Cygnus (from the Latin word Cygni, meaning "swan") is a northern constellation. It was one of Ptolemy's 48 constellations, and is also one of the 88 modern constellations. Because of the pattern of its main stars, it is sometimes known as the Northern Cross (in contrast to the Southern Cross).
The bird extends over the summer Milky Way, appearing to fly south.
Notable features
Cygnus contains several bright stars.
Deneb, α Cygni, is an extremely brilliant star, very prominent despite its distance (1 800 light years). The blue supergiant forms the swan's tail, the upper end of the Northern Cross, and one of the vertices of the so-called "Summer Triangle".
Albireo, β Cygni, is at the swan's beak. It is one of the most beautiful double stars of the sky, a golden star easily distinguishable in a small telescope from its blue companion.
Another interesting star is 61 Cygni. This star has one of the highest proper motions of any star in the sky (except the Sun) and was accordingly one of the first to have its distance measured. It is 11.4 light years, one of the closest stars to our solar system.
The star 16 Cygni B is an extrasolar planetary system with one confirmed planet 1.5 times the mass of Jupiter.
Cygnus also contains the X-ray source Cygnus X-1, which is considered to be one of the most likely black hole candidates.
In addition, Cygnus has a variety of variable stars, including XX Cyg and V508 Cyg.
Several star clusters and nebulae are found in Cygnus due to its position on the Milky Way. NGC 7000, the North America Nebula, is found a bit to the east of Deneb. Its resemblance to the continent is best appreciated in photographs.
History and mythology
The constellation bears a resemblence to a wide winged, long necked, bird, in graceful flight [1]. In Greek mythology, the constellation represents several different legendary swans. Zeus disguised himself as a swan to rape Leda, who gave birth to the Gemini, Helen of Troy, and Clytemnestra.
Orpheus was transformed into a swan after his murder, and was said to have been placed in the sky next to his lyre.
Finally, it is said that a youth named Cygnus was the boyfriend of the ill-fated Phaethon. After Phaethon was killed trying to drive the chariot of the sun, Cygnus searched desperately for his body in the river Eridanus where it had fallen. He dove so many times into the river that Zeus took pity on him and changed him into the waterbird that has since borne his name.
Cygnus, together with other constellations in the Zodiac sign of Sagittarius (specifically, Lyra, and Aquila, together with Sagittarius itself), may be a significant part of the origin of the myth of the Stymphalian Birds, one of The Twelve Labours of Herakles.
In Chinese mythology, the constellation Cygnus is the site of the once-a-year magpie bridge which connects the lovers Niu Lang and Zhi Nu (see Qi Xi).