Recall, each magnitude corresponds to a factor of 2.5 in brightness. Referring to the chart on the previous page, can you answer these questions?




What is the difference in apparent flux of Venus and the Moon?


-4 - (-11) = 7 magnitudes difference. Each magnitude is a factor of 2.5. The difference in flux is 2.5 x 2.5 x 2.5 x 2.5 x 2.5 x 2.5 x 2.5 = 2.5⁷ = 600.




How much dimmer a star can be seen by the Hubble Space Telescope than can be seen by the naked eye?

2.5²⁴ = 3 x 10⁹ (3 Billion times dimmer!)




Two stars, A and B, have the same absolute magnitude. However, Star A has an apparent magnitude of 7, while Star B has an apparent magnitude of 2. Which star is closer? By how much??

The difference in magnitudes is 5. That represents a difference in flux of: 2.5 x 2.5 x 2.5 x 2.5 x 2.5 = 100. Star A is 100 times dimmer. Since the flux drops as the inverse square of the distance, the difference in distance must be the Square Root of 100. Star B is 10 times closer than Star A.




Star A and B have the same apparent magnitude. But we know that Star B has an absolute magnitude of 7, and that this is 2 magnitudes larger than A, which has an absolute magnitude of 5. Which star is Closer?







If I move a star to a distance twice as far away, how will that affect its:
a) Apparent Magnitude?
b) Absolute Magnitude?