17 Cygni

17 Cygni is the Flamsteed designation for a multiple star system^[3] in the northern constellation of Cygnus. It has an apparent visual magnitude of 5.00,^[2] so, according to the Bortle scale, it is visible from suburban skies at night. Measurements of the annual parallax find a shift of 0.0477″,^[1] which is equivalent to a distance of around 68.5 ly (21.0 pc) from the Sun. It has a relatively high proper motion, traversing the celestial sphere at the rate of 0.451″/year.^[11]

17 Cygni

Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus
Right ascension	19h 46m 25.600s[1]
Declination	+33° 43′ 39.35″[1]
Apparent magnitude (V)	5.00[2] + 8.56[3]
Characteristics
Spectral type	F7 V[2] + K6 V + K3 V + K3 V[3] + M0.4[4]
B−V color index	0.46[2]
Astrometry
Radial velocity (Rv)	+4.1[5] km/s
Proper motion (μ)	RA: +22.745 mas/yr[1] Dec.: –448.311 mas/yr[1]
Parallax (π)	47.6516 ± 0.0675 mas[1]
Distance	68.45 ± 0.10 ly (20.99 ± 0.03 pc)
Absolute magnitude (MV)	3.40[2]
Details
17 Cyg A
Mass	1.24[6] M☉
Radius	1.538[7] R☉
Luminosity	3.66[8] L☉
Surface gravity (log g)	4.262[8] cgs
Temperature	6,455[8] K
Metallicity [Fe/H]	0.027[8] dex
Rotational velocity (v sin i)	9[2] km/s
Age	2.8[9] Gyr
17 Cyg B
Mass	0.65 M☉
Other designations
17 Cyg, BD+33°3587, GJ 9670, HD 187013, HIP 97295, HR 7534, SAO 68827[10]
Database references
SIMBAD	data

This system consists of two visual binary systems that were discovered by John Herschel in the 1820s. Components A and B form a bright, wide pair with an angular separation of 26.0 arcsecond and an estimated orbital period of ~6,200 years. The faint, close system consists of components F and G with a separation of 2.6 arcsecond and a period of 238 years. The two binaries form a hierarchical system with a separation of about 800 arcseconds and orbital period of 3.7 million years or more.^[3] At an angular separation of 791.40 arcseconds is a proper motion companion with a classification of M0.4, indicating this is a red dwarf star. At the estimated distance of the pair, this is equal to a projected separation of 16,320 AU.^[4] Although the CCDM lists four other companions, these are not associated with the system.^[12]

The stellar classification of the primary star, component A, is F7 V,^[2] which means it is a main sequence star like the Sun. The star has 1.24^[6] times the mass of the Sun and 1.54^[7] times the Sun's radius. It is some 2.8^[9] billion years old and shines with 3.66^[8] times the Sun's luminosity. The effective temperature of the stellar atmosphere is 6,455^[8] K, giving it the yellow-white hued glow of an F-type star.^[13]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
2. Takeda, Yoichi; et al. (February 2005), "High-Dispersion Spectra Collection of Nearby F--K Stars at Okayama Astrophysical Observatory: A Basis for Spectroscopic Abundance Standards", Publications of the Astronomical Society of Japan, 57 (1): 13–25, Bibcode:2005PASJ...57...13T, doi:10.1093/pasj/57.1.13.
3. Romanenko, L. G. (March 2017), "A dynamical study of the multiple system 17 Cygni ABFG", Astronomy Reports, 61 (3): 206–220, Bibcode:2017ARep...61..206R, doi:10.1134/S1063772917020056, S2CID 255199959.
4. Dhital, Saurav; et al. (June 2010), "Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES): A Catalog of Very Wide, Low-mass Pairs", The Astronomical Journal, 139 (6): 2566–2586, arXiv:1004.2755, Bibcode:2010AJ....139.2566D, doi:10.1088/0004-6256/139/6/2566, S2CID 661494.
5. Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14,000 F and G dwarfs", Astronomy and Astrophysics, 418 (3): 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959, S2CID 11027621.
6. Halbwachs, J. -L; et al. (2018), "Multiplicity among solar-type stars. IV. The CORAVEL radial velocities and the spectroscopic orbits of nearby K dwarfs", Astronomy and Astrophysics, 619: A81, arXiv:1808.04605, Bibcode:2018A&A...619A..81H, doi:10.1051/0004-6361/201833377, S2CID 119437322.
7. Schofield, Mathew; et al. (2019), "The Asteroseismic Target List for Solar-like Oscillators Observed in 2 minute Cadence with the Transiting Exoplanet Survey Satellite", The Astrophysical Journal Supplement Series, 241 (1): 12, arXiv:1901.10148, Bibcode:2019ApJS..241...12S, doi:10.3847/1538-4365/ab04f5, S2CID 119481586.
8. Takeda, Yoichi (April 2007), "Fundamental Parameters and Elemental Abundances of 160 F-G-K Stars Based on OAO Spectrum Database", Publications of the Astronomical Society of Japan, 59 (2): 335–356, Bibcode:2007PASJ...59..335T, doi:10.1093/pasj/59.2.335.
9. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
10. "* 17 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2013-10-26.
11. Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal, 129 (3): 1483–1522, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854, S2CID 2603568.
12. Phillips, N. M.; et al. (April 2010), "Target selection for the SUNS and DEBRIS surveys for debris discs in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 403 (3): 1089–1101, arXiv:0911.3426, Bibcode:2010MNRAS.403.1089P, doi:10.1111/j.1365-2966.2009.15641.x, S2CID 119262858. See the note for F094.
13. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16.