Why is a 1 solar-mass red giant more luminous than a 1 solar-mass main-sequence star?
A)The red giant has a hotter core.
B)The red giant's surface is hotter.
C)The red giant is more massive.
D)Fusion reactions are producing energy at a greater rate in the red giant.

Question

Quizplus · Accepted Answer

The red giant is more luminous because fusion reactions are producing energy at a greater rate in the red giant than in a main-sequence star. As the red giant has exhausted the hydrogen fuel in its core and fusion now occurs in a shell around the core where compression and temperature are higher. This makes the red giant brighter and more luminous than a main-sequence star of the same mass.

Why Is a 1 Solar-Mass Red Giant More Luminous Than