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21 Cancri is a double star in the northern zodiac constellation of Cancer. It is just visible to the naked eye as a dim, red-hued star with an apparent visual magnitude of 6.08.[2] The star is located around 791 light years away from the Sun, based on parallax. It is moving further from the Earth with a heliocentric radial velocity of 35 km/s.[6]

21 Cancri
Observation data
Epoch J2000      Equinox J2000
Constellation Cancer
Right ascension 08h 23m 55.20829s[1]
Declination +10° 37′ 55.4169″[1]
Apparent magnitude (V) 6.08[2]
Characteristics
Spectral type M2III[3]
B−V color index 1.507±0.004[4]
Variable type suspected[5]
Astrometry
Radial velocity (Rv)4.53[1] km/s
Proper motion (μ) RA: −0.843[1] mas/yr
Dec.: −22.943[1] mas/yr
Parallax (π)4.1258 ± 0.0272 mas[1]
Distance791 ± 5 ly
(242 ± 2 pc)
Details
Radius53[6] R☉
Luminosity587[6] L☉
Temperature3,885[6] K
Other designations
NSV 17875, BD+11°1830, HD 70734, HIP 41163, HR 3290, SAO 97788
Database references
SIMBADdata

The brighter component is an aging red giant with a stellar classification of M2III.[3] It is currently on the asymptotic giant branch, indicating this is a highly evolved star that has exhausted both its core hydrogen and core helium.[7] This is a suspected variable star.[5] It has expanded to 53[6] times the radius of the Sun and is radiating 587[6] times the Sun's luminosity from its swollen photosphere at an effective temperature of 3,885 K.[6] A 9th magnitude companion star is located one arc second away.[7]


References


  1. Vallenari, A.; et al. (Gaia Collaboration) (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. arXiv:2208.00211. doi:10.1051/0004-6361/202243940. Gaia DR3 record for this source at VizieR.
  2. Ducati, J. R. (2002). "VizieR On-line Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". VizieR On-line Data Catalog. Bibcode:2002yCat.2237....0D.
  3. Abt, H. A. (1985). "Visual multiples. VIII. 1000 MK types". The Astrophysical Journal Supplement Series. 59: 95. Bibcode:1985ApJS...59...95A. doi:10.1086/191064.
  4. 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.
  5. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/GCVS. Bibcode:2009yCat....102025S.
  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. Eggen, Olin J. (1992). "Asymptotic Giant Branch Stars Near the Sun". The Astronomical Journal. 104: 275. Bibcode:1992AJ....104..275E. doi:10.1086/116239.

На других языках

- [en] 21 Cancri

[ru] 21 Рака

21 Рака (лат. 21 Cancri) — двойная звезда, которая находится в созвездии Рака. Главный компонент, 21 Рака А, — красный гигант спектрального класса М.


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