is the brightest star in the constellation of Cygnus, the swan. It is one of the vertices of the asterism known as the Summer Triangle and forms the 'head' of the Northern Cross. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous stars. However, its exact distance (and hence luminosity) has been difficult to calculate; it is estimated to be somewhere between 55,000 and 196,000 times as luminous as the Sun, rivalling Rigel as the most inherently luminous star of first magnitude.