Distance modulus

The distance modulus is a way to figure out how far away something is. Let’s say you have an ordinary flashlight that you can shine on a wall in your bedroom. You can measure how far away the wall is by the size of the flashlight’s beam on the wall. The farther away the wall is, the smaller the beam will look. The distance modulus uses something similar to figure out how far away stars are. Instead of a flashlight beam, it uses the brightness of the stars. The farther away a star is, the less bright it will look. The distance modulus is a way to measure how much dimmer a star looks from far away, so we can figure out how far away it is!