Constellation Cygnus (Swan)

Cygnus: IAU Constellation Map [150]


Cygnus is a very showy and beautiful summer constellation. Its brightest stars form a figure that one can associate with the corresponding shape of the swan without much imagination. The tail of the swan sailing across the Milky Way is marked by Deneb, its head by Albireo and the two wings by delta and epsilon Cygni. Cygnus lies in a star-rich region of the Milky Way, which appears to be divided into two parts by an extensive dark cloud on dark nights. Deneb, the main star, is a corner point of the famous summer triangle, which is completed by Atair and Wega. The constellation Cygnus extends over an area of 804 square degrees in the sky and the center culminates around midnight on July 29th. [9, 15]

Stars with Proper Names [154]
α Cyg Deneb, Deneb Cygni, Deneb El Adige, Arided, Aridif, Gallina, Arrioph
β1 Cyg Albireo
γ Cyg Sadr, Sador, Sadir
ε Cyg Gienah Cygni, Gienah
π1 Cyg Azelfafage
Data for constellation Cygnus [150]
IAU NameCygnus
IAU GenitiveCygni
IAU Abbr.Cyg
English NameSwan
Opposition29 July
Season (47° N)March … December
Right Ascension19h 07m 30s … 22h 03m 03s
Declination+27° 43' 57" … +61° 21' 28"
Area804 deg2
Neighbours (N↻)Cep, Dra, Lyr, Vul, Peg, Lac

Deep-Sky Object Descriptions


Cygnus: Constellation Cygnus with red emission nebulae, Cirrus nebulae and summer Milky Way; Sigma 50 mm f/1.4 DG HSM Art at f/2.8; Canon EOS 6Da; iOptron SkyGuider Pro; 99x1 min @ 800 ASA; Bern, Elfenau, 561 m AMSL; © 10. 7. 2015 Manuel Jung [45]
Cygnus: Milky Way with dark clouds and bright nebulae; Nikon D3, Nikkor 24-70mm 2.8G @ f/4, SkyWatcher StarAdventurer Pro; L: 50*120s, D: 15*120s, F: 15, ISO 1600; Glaubenberg Pass; © 18. 9. 2020 Bernd Nies [36]

Mythology and History

In Greek mythology, Cyknos (Cygnus) was a musician king and a devoted friend of Phaethon, the son of the sun god Helios. One day Phaethon persuaded his father to let him lead the sun chariot across the sky, but then he lost control of the horses and wreaked havoc on heaven and earth. The king of the gods, Zeus, hurled one of his thunderbolts at Phaethon, killing him instantly. His still smoldering body fell into the river Eridanus. Kyknos jumped into the river, swam back and forth and kept diving to find his friend's body. It was said that it looked like a swan swimming in the water, diving for food. Helios looked on sadly and picked up his son's loyal friend and sat him on a place between the stars in the firmament. [71]

Constellation Cygnus
Constellation Cygnus: Illustration from «Uranometria» by Johann Bayer, copper engraving by Alexander Mair, 1603 [28]

In another version of this myth, Cygnus wandered in a poplar grove on the bank of the Eridanus River, mourning the death of his friend. In the end, the gods pitied him so much that they turned him into a swan of stars. Since then it has been said that swans sang sad songs when they are about to die. This is the origin of the expression "swan song", which denotes the last work of a musician or poet before his death. [71]

At another time and place in Greek mythology, Zeus slipped into the shape of a swan in order to be able to approach Leda, the wife of King Tyndareus of Sparta, who was bathing her lovely body in the river. The immortal children of Leda, who had Zeus for their father, were Helena and Pollux. The mortal children she bore to her husband Tyndareus were Castor and Clytemnestra. [7, 20]

In Arabia, the constellation has been seen as a flying bird. In Christian symbolism it was interpreted as the crux of Christ, the cross on Calvary and the northern cross. [20, 54]


  • [7] «Der grosse Kosmos-Himmelsführer» von Ian Ridpath und Wil Tirion; Kosmos Verlag; ISBN 3-440-05787-9
  • [9] «Drehbare Sternkarte SIRIUS» von H. Suter-Haug; Hallwag-Verlag, Bern
  • [15] «Hartung's Astronomical Objects for Southern Telescopes» by David Malin and David J. Frew; Melbourne University Press 1995; ISBN 0-522-84553-3
  • [20] «Sternbilder und ihre Mythen» von Gerhard Fasching; Zweite, verbesserte Auflage; Springer Verlag Wien, New York; ISBN 3-211-82552-5 (Wien); ISBN 0-387-82552-5 (New York)
  • [28] «Uranometria omnium asterismorum continens schemata, nova methodo delineata aereis laminis expressa» Johann Bayer, Augsburg, 1603; DOI:10.3931/e-rara-309
  • [36] Fotogalerie Bernd Nies;
  • [45] Astro-, Landschafts- und Reisefotografie sowie Teleskopbau, Manuel Jung;
  • [54] Eye On The Sky: Cygnus by Deborah Byrd; Astronomy 8/92, p.48
  • [71] The Starry Sky: Cygnus by Deborah Byrd; Astronomy 7/94, p.52
  • [150] IAU: The Constellations, 11. Oktober 2020;
  • [154] Yale Bright Star Catalog, 15. Oktober 2020;