Extinction by the interstellar medium dims starlight by about 2 magnitudes for every 1,000 pc the light travels.If a star is observed to have a magnitude of 7,and it is determined to be at a distance of 2,000 pc,what would the magnitude be if there was no extinction?
A) 7
B) 1.75
C) 28
D) 11
E) 3

Question

Quizplus · Accepted Answer

Extinction by the interstellar medium dims starlight by about 2 magnitudes for every 1,000 pc the light travels. So, for a distance of 2,000 pc, the extinction would be 4 magnitudes. Therefore, the magnitude without extinction would be 7 - 4 = 3.

Extinction by the Interstellar Medium Dims Starlight by About 2