Kapteyn's Star
Kapteyn's Star is a red star, among the coolest, in the constellation Pictor. It is in the long, steady part of its life, making helium from hydrogen in its core, as the Sun is.
How far
13 light years
The light you see from Kapteyn's Star tonight set off about 13 years ago. Everything we know about it is that much out of date.
How bright
0.00 of a Sun
It gives out one 260th of the Sun's visible light. It is too faint to see without a telescope.
Astronomers put its brightness in our sky at magnitude 8.86. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.
How hot
About 3,700 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.
Kapteyn's StarThe Sun
Its names
- Its own name
- Kapteyn's Star
- Hipparcos catalogue
- HIP 24186
- Henry Draper catalogue
- HD 33793
- Spectral type
- M0V
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.