Distance Modulation

Way of measuring the distance of stars or galaxies from the earth is called distance modulation. The technique is based on the fact that stars appear less bright with increasing distance from the earth. Astronomers work out how bright a star actually is and compare this with the brightness it assumes in the sky. This difference, the distance modules, can be used to estimate the star’s distance. The absolute magnitude can usually be estimated from the nature of the star’s spectrum.