Alkaphrah
Alkaphrah is a white star, hotter than the Sun, in the constellation Ursa Major. It is in the long, steady part of its life, making helium from hydrogen in its core, as the Sun is.
How far
360 light years
The light you see from Alkaphrah tonight set off about 360 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 Everything we know about it is that much out of date.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
390 Suns
It gives out 390 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 3.57. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.
How hot
About 10,000 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.
AlkaphrahThe Sun
In your sky now
Working it out…
Its names
- Its own name
- Alkaphrah
- By constellation (Bayer)
- Kappa Ursae Majoris
- Hipparcos catalogue
- HIP 44471
- Henry Draper catalogue
- HD 77327
- Spectral type
- A1Vn
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.