Astronomy:Eta Cygni

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Short description: Star in the constellation Cygnus
Eta Cygni
Location of η Cygni (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Cygnus
Right ascension  19h 56m 18.37184s[1]
Declination +35° 05′ 00.3224″[1]
Apparent magnitude (V) 3.889[2]
Characteristics
Evolutionary stage red clump[3]
Spectral type K0 III[4]
U−B color index +0.881[2]
B−V color index +1.035[2]
Astrometry
Radial velocity (Rv)−26.57±0.34[1] km/s
Proper motion (μ) RA: −34.165[1] mas/yr
Dec.: −28.393[1] mas/yr
Parallax (π)23.5482 ± 0.1078[1] mas
Distance138.5 ± 0.6 ly
(42.5 ± 0.2 pc)
Absolute magnitude (MV)0.74[5]
Details
Mass0.9±0.1[6] M☉
Radius10.43±0.05[7] R☉
Luminosity60[6] L☉
Surface gravity (log g)2.36±0.08[6] cgs
Temperature4,783±20[8] K
Metallicity [Fe/H]−0.02[6] dex
Rotational velocity (v sin i)2.2 [9] km/s
Other designations
Almighzal, η Cygni, 21 Cygni, BD+34 3798, HD 188947, HIP 98110, HR 7615, SAO 69116, TYC 2677-1816-1, IRAS 19544+3456[10]
Database references
SIMBADdata

Eta Cygni is a star in the northern constellation of Cygnus. It has the proper name Almighzal;[11] Eta Cygni is its Bayer designation, which is Latinized from η Cygni and abbreviated Eta Cygni or η Cyg. This star visible to the naked eye with an apparent visual magnitude of 3.889.[2] It lies along the main body of the constellation, about midway between Gamma Cygni and Albireo.[12] Based upon an annual parallax shift of 23.55 mas,[1] it is located at a distance of 138.5 light-years (42.5 pc) from the Sun.

This is an evolved red clump[3] giant star with a stellar classification of K0 III.[4] It is presently on the horizontal branch and is generating energy through the nuclear fusion of helium at its core. The star has about 0.9 times the mass of the Sun[6] and has expanded to 10 time the Sun's radius.[7] It radiates 60 times the solar luminosity from its outer atmosphere at an effective temperature of 4,780 K.[6]

Eta Cygni has five visual companions,[13] of which only component B appears to be physically associated. This magnitude 12.0 star lies at an angular separation of 7.80 arc seconds along a position angle of 206°, as of 2007.[14]

Al-Mighzal (المِغْزَل), the Wool Spindle, is an Arabic name for the "Northern Cross" of Cygnus, used in oral tradition in Saudi Arabia.[15] The IAU Working Group on Star Names adopted the name Almighzal for this star on 16 July 2026.[11]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940.  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Oja, T. (August 1986), "UBV photometry of stars whose positions are accurately known. III", Astronomy and Astrophysics Supplement Series 65 (2): 405–409, Bibcode: 1986A&AS...65..405O. 
  3. ↑ 3.0 3.1 Puzeras, E. et al. (October 2010), "High-resolution spectroscopic study of red clump stars in the Galaxy: iron-group elements", Monthly Notices of the Royal Astronomical Society 408 (2): 1225–1232, doi:10.1111/j.1365-2966.2010.17195.x, Bibcode: 2010MNRAS.408.1225P. 
  4. ↑ 4.0 4.1 Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics 11: 29–50, doi:10.1146/annurev.aa.11.090173.000333, Bibcode: 1973ARA&A..11...29M. 
  5. ↑ Cardini, D. (January 2005), "Mg II chromospheric radiative loss rates in cool active and quiet stars", Astronomy and Astrophysics 430: 303–311, doi:10.1051/0004-6361:20041440, Bibcode: 2005A&A...430..303C. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Kallinger, T. et al. (April 2019), "Stellar masses from granulation and oscillations of 23 bright red giants observed by BRITE-Constellation" (in en), Astronomy & Astrophysics 624: A35, doi:10.1051/0004-6361/201834514, ISSN 0004-6361, Bibcode: 2019A&A...624A..35K. 
  7. ↑ 7.0 7.1 Anugu, Narsireddy et al. (July 27, 2026), "Empirical H- and K-band Limb Darkening for 31 CHARA Stars: A Near-Infrared Benchmark for Stellar-Atmosphere Models", The Astronomical Journal 172 (4): 214, doi:10.3847/1538-3881/ae9878. 
  8. ↑ Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal 150 (3): 23, doi:10.1088/0004-6256/150/3/88, 88, Bibcode: 2015AJ....150...88L. 
  9. ↑ 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, doi:10.1088/0004-6256/135/1/209, Bibcode: 2008AJ....135..209M. 
  10. ↑ "eta Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=eta+Cyg. 
  11. ↑ 11.0 11.1 IAU Catalog of Star Names, International Astronomical Union, https://exopla.net/star-names/modern-iau-star-names/, retrieved 19 July 2026. 
  12. ↑ Marett-Crosby, Michael (2013), Twenty-Five Astronomical Observations That Changed the World: And How To Make Them Yourself, The Patrick Moore Practical Astronomy Series, Springer Science & Business Media, p. 231, ISBN 978-1461468004, https://books.google.com/books?id=0KRSphlvsqgC&pg=PA231. 
  13. ↑ Mason, B. D. et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal 122 (6): 3466–3471, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M. 
  14. ↑ 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  15. ↑ Al-Ajaji, Khalid; Hoffmann, Susanne M., al-Miġzal (المِغْزَل), IAU Working Group on Star Names, https://ase.exopla.net/index.php/Al-Mi%C4%A1zal, retrieved 19 July 2026. 

Coordinates: Sky map 19h 56m 18s, +35° 05′ 00″



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