Society for Popular Astronomy

Variable stars

Stars are not all unchanging points of light. Many vary in their brightness, for various reasons. They are known, unsurprisingly, as variable stars.

These variations can happen over time scales ranging from hours to weeks and months. The SPA has an observing section that can help you to learn more about these stars and see them for yourself.

The causes of their brightness variations can be due to physical changes happening in the stars themselves, or other effects like another object blotting out the starlight.

Many thousands of variable stars are known, and a small number can even be seen with the unaided eye. Many more may be viewed with binoculars.

This chart shows the location of Mira, a long-period variable star in the constellation of Cetus.

Observing variable stars and following their brightness changes is an area of stargazing that is not just fun to do, but can also help provide data that professional astronomers find useful.

When you join the SPA, you can take part in an observing programme run by our Variable Star Section which follows a number of the brighter stars to fluctuate in brightness. You don’t even need a telescope.

Click to visit the Variable Star Section