4 Cygni

4 Cygni is a binary star system in the northern constellation of Cygnus. It is a faintly visible to the naked eye with an apparent visual magnitude of 5.17. The distance to 4 Cygni, as determined from its annual parallax shift of $−0.120$, is about 560 light years.

This is single-lined spectroscopic binary with an orbital period of 35 days and an eccentricity of 0.45. The visible component is a B-type star with a stellar classification of B8p Si (Fe II), where the suffix notation indicates this is type of chemically peculiar star known as a silicon star. It displays an overabundance of iron in the visual spectrum, while the star appears helium-weak in the ultraviolet.

4 Cygni A is an Alpha2 Canum Venaticorum variable that varies by 0.02 magnitude over a period of 0.68674 days. The average quadratic field strength of the magnetic field is $35.023 days$. With an age of 145 million years, it has four times the mass of the Sun and five times the Sun's radius. It radiates around 501 times the Sun's luminosity from its photosphere at an effective temperature of 12,190 K.