The true brightness of a star is called its absolute magnitude.

Here's why:

* Absolute magnitude measures a star's intrinsic brightness, as if it were observed from a standard distance of 10 parsecs (about 32.6 light-years). This allows for a fair comparison of the actual luminosities of different stars, regardless of their distance from Earth.

* Apparent magnitude is the brightness we see from Earth, which is influenced by both the star's true brightness and its distance.