absolute magnitude

In astronomy, measure of the intrinsic brightness of a celestial body in contrast to its apparent brightness or magnitude as seen from Earth.

For a non-self-luminous body, such as an asteroid, the absolute magnitude is the magnitude it would appear to have if it were one astronomical unit (149.6 million km/92.6 million mi) from both the Sun and the Earth with the phase angle zero. For a self-luminous body, such as a star or galaxy, the absolute magnitude is the magnitude it would appear to have if it were at a distance of 10 parsecs or 32.616 light years.