Question

An unnamed star is found to have an apparent magnitude of +5.1 and an absolute magnitude of -6.0. What can we conclude about its distance from us? Explain your reasoning.

Answer 1

The absolute magnitude of a star is the apparant magnitude measured at a distance of 10pc from it, where apparant magnitude is the measure of its flux recieved by the Earth.

The apparant and the absolute magnitude are related by the equation,

Where M is the absolute magnitude and 'm' is the apparant magnitude.

r is the distance of the star from the Earth, F is the flux recieved,

Now,

Hence, the above equation will transform to,

ie,

Given, m=5.1,M=-6.0

Hence,

Hence, the star is 1659.58pc away from the Earth.