Chi Cygni

χ Cygni
Location of χ Cygni (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 50m 33.92439s[1]
Declination +32° 54′ 50.6097″[1]
Apparent magnitude (V) 3.3 – 14.2[2]
Characteristics
Spectral type S6+/1e = MS6+[3] (S6,2e – S10,4e[4])
U−B color index −0.30 – +0.98[5]
B−V color index +1.56 – +2.05[5]
Variable type Mira[2]
Astrometry
Radial velocity (Rv)+1.60[6] km/s
Proper motion (μ) RA: -20.16[1] mas/yr
Dec.: -38.34[1] mas/yr
Parallax (π)5.53 ± 1.10 mas[1]
Distance553 ly
(169[7] pc)
Absolute magnitude (MV)−3.2 – +7.7[8]
Details
Mass2.1+1.5
−0.7[7] M☉
Radius348 – 480[7] R☉
Luminosity6,000 – 9,000[7] L☉
Surface gravity (log g)0.49[9] cgs
Temperature2,441 – 2,742[7] K
Metallicity [Fe/H]-1.00[9] dex
Other designations
χ Cyg, Chi Cyg, HD 187796, BD+32°3593, HIP 97629, HR 7564, SAO 68943
Database references
SIMBADdata

Chi Cygni (Latinised from χ Cygni) is a Mira variable star in the constellation Cygnus, and also an S-type star. It is around 500 light years away.

χ Cygni is an asymptotic giant branch star, a very cool and luminous red giant nearing the end of its life. It was discovered to be a variable star in 1686 and its apparent visual magnitude varies from as bright as 3.3 to as dim as 14.2, corresponding to a brightness factor of over 20,000. It is only visible to the naked eye for a short period near each maximum.

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