicity [Fe/H] | +0.18±0.04[7] dex |
Rotational velocity (v sin i) | 2.0[7] km/s |
Age | ~2.5-3[7] Gyr |
Nu Octantis B[10] | |
Mass | 0.585[7] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
In 2009, the system was hypothesised to contain a superjovian exoplanet based on perturbations in the orbital period.[9] A prograde solution was quickly ruled out[12] but a retrograde solution remains a possibility, although the variations may instead be due to the secondary star being itself a close binary,[13] since the formation of a planet in such a system would difficult due to dynamic perturbations.[14] Further evidence ruling out a stellar variability and favouring the existence of the planet was gathered by 2021.[10]
Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | 2.1059 MJ | 1.276 | 414.8 | 0.086 | 112.5° | — |