Cygnus the Swan flies the Milky Way
Cygnus the Swan is a constellation that helps you find the Milky Way on summer evenings. Its brightest star, Deneb, marks one of the corners of the Summer Triangle. Cygnus is also home to the most beautiful double star in the sky, Albireo.
The mythology of Cygnus tells the story of Zeus, who changed into the form of a swan to entice Queen Leda. From this union came the twins Castor and Pollux, the bright stars of the constellation Gemini.
How to find Cygnus the Swan
You can find Cygnus high above the eastern horizon after sunset in summer. As the sky grows dark, the first of its stars that you’ll see is Deneb, the brightest in the constellation at magnitude 1.3. Deneb is the tail feather of the Swan, or the top of the lowercase “t” shape. Cygnus also has the nickname of the Northern Cross.
As the night wears on, you’ll be able to trace out the body of the Swan and its bent wings, then find the double star, Albireo, which marks its head.
If you can find the large Summer Triangle shape, Deneb in Cygnus is the star that lies toward the northeast.
Once you’ve found Cygnus, you just need to look along its length to find the hazy cloud behind it that is our galaxy, the Milky Way. The Milky Way runs along the same axis as the long line of the lowercase t or the body of the Swan.
Stars of the Swan
Deneb, or Alpha Cygni, is the 19th brightest star in the sky. At magnitude 1.3, it’s a blue-white supergiant star lying about 2,600 light-years away, which is a long distance for a star that shines so brightly in our skies.
Albireo, the head of the Swan, is largely regarded as the most beautiful double star in the heavens. You can easily divide Albireo into a larger yellow star and smaller blue star 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.
Omicron Cygni, or 30 and 31 Cygni, is a double star with orange and blue components that you can see with binoculars. These stars lie between Deneb and Delta Cygni, which is the western wing of the Swan. At magnitudes 3.8 and 4.8, 30 and 31 Cygni lie 1,300 and 700 light-years away, respectively.
Deep-sky objects in Cygnus
You can find an open cluster in Cygnus lying less than two degrees from Sadr, or Gamma Cygni, the magnitude 2.23 star at the center of the cross or Swan. This open cluster is M29, at magnitude 7.1. Try using binoculars to track it down.
One other Messier object in Cygnus is M39, an open cluster lying about nine degrees northeast of Deneb. M39 is magnitude 4.5. This one you can try to spot with just your eyes alone.
Now head back to Sadr. A 7.4-magnitude open cluster, NGC 6910, lies just a 1/2 degree north of the star. Scanning along the western boundary of Cygnus with binoculars or a telescope reveals 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, 5 1/2 degrees north of Gamma, is the Blinking Planetary, NGC 6826. As you move your eyes across it, does it appear to blink?
North America and Veil nebulae
There are two somewhat famous nebulae in Cygnus: the North America Nebula and the Veil Nebula.
The North America Nebula, or NGC 7000, lies a little over three degrees east of Deneb. When you look at it in photos, can you trace out the shape of the continent for which it’s named? You can glimpse this large nebula under dark skies with binoculars. It extends up to four moon-widths.
You can also use binoculars to see the Veil Nebula, or NGC 6992. The Veil Nebula spans a big sweep of sky just south of Epsilon Cygni, the eastern star in the Swan’s wing. This entire region is the Cygnus Loop and consists of the remains of a star that exploded in a supernova 5,000 years ago.
Because of the rich Milky Way background in this part of the sky, you can find many more nebulae and clusters if you’re patient and sweep with binoculars or a telescope.
Bottom line: Cygnus the Swan is a constellation that lies atop the Milky Way. Its brightest star, Deneb, is part of the Summer Triangle.