Nu2 Canis Majoris

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ν2 Canis Majoris
Canis Major constellation map.svg
Red circle.svg
Location of ν2 Canis Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Canis Major
Right ascension  06h 36m 41.03758s[1]
Declination −19° 15′ 21.1659″[1]
Apparent magnitude (V) 3.96[2]
Spectral type K1 III[2]
Radial velocity (Rv)+2.57±0.14[3] km/s
Proper motion (μ) RA: +62.57±0.15[1] mas/yr
Dec.: −69.97±0.16[1] mas/yr
Parallax (π)50.63 ± 0.23[1] mas
Distance64.4 ± 0.3 ly
(19.75 ± 0.09 pc)
Absolute magnitude (MV)2.47[2]
Mass1.3±0.1 M
Radius4.9±0.1 R
Luminosity11.3±0.1 L
Surface gravity (log g)3.18±0.03 cgs
Temperature4,790±27 K
Metallicity [Fe/H]0.21±0.10 dex
Rotational velocity (v sin i)1.97±0.23[3] km/s
Age4.6±0.7 Gyr
Other designations
ν2 CMa, 7 CMa, BD−19°1502, FK5 2510, GC 8624, GJ 239.1, HD 47205, HIP 31592, HR 2429, SAO 151702
Database references

Nu2 Canis Majoris2 Canis Majoris) is a single[5] star in the southern constellation of Canis Major.


With an apparent visual magnitude of 3.96,[2] it is bright enough to be seen with the naked eye to the southwest of Sirius. It has an annual parallax shift of around 50.63 mas as seen from Earth,[1] thus this system is about 64.4 light years from the Sun, a parallax well within the error margins of the figure later given by the Gaia space observatory data release 2, namely 50.471 ± 0.4168.[6]

It is an evolved K-type giant around 4.6 billion years old. Around 1.3 times as massive as the Sun, it has expanded to around 4.9 times the Sun's diameter and 11 times its luminosity.[4] In 2011, it was found to have a planet.[7]

Chinese name[edit]

In Chinese astronomy, ν2 Canis Majoris is called 野雞, Pinyin: Yějī, meaning Wild Cockerel, because this star is marking itself and stand alone in Wild Cockerel asterism, Well mansion (see : Chinese constellation).[8] 野雞 (Yějī), westernized into Ya Ke. According to R.H. Allen opinion, the name Ya Ke is asterism consisting ο1 Canis Majoris and π Canis Majoris, with other small stars in the body of the Dog[9]

Planetary system[edit]

By measuring periodic variations in the radial velocity of the host star between 2009 and 2010, the Pan-Pacific Planet Search program was able to identify a planet orbiting Nu2 Canis Majoris. An orbital fit produced a minimum mass estimate of 2.6±0.6 MJwith an orbital period of 2.1 years and an eccentricity of 0.23. Star spots were ruled out as a source for the signal with a false-alarm probability of 98.7%.[7] Further observations through 2019 detected the planet, as well as a secondary planet c in a 4:3 orbital resonance with planet b.[10]

The Nu2 Canis Majoris planetary system[10]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b ≥1.895 MJ 1.761 736.9 0.055
c ≥0.609 MJ 2.143 988.9 0.046


  1. ^ a b c d e f 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. Vizier catalog entry
  2. ^ a b c d Setiawan, J.; et al. (July 2004), "Precise radial velocity measurements of G and K giants. Multiple systems and variability trend along the Red Giant Branch", Astronomy and Astrophysics, 421: 241–254, Bibcode:2004A&A...421..241S, doi:10.1051/0004-6361:20041042-1.
  3. ^ a b Jofré, E.; et al. (2015), "Stellar parameters and chemical abundances of 223 evolved stars with and without planets", Astronomy & Astrophysics, 574: A50, arXiv:1410.6422, Bibcode:2015A&A...574A..50J, doi:10.1051/0004-6361/201424474.
  4. ^ a b Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575. A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951.
  5. ^ 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.
  6. ^ 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.
  7. ^ a b Wittenmyer; et al. (2011). "The Pan-Pacific Planet Search. I. A Giant Planet Orbiting 7 CMa". The Astrophysical Journal. 743 (2): 184. arXiv:1111.1007. Bibcode:2011ApJ...743..184W. doi:10.1088/0004-637X/743/2/184.
  8. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 16 日
  9. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Canis Major
  10. ^ a b Luque, R.; Trifonov, T.; Reffert, S.; Quirrenbach, A.; Lee, M. H.; Albrecht, S.; Andersen, M. Fredslund; Antoci, V.; Grundahl, F.; Schwab, C.; Wolthoff, V. (13 October 2019). "Precise radial velocities of giant stars XIII. A second Jupiter orbiting in 4:3 resonance in the 7 CMa system". Astronomy & Astrophysics. A136: 631. arXiv:1910.05853. Bibcode:2019arXiv191005853L. doi:10.1051/0004-6361/201936464.

External links[edit]