Cygnus is one if the most familiar constellations in the northern hemisphere. Its name derives from the Greek word for "swan." The constellation was originally listed by the Greek astronomer Ptolemy in the 2nd century. It is shown as a long-necked bird with its wings spread wide.
The constellation Cygnus is associated with several different myths. Orpheus, the musician and poet, was said to have been transformed into a swan after his death at the hands of the Maenads and placed in the sky next to his lyre, represented by the constellation Lyra
. In another tale, Zeus transformed himself into a swan to seduce Leda, wife of King Tyndareus of Sparta, who later gave birth to Castor, Pollux, Helen (of Troy) and Clytemnestra.
The Chinese identify the constellation with Que Qiao, the "magpie bridge" that connects the lovers Niu Lang ("the cowherd") and Zhi Nu ("the weaver girl") once a year. It is said that the Goddess of Heaven found out that the two were married and separated them because Zhi Nu, a fairy, could not be with a mortal. Her husband then took their two children and went up to Heaven to be with his wife, but the Goddess would not allow this. She created a wide river in the sky with her hairpin to keep them separated. The river is the Milky Way between 
Altair and 
Vega. The story says that once a year, all the magpies in the world form a bridge so that the two can be together, and the constellation represents the celestial bridge.
The constellation Cygnus occupies an area of 804 square degrees and contains six stars with known planets. It can be seen at latitudes between +90° and -40° and is best visible at 9 p.m. during the month of September.
Cygnus contains a prominent asterism, the Northern Cross, formed by the brightest stars in the constellation. (The Southern Cross
is in the constellation Crux
The brightest star in Cygnus is 
alpha Cygni or Deneb ("the tail"), which is also the 19th brightest star in the sky. Deneb is a blue-white supergiant that marks the swan’s tail and is one of the stars of the Summer Triangle, along with 
alpha Aquilae, Altair, and 
alpha Lyrae, Vega. The triangle can be seen directly overhead at midnight during the summer in the northern hemisphere.
gamma Cygni or Sadr ("chest") lies at the centre of the Northern Cross and is surrounded by a diffuse nebula, IC I318, also known as the Gamma Cygni region. The star itself is a yellow-white supergiant.
delta Cygni, also known as Rukh in Persian or Urakhga in Akkadian is a magnitude 3 star named after the roc, a huge mythical bird of prey said to have been able to carry and eat elephants. It is a triple star approximately 170 light-years distant. Its components are a blue-white supergiant that can be spotted with the naked eye, a yellow-white companion star, and a magnitude 12 orange star.
epsilon Cygni is an orange giant that shares its traditional name, Gienah ("the wing"), with 
beta Cygni or Albireo marks the head of the swan. It is a binary star with blue and yellow components. It is only the fifth brightest star in the constellation.
Cygnus contains several interesting star clusters and nebulae. NGC 7000 or the North American Nebula got its name because of its resemblance to the continent. It is located to the east of 
Deneb. The North American Nebula is a large emission nebula, reddish in colour from the hydrogen emission line, difficult to see with the unaided eye.
IC5070 and IC5067 or the Pelican Nebula is located in an H II region, a cloud of glowing gas and plasma in which stars are formed. Lying close to 
Deneb, the nebula resembles the pelican in shape.
The Veil Nebula (NGC 6960, 6962, 6979, 6992 and 6995) is a large, ancient, relatively faint remnant of a supernova. It can be spotted south of 
epsilon Cygni, but is difficult to see without an OIII filter.
NGC 6888 or the Crescent Nebula lies between 
gamma and 
eta Cygni. It is an emission nebula created by a fast stellar wind of a Wolf-Rayet star, an evolved, massive star showing strong emission lines of helium and nitrogen or helium, carbon and oxygen. It is approximately 5,000 light-years distant.
NGC 6946 or the Fireworks Galaxy has been the site of more supernova sightings than any other galaxy. It is an intermediate spiral galaxy lying on the border between the constellations Cygnus and Cepheus
, approximately 10 million light-years away from Earth.
The Cygnus X-1 system, close to 
eta Cygni, is a well known X-ray source, the first one to be accepted as a black hole candidate. It is a binary star system that includes a blue supergiant variable and a compact object, one that cannot be classified with certainty but is small for its mass, e.g. a white dwarf, a neutron star or a black hole.
Cygnus belongs to the Hercules family of constellations, along with Hercules
, Corona Australis
, Triangulum Australe
Constellations directly bordering Cygnus are Cepheus