Kappa Cancri

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Kappa Cancri
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cancer
Right ascension  08h 20m 32.13630s[1]
Declination +24° 01′ 20.3198″[1]
Apparent magnitude (V) +5.233[2]
Spectral type B8 IIIp[3]
B−V color index −0.113[2]
Variable type α2 CVn[4]
Proper motion (μ) RA: −20.29[1] mas/yr
Dec.: −18.81[1] mas/yr
Parallax (π)7.13 ± 0.38[1] mas
Distance460 ± 20 ly
(140 ± 7 pc)
Absolute magnitude (MV)−0.82[5]
Period (P)6.3933 d
Eccentricity (e)0.13
Periastron epoch (T)2440001.95 JD
Argument of periastron (ω)
Semi-amplitude (K1)
67.4 km/s
κ Cnc A
Mass4.5 M
Radius5.0 R
Luminosity322[5] L
Surface gravity (log g)3.7±0.1[2] cgs
Temperature12,800±200[2] K
Metallicity [Fe/H]+0.51[5] dex
Rotational velocity (v sin i)6±2[2] km/s
κ Cnc B
Mass2.1 M
Radius2.4 R
Surface gravity (log g)4.0 cgs
Temperature8,500 K
Rotational velocity (v sin i)40 km/s
Other designations
κ Cnc, 76 Cancri, BD+11° 1984, FK5 1238, HD 78316, HIP 44798, HR 3623, SAO 98378[8]
Database references

Kappa Cancri, Latinized from κ Cancri, is a blue-white hued binary star system in the zodiac constellation of Cancer. It is faintly visible to the naked eye with an apparent visual magnitude of +5.23.[2] The magnitude difference between the two stars is about 2.6.[9] Based upon an annual parallax shift of 7.13 mas as seen from the Earth,[1] the system is located roughly 460 light years from the Sun.

This is a single-lined spectroscopic binary[2] star system with an orbital period of 6.39 days and an eccentricity of 0.13.[6] The primary, component A, has a stellar classification of B8 IIIp,[3] suggesting it is a B-type giant star, it a mercury-manganese star, a type of chemically peculiar star showing large overabundances of those two elements in the outer atmosphere.[2] It is classified as an Alpha2 Canum Venaticorum type variable star and its brightness varies from magnitude +5.22 to +5.27 with a period of 5 days.[4]

The primary component has 4.5 times the mass of the Sun, 5 times the Sun's radius, and an effective temperature of 13,200 K. The secondary, component B, is a smaller star with 2.1 times the mass and 2.4 times the radius of the Sun, having an effective temperature of 8,500 K.[7]


  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.
  2. ^ a b c d e f g h Maza, Natalia L.; et al. (December 2014), "A non-LTE spectral analysis of the 3He and 4He isotopes in the HgMn star κ Cancri", Astronomy & Astrophysics, 572: 7, arXiv:1412.2052, Bibcode:2014A&A...572A.112M, doi:10.1051/0004-6361/201425037, A112.
  3. ^ a b Levato, H. (1975), "Rotational velocities and spectral types for a sample of binary systems", Astronomy and Astrophysics, 19: 91, Bibcode:1975A&AS...19...91L.
  4. ^ a b Samus', N. N.; et al. (January 2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085.
  5. ^ a b c 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.
  6. ^ a b Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
  7. ^ a b Ryabchikova, T. (April 1998), "Abundance analysis of SB2 binary stars with HgMn primaries", Contributions of the Astronomical Observatory Skalnate Pleso, 27 (3): 319–323, arXiv:astro-ph/9805063, Bibcode:1998CoSka..27..319R.
  8. ^ "kap Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-19.
  9. ^ Ryabchikova, T.; et al. (April 1998), "Discovery of the secondary star of the HgMn binary kappa CANCRI", Contributions of the Astronomical Observatory Skalnate Pleso, 27 (3): 258–260, arXiv:astro-ph/9805143, Bibcode:1998CoSka..27..258R.