Nu Octantis

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ν Octantis
Octans constellation map.svg
Red circle.svg

Location of ν Octantis (circled)
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]
Spectral type K1III[3]
U−B color index +0.89[4]
B−V color index +1.00[4]
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) 45.25 ± 0.25[6] mas
Distance 72.1 ± 0.4 ly
(22.1 ± 0.1 pc)
Absolute magnitude (MV) +2.10[2]
Period (P) 1050.69+0.05
Semi-major axis (a) 2.62959+0.00009
Eccentricity (e) 0.23680 ± 0.00007
Inclination (i) 70.8 ± 0.9°
Longitude of the node (Ω) 87 ± 1.2°
Argument of periastron (ω)
74.970 ± 0.016°
Semi-amplitude (K1)
7.032 ± 0.003 km/s
Mass 1.04[8]
1.61 / 0.585[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 4860 ± 40[6] 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
Other designations
CD-77 1079, CCDM J21415-7723A, FK5 810, GC 30289, GJ 9744, HIP 107089, HR 8254, HD 205478, SAO 257948, WDS J21415-7723A
Database references

ν Octantis, Latinised as Nu Octantis. is a spectroscopic binary[9] star in the constellation Octans with a period around 2.9 years.[6] 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 a red dwarf from its low mass.[7]

In 2009, the system was hypothesized to contain an exoplanet based on perturbations in the orbital period.[6] A prograde solution was quickly ruled out[10] but a retrograde solution remains a possibility, although the variations may instead be due to the secondary star being itself a close binary,[11] since the formation of a planet in such a system would difficult due to dynamic perturbations.[12]

The Nu Octantis planetary system[7]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (unconfirmed) 2.1059 MJ 1.276 414.8 0.086 112.5°


  1. ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. Bibcode:2007A&A...474..653V. arXiv:0708.1752Freely accessible. doi:10.1051/0004-6361:20078357.  Vizier catalog entry
  2. ^ a b c d Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. Bibcode:2012AstL...38..331A. arXiv:1108.4971Freely accessible. doi:10.1134/S1063773712050015.  Vizier catalog entry
  3. ^ a b Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. Bibcode:2006AJ....132..161G. arXiv:astro-ph/0603770Freely accessible. doi:10.1086/504637. 
  4. ^ a b Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers. 42: 443. Bibcode:2014JAVSO..42..443M. Vizier catalog entry
  5. ^ Wilson, R. E. (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institution for Science. Bibcode:1953GCRV..C......0W. LCCN 54001336. 
  6. ^ a b c d Ramm, D. J.; Pourbaix, D.; Hearnshaw, J. B.; Komonjinda, S. (April 2009). "Spectroscopic orbits for K giants β Reticuli and ν Octantis: what is causing a low-amplitude radial velocity resonant perturbation in ν Oct?". Monthly Notices of the Royal Astronomical Society. 394 (3): 1695–1710. Bibcode:2009MNRAS.394.1695R. doi:10.1111/j.1365-2966.2009.14459.x. 
  7. ^ a b c d e f g h i j Ramm, D. J.; et al. (2016). "The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities". Monthly Notices of the Royal Astronomical Society. 460 (4): 3706–3719. Bibcode:2016MNRAS.460.3706R. arXiv:1605.06720Freely accessible. doi:10.1093/mnras/stw1106. 
  8. ^ a b Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555. Bibcode:1999A&A...352..555A. arXiv:astro-ph/9911002Freely accessible.  Vizier catalog entry
  9. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. Bibcode:2008MNRAS.389..869E. arXiv:0806.2878Freely accessible. doi:10.1111/j.1365-2966.2008.13596.x. 
  10. ^ Eberle, J.; Cuntz, M. (October 2010). "On the reality of the suggested planet in the ν Octantis system". The Astrophysical Journal. 721 (2): L168–L171. Bibcode:2010ApJ...721L.168E. doi:10.1088/2041-8205/721/2/L168. 
  11. ^ Morais, M. H. M.; Correia, A. C. M. (February 2012). "Precession due to a close binary system: an alternative explanation for ν-Octantis?". Monthly Notices of the Royal Astronomical Society. 419 (4): 3447–3456. Bibcode:2012MNRAS.419.3447M. arXiv:1110.3176Freely accessible. doi:10.1111/j.1365-2966.2011.19986.x. 
  12. ^ Gozdziewski, K.; Slonina, M.; Migaszewski, C.; Rozenkiewicz, A. (March 2013). "Testing a hypothesis of the ν Octantis planetary system". Monthly Notices of the Royal Astronomical Society. 430 (1): 533–545. Bibcode:2013MNRAS.430..533G. arXiv:1205.1341Freely accessible. doi:10.1093/mnras/sts652.