Eta Cygni
Star in the constellation Cygnus
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Eta Cygni (η Cygni), also named Almighzal,[11] is a star in the northern constellation of Cygnus. It is visible to the naked eye with an apparent visual magnitude of 3.889.[2] The star 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 138.5 light years from the Sun.
 | |
| Observation data Epoch J2000.0 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 mas/yr[1] Dec.: −28.393 mas/yr[1] |
| Parallax (π) | 23.5482±0.1078 mas[1] |
| Distance | 138.5 ± 0.6 ly (42.5 ± 0.2 pc) |
| Absolute magnitude (MV) | 0.74[5] |
| Details | |
| Mass | 0.9±0.1[6] M☉ |
| Radius | 10.43±0.05[7] R☉ |
| Luminosity | 60[6] L☉ |
| Surface gravity (log g) | 2.36±0.08[6] cgs |
| Temperature | 4,783±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 | |
| SIMBAD | data |
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]