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| constell = [[Cancer (constellation)|Cancer]]
| constell = [[Cancer (constellation)|Cancer]]
| epoch = J2000
| epoch = J2000
| ra = {{RA|08|23|55.20938}}<ref name=hipparcos/>
| ra = {{RA|08|23|55.20829}}<ref name=dr3/>
| dec = {{DEC|+10|37|55.4040}}<ref name=hipparcos/>
| dec = {{DEC|+10|37|55.4169}}<ref name=dr3/>
| appmag_v = 6.08<ref name=ducati/>
| appmag_v = 6.08<ref name=ducati/>
}}
}}
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}}
}}
{{Starbox astrometry
{{Starbox astrometry
| radial_v = 34.65<ref name=dr2/>
| radial_v = 4.53<ref name=dr3/>
| prop_mo_ra = {{val|-0.730}}<ref name=dr2/>
| prop_mo_ra = {{val|-0.843}}<ref name=dr3/>
| prop_mo_dec = {{val|-23.274}}<ref name=dr2/>
| prop_mo_dec = {{val|-22.943}}<ref name=dr3/>
| parallax = 4.0080
| parallax = 4.1258
| p_error = 0.0989
| p_error = 0.0272
| parallax_footnote = <ref name=dr2/>
| parallax_footnote = <ref name=dr3/>
| absmag_v =
| absmag_v =
}}
}}
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{{Starbox end}}
{{Starbox end}}


'''21 Cancri''' is a [[double star]] in the northern [[zodiac]] [[constellation]] of [[Cancer (constellation)|Cancer]]. It is just visible to the naked eye as a dim, red-hued star with an [[apparent visual magnitude]] of 6.08.<ref name=ducati/> The star is located around 820&nbsp;[[light year]]s away from the Sun, based on [[stellar parallax|parallax]]. It is moving further from the Earth with a heliocentric [[radial velocity]] of 35&nbsp;km/s.<ref name=dr2/>
'''21 Cancri''' is a [[double star]] in the northern [[zodiac]] [[constellation]] of [[Cancer (constellation)|Cancer]]. It is just visible to the naked eye as a dim, red-hued star with an [[apparent visual magnitude]] of 6.08.<ref name=ducati/> The star is located around 791&nbsp;[[light year]]s away from the Sun, based on [[stellar parallax|parallax]]. It is moving further from the Earth with a heliocentric [[radial velocity]] of 35&nbsp;km/s.<ref name=dr2/>


The brighter component is an aging [[red giant]] with a [[stellar classification]] of M2III.<ref name=abt/> It is currently on the [[asymptotic giant branch]], indicating this is a highly [[stellar evolution|evolved]] star that has exhausted both its core hydrogen and core helium.<ref name=eggen/> This is a suspected [[variable star]].<ref name=gcvs/> It has expanded to 53<ref name=dr2/> times the [[radius of the Sun]] and is radiating 587<ref name=dr2/> times the [[Sun's luminosity]] from its swollen [[photosphere]] at an [[effective temperature]] of 3,885&nbsp;K.<ref name=dr2/> A 9th magnitude companion star is located one [[arc second]] away.<ref name=eggen/>
The brighter component is an aging [[red giant]] with a [[stellar classification]] of M2III.<ref name=abt/> It is currently on the [[asymptotic giant branch]], indicating this is a highly [[stellar evolution|evolved]] star that has exhausted both its core hydrogen and core helium.<ref name=eggen/> This is a suspected [[variable star]].<ref name=gcvs/> It has expanded to 53<ref name=dr2/> times the [[radius of the Sun]] and is radiating 587<ref name=dr2/> times the [[Sun's luminosity]] from its swollen [[photosphere]] at an [[effective temperature]] of 3,885&nbsp;K.<ref name=dr2/> A 9th magnitude companion star is located one [[arc second]] away.<ref name=eggen/>
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<ref name=dr2>{{cite DR2|600978285351788800}}</ref>
<ref name=dr2>{{cite DR2|600978285351788800}}</ref>


<ref name=hipparcos>{{cite journal
<ref name=dr3>{{cite Gaia DR3|600978285351788800}}</ref>
| title=Validation of the new Hipparcos reduction
| last1=van Leeuwen | first1=F.
| journal=Astronomy and Astrophysics
| volume=474 | issue=2 | pages=653–664 | date=2007
| arxiv=0708.1752 | bibcode=2007A&A...474..653V
| doi=10.1051/0004-6361:20078357 | s2cid=18759600 }}</ref>


<ref name=Anderson2012>{{cite journal
<ref name=Anderson2012>{{cite journal

Revision as of 15:18, 23 August 2022

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

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]

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. ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b 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. ^ a b 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. ^ a b 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. ^ a b c d e f g 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 Eggen, Olin J. (1992). "Asymptotic Giant Branch Stars Near the Sun". The Astronomical Journal. 104: 275. Bibcode:1992AJ....104..275E. doi:10.1086/116239.
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