Units for measuring the brightness of stars

The unit used to measure the brightness of stars is the magnitude ^? : 200 years BC, Hipparchus classified visible stars between magnitude ^? 0 for the brightest star in the sky and 6 for the faintest stars visible to the naked eye. In the 19th century, the first photometric measurements showed that first magnitude ^? stars are about 100 times brighter than sixth magnitude ^? stars. The formula below allows us to keep these intervals approximately.

$$ m= -2,5 \times log ( \frac{L}{L_0} ) $$

where L is the flux of light from the star reaching Earth and L0 is the flux from a star of magnitude ^? 0.
A magnitude ^? that is 5 times greater corresponds to a star that is 100 times less bright.
Caution is however required, because a star may appear less bright because it is far away. To compare stars, we define their absolute magnitude ^? , that is the magnitude ^? they would have at a fixed distance of 10 parsecs ^? .