Y Cygni is an eclipsing and double-lined spectroscopic binary star system in the constellation of Cygnus. It is located about 4,900 light-years from Earth. The system was one of the first binaries with a convincing detection of the apsidal precession.[4]
The two stars, being O-type main-sequence stars, orbit each other with a period of nearly 3 days.[4]
The early type of Y Cyg made it a popular target for astronomers in the past, and spectroscopic orbits have been historically computed numerous times.[5] The first of these studies was published in 1920 by John Stanley Plaskett.[6] Extensive spectroscopic studies of Y Cyg were carried out as early as 1930.[7] Several follow-ups to these have been published in 1959,[8] 1971,[9][10] and 1980.[11] The latter of these contained an estimate of the period of apsidal precession.
