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

Question

Quizplus · Accepted Answer

A red giant is a star that has exhausted most of the hydrogen fuel in its core and has moved into a later stage of its evolution. As the core contracts, outer layers of the star expand and cool, which makes the red giant larger and more luminous. While a main sequence star is still fusing hydrogen in its core, a red giant is fusing heavier elements like helium and carbon. These fusion reactions produce energy at a greater rate, making the red giant more luminous than a main sequence star of the same mass.

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