59 Cygni

59 Cygni (also designated HD 200118) is a rapidly rotating Be star located in the constellation Cygnus. It is a variable star, classified as a Gamma Cassiopeiae variable, exhibiting irregular changes in brightness due to mass ejections and circumstellar disk variations. 59 Cygni is a bright star, visible to the naked eye under favorable viewing conditions.

The star's spectral classification is B1.5Ve, indicating a B-type star with emission lines in its spectrum, characteristic of a Be star. The "e" suffix signifies the presence of emission lines, which are produced by a hot, tenuous gas disk surrounding the star's equator. This disk is formed by material ejected from the star's rapidly rotating surface.

59 Cygni is known for its complex and variable circumstellar disk. The disk's density and structure change over time, leading to variations in the star's brightness and spectral characteristics. Observations have revealed episodic mass-loss events from the star, contributing to the disk's evolution.

The distance to 59 Cygni is estimated to be around 800 to 900 light-years based on parallax measurements. Its high luminosity and rapid rotation rate are typical characteristics of Be stars.