Theta Ursae Majoris
Theta Ursae Majoris is a yellow-white star, a little hotter than the Sun, in the constellation Ursa Major. It is a subgiant: a star just beginning to leave the long, steady part of its life.
How far
44 light years
The light you see from Theta Ursae Majoris tonight set off about 44 years ago. Everything we know about it is that much out of date.
How bright
8.5 Suns
It gives out 8.5 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 3.17. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.
How hot
About 6,500 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.
Theta Ursae MajorisThe 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)
- Theta Ursae Majoris
- Hipparcos catalogue
- HIP 46853
- Henry Draper catalogue
- HD 82328
- Spectral type
- F6IV
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.