Tejat
Tejat is a red star, among the coolest, in the constellation Gemini. It is a giant: a star that has used up the hydrogen in its core and swollen up.
How far
230 light years
The light you see from Tejat tonight set off about 230 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 Everything we know about it is that much out of date.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
310 Suns
It gives out 310 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 2.87. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.
How hot
About 3,600 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.
TejatThe Sun
In your sky now
Working it out…
Its names
- Its own name
- Tejat
- By constellation (Bayer)
- Mu Geminorum
- Hipparcos catalogue
- HIP 30343
- Henry Draper catalogue
- HD 44478
- Spectral type
- M3IIIvar
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.