25 Canum Venaticorum
25 Canum Venaticorum is a white star, hotter than the Sun, in the constellation Canes Venatici. It is a giant: a star that has used up the hydrogen in its core and swollen up.
How far
200 light years
The light you see from 25 Canum Venaticorum tonight set off about 200 years ago. Everything we know about it is that much out of date.
At this distance the figure could be out by a tenth or so.
How bright
38 Suns
It gives out 38 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 4.82. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.
How hot
About 7,900 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.
25 Canum VenaticorumThe Sun
In your sky now
Working it out…
Its names
It has no name of its own. Its name by constellation is a number and the constellation it is in, from the catalogue of John Flamsteed, the first Astronomer Royal.
- By constellation (Flamsteed)
- 25 Canum Venaticorum
- Hipparcos catalogue
- HIP 66458
- Henry Draper catalogue
- HD 118623
- Spectral type
- A7III
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.