Chi Cygni

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

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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