61 Cancri

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61 Cancri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cancer
Right ascension 08h 57m 58.66668s[1]
Declination +30° 14′ 01.7715″[1]
Apparent magnitude (V) +6.290[2] (7.0 + 7.0)[3]
Spectral type F4V[4]
U−B color index −0.04[5]
B−V color index +0.42[5]
Radial velocity (Rv) +10.1±0.3[2] km/s
Proper motion (μ) RA: +48.10[1] mas/yr
Dec.: +27.48[1] mas/yr
Parallax (π) 18.01 ± 0.52[1] mas
Distance 181 ± 5 ly
(56 ± 2 pc)
61 Cnc A
Mass 1.40[3] M
Surface gravity (log g) 3.87[6] cgs
Temperature 6,396[6] K
Metallicity [Fe/H] −0.34[2] dex
Rotational velocity (v sin i) 5[7] km/s
Age 2.5[2] Gyr
61 Cnc B
Mass 1.40[3] M
Other designations
61 Cancri, BD+30°1795, HD 76572, HIP 44031, HR 3563, SAO 61157.[8]

61 Cancri (61 Cnc) is the Flamsteed designation for a visual binary[3] star system in the northern constellation Cancer. The pair have a combined apparent magnitude of 6.25, which means 61 Cancri is faintly visible to the naked eye. (According to the Bortle scale, it can be seen from rural or even dark suburban skies.) Based upon parallax measurements, the system is approximately 181 light years away from Earth.

The two components appear to be roughly identical[9] with individual masses of about 1.4[3] times that of the Sun and apparent magnitudes of 7.0.[3] Their combined stellar classification is F4V,[4] matching that of an F-type main sequence star. They have an angular separation of 0.300 along a position angle of 129.0° (as of 2014). The pair orbit each other with an estimated period of 40.657 years.[3] No significant level of chromospheric activity has been detected coming from either star.[9]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Nordström, B.; et al. (May 2014), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ~14000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv:astro-ph/0405198Freely accessible, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959. 
  3. ^ a b c d e f g Tokovinin, Andrei (April 2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal, 147 (4): 14, arXiv:1401.6827Freely accessible, Bibcode:2014AJ....147...87T, doi:10.1088/0004-6256/147/4/87, 87. 
  4. ^ a b Abt, Helmut A. (May 2008), "Visual Multiples. IX. MK Spectral Types", The Astrophysical Journal Supplement Series, 176 (1): 216–217, Bibcode:2008ApJS..176..216A, doi:10.1086/525529. 
  5. ^ a b Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data, Bibcode:1986EgUBV........0M. 
  6. ^ a b David, Trevor J.; Hillenbrand, Lynne A. (May 2015), "The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 38, arXiv:1501.03154Freely accessible, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, 146. 
  7. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities.", Contributi Osservatorio Astronomico di Padova in Asiago, 239, Bibcode:1970CoAsi.239....1B. 
  8. ^ "61 Cnc -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg. 
  9. ^ a b Radick, Richard R.; Lockwood, G. W.; Skiff, B. A.; Baliunas, S. L. (September 1998), "Patterns of Variation among Sun-like Stars", The Astrophysical Journal Supplement Series, 118 (1): 239–258, Bibcode:1998ApJS..118..239R, doi:10.1086/313135.