Meet a star / Scorpius

Xamidimura

Xamidimura is a blue-white star, far hotter than the Sun, in the constellation Scorpius. It is a subgiant: a star just beginning to leave the long, steady part of its life.

A drawing in the star's own colour, worked out from its measured colour index. It is not a photograph.

How far

500 light years

The light you see from Xamidimura tonight set off about 500 years ago. Everything we know about it is that much out of date.

Distances this great are hard to measure, and this one could be out by a fifth or more.

How bright

1,300 Suns

It gives out 1,300 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 3.00. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.

How hot

Hotter than 13,000 K

That is the temperature of its surface, worked out from its colour, so it is a guide and not a measurement. For stars as blue as this one, colour is a poor thermometer: most of their light is ultraviolet, which the eye and this sum do not see, and the true figure can be far higher. 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.

XamidimuraThe Sun

In your sky now

Working it out…

Its names

Its own name
Xamidimura
By constellation (Bayer)
Mu-1 Scorpii
Hipparcos catalogue
HIP 82514
Henry Draper catalogue
HD 151890
Spectral type
B1.5IV + B

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.