the difference between brightness and luminosity?

Question

hi,

when people talk about a star's brightness and a star's luminosity, what do they mean?

am i right in describing brightness as the number of photons per second reaching us from the star?

and luminosity i have no clue about, just that its related to how massive a star is.

also,

if a star was shining with a bright blue light many, many times brighter than the sun, why would that indicate that this star is younger than the sun? is there any other way that i could determine the relative ages of the stars?

Answer 1

Brightness usually refers to luminosity per unit area; or how much light energy is emitted per square meter of surface area. The luminosity of the star is the total light energy the whole star emits. But since the stars are so far away, they seem like infinitely small dots and we just see all their luminosity as if it came from one point. In that case, brightness and luminosity are the same.

Answer 2

I thought luminosity was a measure of intrinsically how much power it puts out, and that brightness is a measure of how it *looks", which of course depends on how far away from it the viewer is.

I could be wrong, as I'm relying on my memory here...

Answer 3

luminosity is using the own mild of the article as in case of stars, they're luminous, the floor brightness is using the sunshine of megastar falling on the gadgets as in case of planets and moon, they have not got their own mild yet they shine because of the sunlight mild.

Answer 4

they're the same. Bright is a synonym of Luminous.