Tuesday 19 September 2017 - 08:29:36 Posted by  Bobby

 Mythology of Cygnus

Cygnus is a large constellation that depicts the swan into which, according to Greek myth, the god Zeus transformed himself for one of his illicit love trysts. One story says that the objects of his desire was Queen Leda of Sparta, and that their union produced either one or two eggs, from which hatched the twins Castor and Pollux, as well as Helen of Troy. The swan's beak is marked by Beta Cygni and its tail by Alpha Cygni, named Deneb (from an Arabic word meaning "tail"). Deneb forms one corner of the Summer Triangle, with Vega (in Lyra) and Altair (Aquila) marking the other two. Since it is also identifiable by its cross-shape, Cygnus is sometimes called the Northern Cross. It lies in a rich part of the Milky Way.

 The Facts

  • Depiction: The Northern Cross
  • Pronounced: SIG-nus
  • Genitive: Cygni
  • Abbreviation: Cyg
  • Highest in the Sky: August to September
  • Size Ranking: 16th
  • Coverage Area: 804 Sq. Degrees
  • Right Acension: 21 hours
  • Declination: 40°
  • Visibility: 90°N to 32°S

 Notable Objects

  • Alpha Cygni (Deneb): Blue-white super giant star
  • Beta Cygni (Albireo): Double star
  • Omicron-1 Cygni (31 Cygni): Orange giant star
  • Chi Cygni: Variable red giant star
  • 61 Cygni: Double star
  • M39: Open cluster
  • NGC 6826 (The Blinking Planetary): Planetary Nebula
  • NGC 6992 (The Veil Nebula): Dark nebula
  • NGC 7000 (The North American Nebula): Dark nebula
  • Cygnus A: Galaxy
  • Cygnus X-1: Black hole

 Named Stars

  • Deneb, Alpha Cygni
  • Albiero, Beta Cygni
  • Sadir, Gamma Cygni
  • Gienah, Epsilon Cygni
  • Ruchba, Omega Cygni

 Best Viewed Objects/Stars

Alpha Cygni (Deneb)

 The brightest star in Cygnus, at magnitude 1.3. It is a luminous blue-white supergiant lying more than 3,000 light-years away, which makes it the most distant of all first-magnitude stars.

Beta Cygni (Albireo)

 A beautiful double star. The two stars, magnitudes 3.1 and 5.1, can be divided with powerful binoculars. They are easy to separate with a telescope, through which they present a striking contrast of orange and blue-green. Both stars lie about 380 light-years away, but it is not known whether they form a true binary.

Omicron-1 Cygni (31 Cygni)

 An orange-colored giant, magnitude 3.8, which has a wide 5th-magnitude, bluish companion (30 Cygni), ideal for binocular observation. A closer bluish star of 7th magnitude is also visible with binoculars or a small telescope.

Chi Cygni

 A pulsating red giant, one of the Mira class of variable stars, that ranges in brightness between 3rd and 14th magnitudes every 13 months or so.

61 Cygni

 An attractive double star. The two components, of magnitudes 5.2 and 6.1, can be seen separately through a small telescope or even powerful binoculars. Both are orange dwarfs, smaller and fainter than the Sun, and are easily visible only because they are relatively close to us, 11.4 light-years away. They orbit each other every 680 years.


 An open cluster, just visible to the naked eye under good conditions. Binoculars or a small telescope show its brightest stars. It covers the same area of sky as the full moon, and lies about 1,000 light-years away.

NGC 6826 (The Blinking Planetary)

 A planetary nebula visible with a small telescope as a bluish disk of similar size to the disk of Jupiter. Looking alternately at it and to one side gives the impression that it is blinking on and off, which explains its popular name.

NGC 6992 (The Veil Nebula)

 Part of a large, complex nebula called the cygnus loop which is the remains of a star that exploded as a supernova perhaps 5,000 years ago. In clear skies, the Veil Nebula section can be seen with binoculars or a small telescope, but the whole nebula is best seen on photographs.

NGC 7000 (The North American Nebula)

 A large nebula, visible under dark skies with binoculars or a wide-field telescope, extending for up to four Moon diameters. It is best seen on long-exposure photographs, where it takes the shape of the continent North America, hence its popular name.

Cygnus A

 A peculiar galaxy, thought to be two distant galaxies in collision. A large telescope is needed to see it, as it is of 15th magnitude. It is also a strong radio source.

Cygnus X-1

 A possible black hole, and one of the strongest X-ray sources in the sky. It appears optically as a 9th-magnitude blue supergiant, about 8,000 light-years away. The X rays come from an invisible companion, which orbits the supergiant every 5.6 days. This companion is the supposed black hole.


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