Kappa Cygni
Star in the constellation Cygnus
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Kappa Cygni, Latinized from κ Cygni, is a star in the northern constellation of Cygnus. It has an apparent visual magnitude of 3.8,[2] which is bright enough to be seen with the naked eye. In the constellation, it forms the tip of Cygnus's left wing.[8] The radiant of the minor Kappa Cygnids meteor shower is located about 5° north of this star.[9]
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 17m 06.16865s[1] |
| Declination | +53° 22′ 06.4534″[1] |
| Apparent magnitude (V) | 3.814[2] |
| Characteristics | |
| Evolutionary stage | horizontal branch[3][4] |
| Spectral type | G9 III[5] |
| U−B color index | +0.767[2] |
| B−V color index | +0.965[2] |
| Astrometry | |
| Radial velocity (Rv) | −29.36±0.09[6] km/s |
| Proper motion (μ) | RA: +60.07[1] mas/yr Dec.: +122.83[1] mas/yr |
| Parallax (π) | 26.27±0.10 mas[1] |
| Distance | 124.2 ± 0.5 ly (38.1 ± 0.1 pc) |
| Absolute magnitude (MV) | +0.84[6] |
| Details[7] | |
| Mass | 2.19+0.14 −0.07 M☉ |
| Radius | 8.65±0.10 R☉ |
| Luminosity | 44.5±1.4 L☉ |
| Surface gravity (log g) | 2.878+0.007 −0.004 cgs |
| Temperature | 5,066+50 −47 K |
| Metallicity [Fe/H] | +0.06+0.10 −0.13 dex |
| Rotational velocity (v sin i) | 1.08±0.28[6] km/s |
| Age | 0.88+0.11 −0.15 Gyr |
| Other designations | |
| κ Cyg, 1 Cygni, BD+53°2216, FK5 726, HD 181276, HIP 94779, HR 7328, SAO 31537 | |
| Database references | |
| SIMBAD | data |
Kappa Cygni has been reported to vary in brightness between magnitudes 3.76 and 3.82, but this has not been confirmed and it is not formally catalogued as a variable star. It is tentatively classified as a type SRd semiregular variable star with a possible period around 79 days.[10] Hipparcos photometry indicated variability, but only by about 0.01 to 0.02 magnitudes which is potentially within the margin of error for a constant star.[11] TESS data at two-minute intervals over a two-year period indicates variability of only 90 parts per million, but with a possible period of 0.9 days.[12]
Examination of this star's spectrum show it to match a stellar classification of G9 III,[5] with the 'III' luminosity class revealing that it has consumed the hydrogen fuel at its core and expanded into the giant star stage of its stellar evolution. Despite being younger than the Sun with an age of 880 million years, it has reached its current evolutionary stage because more massive stars evolve faster. Kappa Cygni has expanded to 8.65 times the Sun's radius and is glowing with 44.5 times the Sun's luminosity. The outer envelope has an effective temperature of 5,066 K,[7] giving it the yellow-orange hue of a star near the transition from a G- to a K-type classification.[13]