# Intensity and flux

1. Mar 13, 2005

### orange

Hey everyone!

What is really the difference between flux and intensity in astronomy? What I understand they are two different words of the same thing, namely energy per square length unit per time unit.

I appreciate any help, thanks alot!

2. Mar 13, 2005

### SpaceTiger

Staff Emeritus
There are numerous conventions, but most of the ones I see define flux simply as power per unit area, while intensity is power per unit area per unit solid angle. The conceptual difference is that the flux is total brightness of an object, while intensity defines its brightness at a given position (for example, the projected center of a galaxy).