Cygnus constellation
Cygnus (the Swan) is a constellation in the northern sky, best seen in the evening in September. Its brightest star is Deneb (magnitude 1.25). It contains the Northern Cross. Cygnus covers 804 square degrees and is the 16th-largest of the 88 constellations.
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How to find Cygnus, step by step
The Northern Cross in the Summer Triangle.
- On summer and autumn evenings find the Summer Triangle almost overhead: Vega (brightest), Deneb and Altair.
- Deneb is the tail of the swan and the top of the Northern Cross.
- From Deneb the long axis runs through Sadr to Albireo, the swan's head, which lies in the middle of the Milky Way.
- The cross bar (Fawaris, Sadr, Aljanah) forms the wings.
Detailed star map of Cygnus
Facts
| Latin name | Cygnus (genitive: Cygni) |
|---|---|
| Abbreviation | Cyg |
| Meaning | the Swan |
| Area | 804 square degrees (16th of 88) |
| Location | right ascension 20.6 h, declination +44° |
| Visible from | latitudes 90° N to 29° S (whole constellation) |
| Best month | September (at about 9 pm) |
| Brightest star | Deneb |
| Stars brighter than magnitude 6 | 139 |
| Named stars (IAU) | 6 |
| Messier objects | M29, M39 |
| Neighbors | Cepheus, Draco, Lacerta, Lyra, Pegasus, Vulpecula |
How to find Cygnus
From 40° N (the USA, southern Europe, Japan) look north in September evenings: at about 9 pm Cygnus stands highest, around 86° above the northern horizon. From 35° S (Australia, South Africa, Argentina) it is highest in the north, about 11° above the horizon. The months before and after (August and October) are also good: then it is up a couple of hours earlier or later.
Cygnus borders Cepheus, Draco, Lacerta, Lyra, Pegasus and Vulpecula.
Asterisms with stars in Cygnus: Summer Triangle, Northern Cross.
Stars of Cygnus
Cygnus has 139 stars brighter than magnitude 6, the limit of the naked eye under a dark sky. These are the brightest:
| Star | Designation | Magnitude | Type | Distance |
|---|---|---|---|---|
| Deneb | α Cygni | 1.25 | A2Ia | 1,640 ly |
| Sadr | γ Cygni | 2.2 | F8Ib | 1,826 ly |
| Aljanah | ε Cygni | 2.46 | K0-III | 76 ly |
| Fawaris | δ Cygni | 2.87 | B9.5IV+F1V | 167 ly |
| Albireo | β1 Cygni | 3.08 | K3II+B9.5V | 328 ly |
| — | ζ Cygni | 3.2 | G8+III-IIIaBa0.6 | — |
| — | τ Cygni | 3.72 | F2IV | — |
| — | ξ Cygni | 3.72 | K4.5Ib-II | — |
| — | κ Cygni | 3.77 | G9III | — |
| — | 31 Cygni | 3.79 | K2II+B3V | — |
| — | ι2 Cygni | 3.79 | A5Vn | — |
| — | η Cygni | 3.89 | K0III | — |
Deep-sky objects in Cygnus
Cygnus contains 2 objects from Charles Messier's catalog:
- Messier 29 (M29): open cluster, 6.6 mag
- Messier 39 (M39): open cluster, 4.6 mag
Printable Cygnus map and outline
A black and white version for printing and a plain outline of the Cygnus figure, useful for school projects, worksheets and learning to recognize the shape.
History
Cygnus is one of the 48 constellations listed by Ptolemy in the Almagest (2nd century AD). Its official boundary was drawn by Eugène Delporte for the International Astronomical Union in 1930.
Questions about Cygnus
What is the brightest star in Cygnus?
Deneb, at magnitude 1.25, about 1,640 light-years away.
When can you see Cygnus?
Cygnus is best seen in the evening in September. The whole constellation is visible from latitudes between 90° N and 29° S.
How many stars are in Cygnus?
139 stars in Cygnus are brighter than magnitude 6 and can be seen with the naked eye under a dark sky; 6 of them have official IAU names.
What does Cygnus mean?
Cygnus means “the Swan” in Latin. Its abbreviation is Cyg and the genitive, used in star names such as α Cygni, is Cygni.
