The star Alderamin has an apparent magnitude of 2.4 and an absolute magnitude of 1.4.From this information (assuming that the starlight has not been dimmed by interstellar clouds),we can say for certain that Alderamin is
A) less than 10 AU away.
B) more than 10 parsecs away.
C) less than 10 light-years away.
D) less than 10 parsecs away.

Question

Quizplus · Accepted Answer

The relationship between apparent magnitude, absolute magnitude, and distance is given by the formula for calculating distance in parsecs based on the difference between a star's apparent and absolute magnitudes. Since Alderamin's absolute magnitude is brighter than its apparent magnitude, it indicates that the star is farther away than 10 parsecs. The formula implies that if a star's absolute magnitude is brighter than its apparent magnitude, the star must be more than 10 parsecs away, because an absolute magnitude is defined as the apparent magnitude a star would have if it were 10 parsecs away.

The Star Alderamin Has an Apparent Magnitude of 2