# Deneb (Alpha Cygni)

Deneb (Alpha Cygni) is a star in the constellation Cygnus, magnitude 1.3.

**The tail of the Swan — a supergiant tens of thousands of times brighter than the Sun.**

Deneb looks modest beside Vega, yet it is in another league. It is a white supergiant of about 19 solar masses, shining with somewhere between 55,000 and 196,000 times the Sun’s light — its distance is so uncertain that nobody knows exactly. Put in the Sun’s place, it would reach at least to the orbit of Mercury, perhaps to Earth’s. It may be the most distant of the 30 brightest stars.

It began as a hot blue star of about 23 solar masses and has already used up its core hydrogen. A strong wind strips away roughly an Earth’s worth of gas every 500 years, and within a few million years it will explode as a supernova. Meanwhile it flickers irregularly: Deneb is the prototype of the Alpha Cygni [variable stars](https://astropilot.space/glossary/variable-star).

Its name comes from the Arabic for ‘tail’, from dhanab al-dajājah, ‘the tail of the hen’.

Deneb (Alpha Cygni) is 1,400 light-years away: the light we see from it set off around AD 630, 90 years after the Hagia Sophia was completed in Constantinople.

## Did you know?

- **A future pole star.** Earth’s wobbling axis will bring the north celestial pole within about 7° of Deneb around AD 9800.
- **Mars’s pole star.** The north pole of Mars points to a spot halfway between Deneb and the star Alderamin.
- **The parson’s nose.** Deneb has gathered many names. The German poet Philippus Caesius called it Os rosae, and also Uropygium — the parson’s nose.

A bright white star marking the tail of Cygnus and the head of the Northern Cross. It is the faintest corner of the big triangle it makes with Vega and Altair. Sweep binoculars around it: it sits in rich Milky Way star fields.

## When and where to see it

It is best placed in the evening sky around September, when it crosses the meridian at about 10 pm local time (around midnight in July). It can be seen from everywhere north of 45°S and never sets north of 45°N.

At its highest it stands 85° up from 50°N, 80° up from 35°N, 45° up from the equator, 10° up from 35°S.

## Facts

- Type: Star
- Constellation: Cygnus
- Designations: Alpha Cygni, α Cyg, 50 Cyg, HR 7924, HD 197345, HIP 102098
- Magnitude: 1.3
- Position: RA 20h 41.4m, Dec +45° 17′ (J2000)
- Spectral type: A2Ia
- Colour: white (B−V 0.09)
- Distance: 1,400 light-years
- Discovered: Known since antiquity

Open AstroPilot to see when Deneb (Alpha Cygni) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view. https://astropilot.space/object/deneb