Cygnus

Large prominent constellation of the northern hemisphere, represented as a swan. Its brightest star is first-magnitude Alpha Cygni or Deneb.

Beta Cygni (Albireo) is a yellow and blue double star, visible through small telescopes. The constellation contains the North America nebula (named after its shape), the Veil nebula (the remains of a supernova that exploded about 50,000 years ago), Cygnus A (apparently a double galaxy, a powerful radio source, and the first radio star to be discovered), and the X-ray source Cygnus X-1, thought to mark the position of a black hole. The area is rich in high-luminosity objects, nebulae, and clouds of obscuring matter. Deneb marks the tail of the swan, which is depicted as flying along the Milky Way. Some of the brighter stars form the Northern Cross, the upright being defined by Alpha, Gamma, Eta, and Beta, and the crosspiece by Delta, Gamma, and Epsilon Cygni.

One of the fainter stars, 61 Cygni, has an exceptionally large proper motion and was therefore chosen by Bessel for his first determination of a stellar distance. In 1838 he found it to be only 10.4 light years from the Sun.