Apparent magnitude measures the intensity of starlight received on earth. The larger the distance of a star, the lower is its apparent magnitude (farther object looks dimmer). Absolute magnitude measures the brightness a star would have if it was placed at a distance of 10 pc away it depends only on the star's intrinsic brightness it measures the luminosity of a star Luminosity: Total amount of energy that the star radiates in 1 second. It is determined by a combination of two factors: A giant star has a large surface area for light emission large luminosity A hot star has a high surface temperature and emits more light large luminosity e.g., a hot star with a large surface area must be luminous, a cool star with a small surface area must be dim, however, a cool star could be luminous if it has a very large surface area.