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A prominent and one of the most familiar constellations of the northern hemisphere, Cygnus is among the most recognizable and brightest constellations in the night sky. It derives its name from the Latin word ‘swan’ and is represented as a long–necked bird with its wings spread wide. The Greek astronomer Ptolemy listed this constellation in the 2nd century. Although it is a prominent constellation in the northern sky, it flies southward along the Milky Way and into the Summer Triangle. It belongs to the Hercules family of constellations and can be best visible in the month of September at 9 pm. Let us further discuss this constellation in detail.

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Which stars comprise the constellation?

Some notable stars of this Constellation are:

ASTERISM–Northern Cross: The five stars which form the Northern Cross are Deneb (Alpha Cygni), Albireo (Beta Cygni), Delta Cygni, Gienah (Epsilon Cygni) and Sadr (Gamma Cygni) at the centre.

Deneb (Alpha Cygni): Deneb is the brightest star in Cygnus and the 19^th brightest star in the night sky. It is basically a blue–white supergiant with a visual magnitude of 1.23. It is about 60,000 times brighter than the sun. Deneb is also one of the large white stars known.
Sadr (Gamma Cygni): Sadr is a star located at the intersection of the Northern Cross. It is about 1,800 light years away from the earth. Sadr, with a visual magnitude of 2.23 is one of the brightest stars visible in the night sky. It is believed that Sadr is about 12 million years old.
Gienah (Epsilon Cygni): It is basically an orange giant star in this constellation. With a visual magnitude of 2.480, it is about 72.7 light years away. Gienah is about 62 times brighter than the Sun.
Rukh (Delta Cygni): Rukh is a triple star in this constellation. It has a combined magnitude of about 2.87 and is about 165 light years away. Its closest companion is a yellow–white star with a magnitude of 6.33. The brightest component in this star system is basically a blue–white giant whereas the third component is a 12^th magnitude orange giant.
Albireo (Beta Cygni): Albireo is the fifth brightest star in this constellation. It is basically a binary star system, which appears as a single third magnitude star to the naked eye. Albireo is about 380 light years away. It comprises of a yellow star with a magnitude of 3.18 and a fainter blue companion star with a magnitude of about 5.82.
Z Cygni (Zeta Cygni): It is a yellow star in this constellation which is about 151 light years away. Zeta Cygni has a visual magnitude of 3.20 and is about 119 times brighter than the sun. It also comprises of the 12^th magnitude companion, which is believed to be a white dwarf.
t Cygni (Tau Cygni): It is basically a double star in this constellation comprising of a yellowish white sub giant, a sixth magnitude companion and a yellow main sequence star. Its components have a magnitude of 3.84 and 6.44. Tau Cygni is about 68.2 light years away from the solar system.
k Cygni (Kappa Cygni): It is basically a giant star in this constellation. With a visual magnitude of 3.814, it is about 124.2 light years away from the earth. Kappa Cygni is renowned for its meteor shower associated with it. The meteor shower occurs in the month of August every year.
n Cygni (Eta Cygni): It is an orange giant with a visual magnitude of 3.909 and is about 139 light years away.
π Cygni (Pi Cygni): Pi Cygni comprises of two star systems. Pi–1 has a visual magnitude of 4.67 and is about 1680 light years away whereas Pi–2 has a visual magnitude of 4.23 and is about 1156 light years away.
Bessel’s Star (Piazzi’s Falling Star): It is basically a double star in this Cygnus comprising of a pair of two dwarfs, which orbit each other for a period of 659 years. These two dwarfs have a visual magnitude of 5.21 and 6.03. It is about 11.41 light years away and is also the 15^th nearest known system to the earth.

The other notable stars in this constellation are 34 Cygni (P Cygni), 39 Cygni, 0 Cygni (Theta Cygni), 16 Cygni, Gliese 777 and Ruchba (Omega Cygni).

Does it contain any deep sky objects and galaxies?

There are a few deep sky objects in the constellation. They include:

Messier 29 (NGC 6913): Messier 29 is an open cluster in this constellation. It has a visual magnitude of about 7.1 and is about 4,000 light years away. Under good conditions, it can be seen with binoculars. The estimated age of Messier 29 is believed to be 10 million years. The brightest star in this cluster has a visual magnitude of 8.59.
Messier 39 (NGC 7092): It is an open cluster in this constellation. It has a visual magnitude of 5.5 and the estimated age of Messier 39 is believed to be about 200 to 300 million years old. The brightest star in this cluster has a visual magnitude of 6.83. The cluster is about 800 light years away from the solar system. In this cluster, all the stars observed are on the main sequence.
Fireworks Galaxy (Caldwell 12): It is basically an intermediate galaxy in Cygnus. With a visual magnitude of 9.6, it is about 22.5 million light years away.
Cygnus X-1: It is a well known X–ray source and is one of the strongest ones visible from the earth. In 1964, it was first discovered during a rocket flight. Cygnus X–1 is about 6,100 light years away from the earth.
Sadr Region–IC 1318: It is basically an emission nebula in this constellation formed around the star Sadr; it is located at the intersection of the Northern Cross.

The other notable deep sky objects of this constellation are the North America Nebula (Caldwell 20), Pelican Nebula, Crescent Nebula (Caldwell 27), Cygnus Loop (Sharp–less 103) and Veil Nebula (IC 1340).

What is its position in the galaxy?

Cygnus lies in the fourth quadrant of the northern hemisphere and can be seen at latitudes between +90° and -40°.

How much space does it occupy in the sky?

It occupies an area of 803 square degrees, making it the 16^th largest constellation in the night sky.

What is the cultural and mythological significance of Cygnus?

The constellation Cygnus has an uncertain identity. In one myth, it could be Zeus who is likely to seduce Leda, the mother of Helen of Troy. In another myth, Cygnus is represented as a friend of Phaethon, the son of Apollo, the sun god. While trying to drive the sun–gods chariot, Phaethon fell into the river Eridanus. Cygnus repeatedly searched into the water for Phaethon and hence, Zeus turned it into a swan out of pity and compassion.

Which are its neighbouring constellations?

Cygnus is surrounded by constellations like Cepheus, Draco, Lacerta, Lyra, Pegasus and Vulpecula.

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