Stars: Properties and Classification

Brightness is different from Luminosity
n Luminosity – the total amount of power being released
from a star (this is an intrinsic property of the star).
n Brightness – the power from that star that actually gets
to us. This is the quantity we measure with a telescope.
A Stars brightness depends on its distance from us.
- there are stars much more luminous than our sun
in the sky, however, they are not nearly as bright because
they are far away.
A stars apparent brightness B = luminosity
4π (distance) 2 =
L
4π d 2