Why are stars so bright?

Stars appear bright based on their distance from Earth and their stellar classification. The measurement used to indicate the brightness of a star as seen from Earth is called the apparent magnitude.

The apparent magnitude differs from a star's absolute magnitude, which describes its brightness from a set distance, rather than the varying distances of stars seen from Earth. The lower the apparent magnitude, the brighter the star is as seen from Earth. The brightest star that can be seen from Earth aside from the sun is Sirius, which is 8.6 light years away. Sirius has an apparent magnitude of minus 1.46.