Omega2 Cancri

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ω2 Cancri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cancer
Right ascension  08h 01m 43.75679s[1]
Declination +25° 05′ 22.0823″[1]
Apparent magnitude (V) 6.32[2]
Evolutionary stage main sequence[3]
Spectral type A1 V[4]
B−V color index 0.023±0.006[2]
Radial velocity (Rv)−7.6±2.5[5] km/s
Proper motion (μ) RA: −25.112[1] mas/yr
Dec.: +12.038[1] mas/yr
Parallax (π)7.4046 ± 0.0486[1] mas
Distance440 ± 3 ly
(135.1 ± 0.9 pc)
Absolute magnitude (MV)0.51[2]
Mass2.59±0.06[3] M
Radius2.5[6] R
[3] L
[3] K
Rotational velocity (v sin i)159[3] km/s
Other designations
ω2 Cancri, 4 Cnc, BD+25°1816, HD 65856, HIP 39263, HR 3132, SAO 79869, CCDM J08017+2506A, WDS J08017+2505A, GSC 01930-00674[7]
Database references

ω2 Cancri is a star in the zodiac constellation Cancer, located around 810 light years away from the Sun. It has the Flamsteed designation 4 Cancri; ω2 Cancri is the Bayer designation, which is Latinised to omega2 Cancri and abbreviated to ω2 Cnc or omega2 Cnc; the star is near the lower limit of visibility to the naked eye, having an apparent visual magnitude of 6.32.[2] It is moving closer to the Earth with a heliocentric radial velocity of −8 km/s;[5] the position of this star near the ecliptic means it is subject to lunar occultations.[8]

This is an ordinary A-type main-sequence star with a stellar classification of A1 V,[4] which indicates it is generating energy through hydrogen fusion at its core, it has 2.6[3] times the mass of the Sun and about 2.5[6] times the Sun's radius. The star is radiating 68[3] times the Sun's luminosity from its photosphere at an effective temperature of 9354 K.[3]


  1. ^ a b c d e 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.
  2. ^ 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.
  3. ^ a b c d e f g h Zorec, J.; et al. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy and Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691.
  4. ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  5. ^ a b de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  6. ^ a b Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  7. ^ "ome02 Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-02-23.
  8. ^ Schmidtke, P. C.; Africano, J. L. (2011), "KPNO Lunar Occultation Summary. III", The Astronomical Journal, 141: 10, Bibcode:2011AJ....141...10S, doi:10.1088/0004-6256/141/1/10.