Observing the Constellation Cygnus

Constellation Cygnus Facts

The Constellation of Cygnus the Swan is an important summer target because it lies along the Milky Way and holds many deep-sky treasures.

The constellation Cygnus the Swan has many important observing targets and is easy to find in the night sky. The mythology of Cygnus tells the story of Zeus who changed into the form of a swan to entice Queen Leda. From this union were born the twin’s Castor and Pollux, which can be found in the constellation Gemini. Find Cygnus high above the eastern horizon after sunset in summer.

Stars

The constellation forms a lower case “t” shape, with additional stars off the sides to show a bend for the wings. Cygnus is sometimes called the Northern Cross because of this shape. The bottom of the cross is the same as the head of the swan. The star marking this point is known as Albireo, and is largely regarded as the most beautiful double star in the heavens. A larger yellow star and smaller blue star are easily divided in a small telescope. The brighter star of Albireo (or Beta Cygni) is magnitude 3.1, and the dimmer is magnitude 5.1. The stars are approximately 380 light-years distant.

At the other end of the constellation, marking the tail of the swan or the top of the cross is Deneb. The brightest star in Cygnus, at magnitude 1.3, it also marks one of the corners in the Summer Triangle. The other two points are Altair in Aquila and Vega in Lyra. Deneb is a blue-white supergiant star lying 3,000 light-years away, which is a long-distance for a star that shines so brightly in our skies.

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Omicron Cygni, or 30 and 31 Cygni, is a double star with orange and blue components that can be seen with binoculars. These stars can be found between Deneb and Delta Cygni, which is the western star in the cross shape. At magnitudes 3.8 and 4.8, 30 and 31 Cygni lie 1300 and 700 light-years away, respectively.

Clusters and Nebulae

Lying less than two degrees from Sadr, or Gamma Cygni, the 2.23-magnitude star at the center of the cross, is M29. M29 is a 6.6-magnitude open cluster. The other Messier object in Cygnus is M39, an open cluster lying about 9 degrees northeast of Deneb. M39 is magnitude 4.5: try to catch it without binoculars. Back at Sadr, a 7.4-magnitude open cluster, NGC 6910, lies just a half degree from the star to the north. Scanning along the western boundary of Cygnus will reveal other clusters, including the magnitude 7.3 Foxhead Nebula (NGC 6819) and the 6.8-magnitude Hole-in-a-Cluster (NGC 6811).

Also on the western side of the constellation, five and a half degrees north of Gamma, is the Blinking Planetary, NGC 6826. As you move your eyes across it, does it appear to blink?

A little over three degrees east of Deneb is NGC 7000, the North America Nebula, so named because it has a similar shape. This large nebula is seen in many photos, but you can glimpse it under dark skies with binoculars because of its large shape, extending up to four moon-widths. Another nebula to see with binoculars is the Veil Nebula, NGC 6992. The Veil Nebula spans a big sweep of sky just south of Epsilon Cygni, the eastern star in the cross’s arm. This entire region is called the Cygnus Loop and is the remains of a star that exploded in a supernova 5,000 years ago.

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Because of the rich Milky Way background in this part of the sky, there are many more nebulas and clusters to be found if you are patient and sweep with binoculars or a telescope.

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