Eta Herculis
Eta Herculis is a yellow star, much like the Sun in temperature, in the constellation Hercules. It is a giant: a star that has used up the hydrogen in its core and swollen up.
How far
110 light years
The light you see from Eta Herculis tonight set off about 110 years ago. Everything we know about it is that much out of date.
How bright
39 Suns
It gives out 39 times as much visible light as the Sun. It is easy to see by eye on a clear night.
Astronomers put its brightness in our sky at magnitude 3.48. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.
How hot
About 5,000 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.
Eta HerculisThe 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)
- Eta Herculis
- Hipparcos catalogue
- HIP 81833
- Henry Draper catalogue
- HD 150997
- Spectral type
- G8III-IV
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.