Cygnus constellation. Cygnus, the swan, is a summer constellation in the northern hemisphere. Its brightest star is Deneb (Alpha Cygni), at middle left. This is a blue supergiant which is the 20th brightest star in the sky as seen from Earth. It is thought to be some 1500 light years from Earth. To appear this bright at such a vast distance means that it must be one of the largest and brightest stars known. The bill of the swan is represented by the star Albireo (Beta Cygni), at lower right. The constellation is also known as the Northern Cross.