1. The Sun’s radiation is derived by fusing hydrogen into helium, which converts mass to
energy. How many years does it take the Sun to reduce its mass by an amount equal to
the mass of Earth? Show how you got your answer.
(A) 1 million years
(B) 5 million years
(C) 25 million years
(D) 45 million years
(E) 90 million years
2. Some of the stars visible tonight are the same as our Sun, but they look very faint
because they are much farther away. If a star like our Sun is 10 parsecs from Earth, how
bright is it compared to our Sun? Show how you got your answer.
(A) 10−7 × Sun’s brightness
(B) 10−9 × Sun’s brightness
(C) 10−11 × Sun’s brightness
(D) 10−13 × Sun’s brightness
(E) 10−15 × Sun’s brightness