Suppose astronomers could examine a star and determine its apparent magnitude M without any intervening gas and dust. Compared to its apparent magnitude measured with gas and dust between Earth and the star, this "clean" measurement of M would be
A) a larger number.
B) a smaller number.
C) the same number.
D) either larger or smaller depending on the star's speed (toward or away).

Question

Quizplus · Accepted Answer

The apparent magnitude of a star becomes larger (dimmer) when gas and dust are present between the star and the observer because these materials absorb and scatter some of the star's light before it reaches Earth. Without any intervening gas and dust, the star appears brighter, corresponding to a smaller number in the magnitude scale.

Suppose Astronomers Could Examine a Star and Determine Its Apparent