Standard Candles

Imagine that you have a type of star which is easy to recognise and is always exactly the same - two stars of this type will look identical if you put them next to each other.

Stars like this are called Standard candles.

However, if you have two of these stars and one is further away than the other, the more distant one will look fainter.

If you can find them, you can always work out the relative distances between them by comparing how bright they look.

There are many different kinds of Standard Candle star with the best letting us measure the distance to nearby galaxies - millions of light years away.