W Cygni
W Cygni is a semi-regular variable star in the constellation Cygnus, about 570 light-years from Earth. It can sometimes be seen with the naked eye but doesn’t have a Bayer designation. It may be part of a binary system with a hotter companion, but this isn’t confirmed. It was identified as a variable by John Ellard Gore in 1885.
The star’s brightness varies from magnitude 5.10 at its brightest to 6.83 at its faintest. Its main cycle is about 131.7 days, though other periods around 131 and 234 days occur. The changes are thought to come from pulsations in the star’s outer layers, likely in the first overtone, with possible very slow variations over 3,000–5,000 days.
W Cygni is an aging red giant on the asymptotic giant branch. Its spectrum ranges from M4e to M6e, with possible Technetium in the spectrum. Its mass is similar to the Sun’s, but it has expanded to about 227 times the Sun’s radius and shines about 5,888 times brighter. Its surface temperature is about 3,373 K.
Distance: about 570 light-years. Absolute magnitude: around -0.43.
Other names include W Cyg, BD+44°3877, HD 205730, HIP 106642, and HR 8262.
This page was last edited on 3 February 2026, at 20:34 (CET).