According to the Stefan-Boltzmann Law, what causes the Red Giant phase to be vastly more luminous than the Main Sequence star?
Answer
The massive increase in surface area ($A$) overwhelms the drop in surface temperature ($T$).
Luminosity is proportional to surface area multiplied by the fourth power of absolute temperature ($L \propto A T^4$). Even though the temperature drops, the enormous expansion leads to a vast increase in surface area, dominating the equation and resulting in higher total luminosity.
Frequently Asked Questions
What maintains the stable equilibrium of a star, like our Sun, while it is on the Main Sequence?What is the immediate trigger for the dramatic expansion of a Sun-like star into a Red Giant?According to the Stefan-Boltzmann Law, what causes the Red Giant phase to be vastly more luminous than the Main Sequence star?What causes the surface color of an evolved star to shift toward the red end of the spectrum?For a star similar in mass to the Sun, approximately how much can its total luminosity increase upon becoming a Red Giant?What is the primary difference in the mechanism driving energy output between a Main Sequence star and a Red Giant?Which class of stars evolves into the even grander objects known as Red Supergiants?What physical concept distinguishes between 'flux' and 'luminosity' in stellar physics?What governs the visual color of a star, linking it directly to its surface temperature?What astronomical phenomenon allows astronomers to observe Red Giants in distant galaxies across cosmological distances?What is the approximate radius change a Sun-like star experiences when expanding into a Red Giant?