GENERAL KNOWLEDGE

Detailed explanation-1: -absolute brightness: The apparent brightness a star would have if it were placed at a standard distance of 10 parsecs from Earth.

Detailed explanation-2: -However, the brightness of a star depends on its composition and how far it is from the planet. Astronomers define star brightness in terms of apparent magnitude-how bright the star appears from Earth-and absolute magnitude-how bright the star appears at a standard distance of 32.6 light-years, or 10 parsecs.

Detailed explanation-3: -Apparent magnitude m of a star is a number that tells how bright that star appears at its great distance from Earth. The scale is “backwards” and logarithmic. Larger magnitudes correspond to fainter stars.

Detailed explanation-4: -Notice that as the distance increases, the light must spread out over a larger surface and the surface brightness decreases in accordance with a “one over r squared” relationship. The decrease goes as r squared because the area over which the light is spread is proportional to the distance squared.