Astronomical Lore

Constellation Cygnus

Constellation Cygnus

The constellation we call Cygnus (the Swan) was identified as a separate constellation from ancient times. It was often identified as a bird, generally a duck or hen. It was probably Urakhga to the Sumerians. Certainly that constellation was a stellar bird of some kind. The Babylonians called it the Bird of the Forest. In the Egyptian zodiac (Denderah), it was called Tes-ark (This from Afar). The Greeks called it Ornis (the Bird). The Romans were the first to identify it as a swan. They named it Cygnus (the Swan) and adopted a Greek myth to explain its name. The Arabs called it Rukh (the Hen), a name derived from its ancient Sumerian name. This name passed into legend as Roc, the bird encountered by Sinbad the Sailor. The Christians of northern Europe called it the Northern Cross, because its five brightest stars form a Latin cross, and associated it with the Cross of Calvary.

Modern drawings show Cygnus as a swan in flight down the path of the Milky Way. Older drawings show a swan springing from the ground.

Cygnus reaches its highest point in the evening sky in September. The constellation is located southeast of Draco and northwest of Pegasus, next to the constellations Cepheus and Lyra. This region of the Milky Way is remarkable for having an unusual number of deeply colored red and orange stars. From this peculiarity, it has been called the Red Region of Cygnus.

Constellation Cygnus

Cygnus contains 81 stars and is quite bright, with stars generally of the third and fourth magnitude. It contains five double stars and one quadruple star. The stars include:

  • Alpha Cygni (α Cyg), known as Deneb, from the Arabic ذنب الدجاجة (ðanab ad-dajāja, Hen’s Tail). This star marks the tail of the swan. It is a super giant (more than a hundred times the diameter of the Sun) with a very high luminosity. Because it is so far away (3,200 light years) its real brilliance is lost in space. Deneb forms the Summer Triangle with Vega and Altair.
  • Beta Cygni (β Cyg), called Albireo, from a 16th century edition of Ptolemy’s Almagest, which called it ab ireo, the meaning of which is unknown. The Arabs called it منقار الدجاجة (minqār ad-dajāja, Hen’s Beak).
  • Gamma Cygni (γ Cyg), called Sadr, from the Arabic لصدر الدجاجة (aş-şadr ad-dajājah, Hen’s Breast). Between Gamma and Beta Cygni is the Cygnus Star Cloud, a vast region of exceptional beauty.
  • Epsilon Cygni (ε Cyg), called Gienah, from the Arabic جناح (janāħ, Wing).
  • Two stars in the tail are named Azel (The One Who Goes and Returns) and Fafage (Gloriously Shining Forth).
  • Cygnus X-1, an x-ray source, thought to be a black hole.

For more, see Constellations of Words.