How many stars in a constellation, and why don’t they change?

We explore the curious questions that science can answer

The Southern Cross has more stars than most other constellations (Getty/iStock)

How many stars are there in a constellation?

The number varies a lot. They are counted by measuring the number of stars that can be seen in an area of the sky. The Southern Cross has lots of stars – 19.6 per 100 square degrees of sky. Most others have between five and six per 100 degrees.

An easier way is to count the number of bright stars. In the northern hemisphere, Centaurus has 18 bright stars. Canis Minor has only two.