21 Cancri

21 Cancri
Observation data; Epoch J2000 Equinox J2000
Constellation	Cancer
Right ascension	08h 23m 55.20829s
Declination	+10° 37′ 55.4169″
Apparent magnitude (V)	6.08
Characteristics
Spectral type	M2III
B−V color index	1.507±0.004
Variable type	suspected
Astrometry
Radial velocity (Rv)	4.53 km/s
Proper motion (μ)	RA: −0.843 mas/yr ; Dec.: −22.943 mas/yr
Parallax (π)	4.1258 ± 0.0272 mas
Distance	791 ± 5 ly ; (242 ± 2 pc)
Details
Radius	53 R☉
Luminosity	587 L☉
Temperature	3,885 K
Other designations
	NSV 17875, BD+11°1830, HD 70734, HIP 41163, HR 3290, SAO 97788
Database references
SIMBAD	data

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

^ ^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.
^ ^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.
^ ^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.
^ 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.
^ ^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.
^ ^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.
^ ^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.

Zdroj:https://en.wikipedia.org?pojem=21_Cancri
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[dr3-1] ^ ^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.

[ducati-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.

[abt-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.

[Anderson2012-4] 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.

[gcvs-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.

[dr2-6] ^ ^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.

[eggen-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.

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Observation data Epoch J2000 Equinox J2000
Constellation	Cancer
Right ascension	08^h 23^m 55.20829^s^[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 (R_v)	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]
Distance	791 ± 5 ly (242 ± 2 pc)

Details

Radius	53^[6] `R`_☉
Luminosity	587^[6] `L`_☉
Temperature	3,885^[6] K

Other designations
NSV 17875, BD+11°1830, HD 70734, HIP 41163, HR 3290, SAO 97788
Database references
SIMBAD	data