Tau Cygni
Tau Cygni is a yellow-white star, a little hotter than the Sun, in the constellation Cygnus. It is a subgiant: a star just beginning to leave the long, steady part of its life.
How far
66 light years
The light you see from Tau Cygni tonight set off about 66 years ago. Everything we know about it is that much out of date.
How bright
12 Suns
It gives out 12 times as much visible light as the Sun. It can be seen by eye away from bright lights.
Astronomers put its brightness in our sky at magnitude 3.74. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.
How hot
About 6,900 K
That is the temperature of its surface, worked out from its colour, so it is a guide and not a measurement. It could be out by a few hundred degrees. The Sun's is 5,772 K. Hotter stars are bluer and cooler stars are redder, the same way a poker in a fire goes from red to white.
Tau CygniThe Sun
In your sky now
Working it out…
Its names
It has no name of its own. Its name by constellation is a Greek letter and the constellation it is in, a way of naming begun by Johann Bayer in 1603.
- By constellation (Bayer)
- Tau Cygni
- Hipparcos catalogue
- HIP 104887
- Henry Draper catalogue
- HD 202444
- Spectral type
- F1IV
Where this comes from
Distance, brightness, colour and spectral type are from the HYG star database, version 4.4, by David Nash, shared under a Creative Commons Attribution-ShareAlike 4.0 licence. Its distances are those measured by the Hipparcos satellite. The temperature is worked out here from the colour with the formula of Ballesteros (2012), and the words are written for this site.
To read more: Colour and brightness, How stars live and die, Measuring distance.