How long will the Sun have spent as a main-sequence star when it finally begins to evolve toward the red giant phase?

Question

Quizplus · Accepted Answer

The Sun will have spent approximately 10 billion years as a main-sequence star before it begins to evolve into the red giant phase. This is because the Sun is a G-type main-sequence star (or G dwarf star), and its main-sequence lifetime is determined by its mass and the rate at which it fuses hydrogen into helium in its core.

How Long Will the Sun Have Spent as a Main-Sequence