# AST 111 Lecture Notes - Lecture 13: Supernova Remnant, 2Mass, Planetary Nebula

## Document Summary

This is a measure of the luminosity , or intrinsic brightness. The total amount of power the start radiates into space. Where as apparent brightness , or how bright it seems to be. Is the amount of starlight reaching earth (what we see) This does change because it depends on the formula below. The same amount of starlight passes through each sphere. The surface area of a sphere depends on the square of its radius. So the amount of the light passing through each unit of area depends on the inverse square. 4 this is what they uses before machines. Then they started to realize that there are things even brighter than one, go negititive. A magnitude 1 star is 100 times brighter than a magnitude 6 start (it goes by 5) A pair of stars where we can actually see both of them. This is a lot like the astrometric method from exoplanets.