Sig

Its story

Sigma Cygni is a blue supergiant almost three thousand light-years away, embedded in the Cygnus OB4 association. Its atmosphere is chemically strange: abnormally rich in helium, nitrogen, calcium, cerium and europium, depleted in carbon and aluminium. Corrected for the light absorbed by interstellar dust, it shines more than fifty thousand times brighter than the Sun. Internal pulsations with a 1.59-hour period stir its spectral lines while leaving its brightness untouched.