Cygnus, The Swan, is one of the more obvious constellations in the summer skies, which -- because of its shape -- is sometimes called the Northern Cross. Alpha Cygni is known as Deneb, from Al Dhanab al Dajajah (the Hen's Tail). It marks the tail of the swan. This is a supergiant (more than a hundred times the diameter of the Sun) with a very high luminosity. Since it is so far away (3200 light years) its real brilliance is lost in space.

In Star Trek, the Deneb system was an inhabited star system in Federation space. In the very first episode of Star Trek: The Next Generation, "Encounter at Farpoint", the USS Enterprise-D visited the system to investigate the construction of the first Farpoint Station, only to discover that the station was in fact a spaceborne entity enslaved by the Bandi. In the episode "Sarek", Alpha Cygnus IX is the planet where the Treaty of Alpha Cygnus IX, negotiated by Ambassador Sarek, was signed. Deneb is also encountered in the original series of Star Trek. In the episode "Where No Man Has Gone Before", many of the inhabitants of Deneb could communicate telepathically.

In reality, Alpha Cygni is the prototype for a variable class of pulsating supergiants. These variables have a spectral type of A or B and very high absolute magnitudes. Deneb's mass is estimated at 20 to 25 solar masses. As a white supergiant, its high mass and temperature mean that the star will have a short lifespan and will probably become a supernova within a few million years. It has already stopped fusing hydrogen in its core.