The constellation of Cygnus, the Swan, dominates the richest part of the northern Milky Way in the sky overhead during the summer in the northern hemisphere. Hold your mouse cursor over the image to see constellation figures, boundaries, and star identifications. Cygnus represents a swan in several Greek myths, most notably the legend that the god Zeus disguised himself as a swan to seduce the Spartan Queen Leda, who gave birth to Polydeuces (Pollux of the Gemini Twins), Helen of Troy and Clytemnestra. Alpha Cygni is Deneb, which marks the tail of the swan. It is a spectral-class A type blue-white supergiant star that shines at magnitude 1.25. Its distance is a bit uncertain ranging from 1,400 light-years to 3,229 light-years. Beta Cygni, Albireo, marks the head of the swan. Albireo is a gold and blue double star, one of the most beautiful doubles in the night sky. Gamma Cygni is Sadr, a magnitude 2.2 spectral-class F blue-white supergiant star that is located 1,800 light-years away. Cygnus also contains the Northern Cross, an asterism comprised of the bright stars Deneb at its top, Albireo at its bottom, Sadr at its center, and Delta Cygni and Epsilon Cygni at the ends of the arms of the cross. Chi Cygni is a Mira-type pulsating variable star whose magnitude ranges from 3.3 to 14.2 over a 408 day period. 61 Cygni is known as Piazzi's Flying Star. Its large proper motion was first noted by Giuseppe Piazzi in 1804. It was the first star to have its stellar parallax measured, by Friedrich Wilhelm Bessel in 1838. 61 Cygni is a visual binary star comprised of two K-type dwarf stars with magnitudes of 5.2 and 6.05 and an apparent separation of 30 arcseconds. It is located 11.4 light-years from Earth, making it one of the closest stars to the Sun. This beautiful area is full of dust and gas and star forming regions. The large red emission nebula NGC 7000, the North America Nebula, is next to Deneb at the bottom left of the frame. Another large area of emission nebulae containing IC 1318, the Butterfly Nebula, surrounds Sadr. The large dark nebula Le Gentil 3 is in the lower left corner. NGC 6992, the brighter half of the Veil Nebula is faintly visible near the bottom center. Omicron 1 Cygni is a beautiful red, white and blue multiple star located in Cygnus. The great rift in the Milky Way, a large area of obscuring dark matter, dominates the right side of the frame in Vulpecula and extends to the Northern Coal Sack between the North America Nebula and Sadr. Cygnus was cataloged by the Greek astronomer Ptolemy in the second century C.E. (Common Era). It is the 16th largest of today's 88 modern constellations, covering 804 square degrees of sky. North is to the left in the above image.
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