Brightest star in the constellation Octans
ν Octantis
Location of ν Octantis in Octans (circled)
Observation dataEpoch 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
A
Evolutionary stage
Giant star
Spectral type
K1III[ 3]
U−B color index
+0.89[ 4]
B−V color index
+1.00[ 4]
B
Evolutionary stage
Either a main sequence star or a white dwarf [ 5]
Spectral type
K7–M0V or WD[ 5]
Astrometry Radial velocity (Rv )+34.40[ 6] km/s Proper motion (μ) RA: +68.656 mas /yr [ 7] Dec.: −250.044 mas /yr [ 7] Parallax (π)51.5172 ± 0.6525 mas [ 7] Distance 63.3 ± 0.8 ly (19.4 ± 0.2 pc ) Absolute magnitude (MV ) 2.3± 0.16[ 5]
Orbit [ 8] 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[ 9] 1.61[ 8] M ☉ Radius 5.9[ 9] 5.81± 0.12[ 8] R ☉ Luminosity 17.53[ 2] L ☉ Surface gravity (log g ) 3.12± 0.10[ 8] cgs Temperature 4,860± 40[ 10] K Metallicity [Fe/H] +0.18± 0.04[ 8] dex Rotational velocity (v sin i )2.0[ 8] km/s Age ~2.5-3[ 8] Gyr Nu Octantis B[ 5] Mass 0.585[ 8] M ☉
Other designations nu Oct,
CD −77 1079,
CCDM J21415-7723,
FK5 810,
GC 30289,
GJ 9744,
HIP 107089,
HR 8254,
HD 205478,
SAO 257948,
WDS J21415-7723
Database references SIMBAD data
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.[ 2] It is a spectroscopic binary [ 11] star with a period around 2.9 years.[ 10] Parallax measurements place it at 19.4 parsecs (63 ly) from Earth.[ 7]
The primary has a spectral type of K1III,[ 3] 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 .[ 8] Its photosphere has cooler to an effective temperature of 4,860 K [ 10] and now is radiating 18 times as much luminosity as the Sun.[ 2] It possibly hosts an extrasolar planet , a jovian planet on a retograde orbit.[ 5]
The secondary star is likely either a red dwarf or a white dwarf , from its relatively low mass.[ 5] 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 .[ 8]
^ a b Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics . 474 (2): 653–664. arXiv :0708.1752 . Bibcode :2007A&A...474..653V . doi :10.1051/0004-6361:20078357 . S2CID 18759600 . Vizier catalog entry
^ a b c d Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters . 38 (5): 331. arXiv :1108.4971 . Bibcode :2012AstL...38..331A . doi :10.1134/S1063773712050015 . S2CID 119257644 . Vizier catalog entry
^ 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. arXiv :astro-ph/0603770 . Bibcode :2006AJ....132..161G . doi :10.1086/504637 . S2CID 119476992 .
^ a b Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers . 42 (2): 443. Bibcode :2014JAVSO..42..443M . Vizier catalog entry
^ a b c d e f Cite error: The named reference Ramm3
was invoked but never defined (see the help page ).
^ Wilson, R. E. (1953). "General Catalogue of Stellar Radial Velocities". Carnegie Institute Washington D.C. Publication . Carnegie Institution for Science . Bibcode :1953GCRV..C......0W . LCCN 54001336 .
^ a b c Brown, A. G. A. ; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties" . Astronomy & Astrophysics . 616 . A1. arXiv :1804.09365 . Bibcode :2018A&A...616A...1G . doi :10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR .
^ 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. arXiv :1605.06720 . Bibcode :2016MNRAS.460.3706R . doi :10.1093/mnras/stw1106 .
^ 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 : 555–562. arXiv :astro-ph/9911002 . Bibcode :1999A&A...352..555A . Vizier catalog entry
^ a b c Cite error: The named reference Ramm
was invoked but never defined (see the help page ).
^ 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. arXiv :0806.2878 . Bibcode :2008MNRAS.389..869E . doi :10.1111/j.1365-2966.2008.13596.x . S2CID 14878976 .