Science & history · Constellation guide
Cygnus, the swan
Cygnus, the swan, flies down the Milky Way with its wings outstretched. Its brightest stars make a large cross, the Northern Cross, with Deneb at the top.
About this picture
NASA/Goddard Space Flight Center Scientific Visualization Studio. Gaia DR2: ESA/Gaia/DPAC. Constellation figures based on those developed for the IAU by Alan MacRobert of Sky and Telescope magazine (Roger Sinnott and Rick Fienberg). NASA's page (opens in a new tab).
The map is a composite of 1.7 billion catalogued stars, not a photograph from one place: it shows stars far too faint for the eye, and no weather, Moon or city light. It is drawn here in this chart's projection, with each star where it was in 2000; the fastest-moving bright star has shifted about a minute of arc since, far less than a pixel here.
How to spot it: A large cross along the Milky Way, with Deneb at its head. Source (opens in a new tab)
Swan and cross
A swan to the Greeks, a cross to many observers today, flying along the Milky Way.
Ridpath (opens in a new tab) notes that the Northern Cross, as Cygnus is popularly called, is far larger and more distinctive than the Southern Cross. The Greeks saw in its shape the long neck, outstretched wings and stubby tail of a swan flying along the Milky Way, and Aratus described it as hazy in parts, a reference to the Milky Way behind it.
The NASA Night Sky Network (opens in a new tab) counts the Northern Cross as an asterism made by the swan's stars, and Cygnus's brightest star, Deneb, is one corner of the Summer Triangle.
Sources for this section Ian Ridpath, Star Tales: Cygnus (opens in a new tab); Kat Troche (Astronomical Society of the Pacific), Connecting the Dots with Asterisms, NASA Night Sky Network (2024) (opens in a new tab)
Deneb
Deneb looks modest, yet it is the most distant of all the first-magnitude stars.
Deneb marks the swan's tail; its name comes from the Arabic dhanab al-dajāja, “tail of the hen” (opens in a new tab), and the Greeks, surprisingly, had no name for it.
It is a highly luminous supergiant about 1,400 light-years away (opens in a new tab), the most distant of all the first-magnitude stars, and still magnitude 1.25 in ESA's list (opens in a new tab). To look that bright from so far away it must give out enormous amounts of light; brightness and distance explains why.
Sources for this section Ian Ridpath, Star Tales: Cygnus (opens in a new tab); ESA, Hipparcos: The 50 Brightest Stars (opens in a new tab)
Albireo
The swan's beak is a double star of two colours that any small telescope can split.
The swan's beak is Albireo (opens in a new tab), which small telescopes show as a beautiful coloured double star of green and amber, Ridpath's “celestial traffic light”.
The colours mark different surface temperatures, as for all stars: hotter stars look blue or white (opens in a new tab), cooler ones orange or red.
How to see it Aim a small telescope at the swan's beak, Albireo (opens in a new tab), at the end of the cross's long arm opposite Deneb, the tail.
Sources for this section Ian Ridpath, Star Tales: Cygnus (opens in a new tab); NASA Science, Stars in an Exoplanet World (opens in a new tab)
Cygnus X-1
One of the first X-ray sources ever found turned out to be the first black hole identified.
In 1964 a sounding rocket carrying X-ray detectors found eight sources; one, Cygnus X-1 (opens in a new tab), the brightest X-ray source in Cygnus, became the first object identified as a black hole.
NASA explains (opens in a new tab) that its visible companion is a blue supergiant catalogued as HDE 226868, orbiting in a little under a week; the X-rays come from the unseen partner.
Keep in mind The black hole itself cannot be seen. What a telescope shows at that spot is its companion, which NASA notes is seen in visible light (opens in a new tab).
Sources for this section NASA Imagine the Universe, More Information about Cygnus X-1 (opens in a new tab)
The Great Rift
Under a really dark sky, a dark lane splits the Milky Way through Cygnus.
The Night Sky Network (opens in a new tab) describes a dark lane cutting into the Milky Way from the Summer Triangle down toward Sagittarius, the Great Rift. It is massive clouds of dust lying between Earth and the inner parts of our Galaxy, blocking the light of the stars behind.
By this site's calculation (opens in a new tab), Cygnus stands almost overhead at its highest from 40°N and about 16° up in the north from 35°S, and is highest at about 9 p.m. local time in mid-September.
How to see it The Rift needs very dark skies (opens in a new tab), ideally dark, dry ones, eyes given time to adapt, and a new or crescent Moon; a full Moon washes it out.
Sources for this section Kat Troche (Astronomical Society of the Pacific), The Great Rift, NASA Night Sky Network (2025) (opens in a new tab); Bright Star Catalogue, 5th Revised Ed. (Hoffleit & Warren 1991), as computed by this site's star engine (opens in a new tab)
Where on Earth, and when
The whole key pattern rises from anywhere north of about 45°S.
South of about 62°S, none of it rises.
North of about 62°N, the whole key pattern never sets.
Its middle climbs at least 20° high, the finder's threshold for a suggestion, from anywhere north of about 31°S.
It is highest in the evening sky, at about 9 p.m. local time, in mid-September, from either hemisphere, wherever it rises. With daylight saving time, that is nearer 10 p.m. on the clock.
Worked out by this site from the Bright Star Catalogue, for a flat, clear horizon. Hills, buildings, haze and city light all cut into this; the air also lifts objects near the horizon by about half a degree. For your own place and night, use the sky finder.
Sources
- History Ian Ridpath, Star Tales: Cygnus (opens in a new tab) for the figure, Deneb, its name and distance, and Albireo · checked 27 September 2026
- Astronomy Kat Troche (Astronomical Society of the Pacific), Connecting the Dots with Asterisms, NASA Night Sky Network (2024) (opens in a new tab) for the Northern Cross as an asterism · checked 27 September 2026
- Astronomy ESA, Hipparcos: The 50 Brightest Stars (opens in a new tab) for Deneb's magnitude · checked 27 September 2026
- Astronomy NASA Science, Stars in an Exoplanet World (opens in a new tab) for colour and temperature · checked 27 September 2026
- Astronomy NASA Imagine the Universe, More Information about Cygnus X-1 (opens in a new tab) for Cygnus X-1 · checked 27 September 2026
- Astronomy Kat Troche (Astronomical Society of the Pacific), The Great Rift, NASA Night Sky Network (2025) (opens in a new tab) for the Great Rift and how to see it · checked 27 September 2026
- Astronomy Bright Star Catalogue, 5th Revised Ed. (Hoffleit & Warren 1991), as computed by this site's star engine (opens in a new tab) for its height from 40°N and 35°S, and best month
