20 Cygni

20 Cygni

Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus
Right ascension	19^h 50^m 37.72371^s[1]
Declination	+52° 59′ 16.7901″[1]
Apparent magnitude (V)	5.030[2]
Characteristics
Spectral type	K3 III CN2[3]
B−V color index	1.280[2]
Astrometry
Radial velocity (Rv)	−22.04±0.15[4] km/s
Proper motion (μ)	RA: −10.29[1] mas/yr Dec.: −69.68[1] mas/yr
Parallax (π)	16.11 ± 0.14 mas[1]
Distance	202 ± 2 ly (62.1 ± 0.5 pc)
Details
Mass	1.28[2] M☉
Radius	13[5] R☉
Luminosity	57.5[2] L☉
Surface gravity (log g)	2.2[5] cgs
Temperature	4,337±67[2] K
Metallicity [Fe/H]	+0.14[5] dex
Rotational velocity (v sin i)	4.6[5] km/s
Other designations
d Cyg, 20 Cyg, BD+52°2547, FK5 3586, HD 188056, HIP 97635, HR 7576, SAO 32042[6]
Database references
SIMBAD	data

20 Cygni is a single,^[7] orange-hued star in the northern constellation of Cygnus. It is a faint star but is visible to the naked eye with an apparent visual magnitude of 5.03.^[2] The distance to 20 Cygni can be estimated from its annual parallax shift of 16 mas,^[1] which yields a range of 202 light years. It is moving closer to the Earth with a heliocentric radial velocity of −22 km/s.^[4]

This is an aging red giant star with a stellar classification of K3 III CN2,^[3] a star that has used up its core hydrogen and is expanding. The suffix notation indicates there are unusually strong lines of cyanogen in the spectrum. 20 Cyg is listed as one of the least variable stars in the Hipparcos catalogue, changing its brightness by no more than 0.01 magnitude.^[8] It has 1.28^[2] times the mass of the Sun and has expanded to 13^[5] times the Sun's radius. The star is radiating 57.5 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,337 K.^[2]

References

1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal, 150 (3), 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114.
3. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373
4. 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.
5. Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 Hipparcos Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
6. "20 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-09.
7. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
8. Adelman, S. J. (2001), "Research Note Hipparcos photometry: The least variable stars", Astronomy and Astrophysics, 367: 297–298, Bibcode:2001A&A...367..297A, doi:10.1051/0004-6361:20000567.