[4] KY Cygni is heavily reddened due to interstellar extinction, losing an estimated 7.75 magnitudes at visual wavelengths.

[7] KY Cygni is classified as a luminous red supergiant with a strong stellar wind.

[2][12] Its properties are uncertain, but the temperature is around 3,500 K. A model fit based on K-band infrared brightness gives a luminosity of 273,000 L☉, corresponding to a radius of 1,420 R☉.

Another model based on visual brightness gives an unexpectedly large luminosity of 1,107,000 L☉, with the difference due mainly to the assumptions about the level of extinction.

[7] More recently, integration of the spectral energy distributions across a full range of wavelengths from U band to the 60 micron microwave flux gives an even lower luminosity of 138,000 L☉,[2] and a 2020 paper published a luminosity of 150,000 L☉, which give a smaller radius of 1,032 R☉ using an effective temperature of 3,535 K.[8] KY Cygni is a variable star with a large amplitude but no clear periodicity.