Just as a low-mass main sequence star runs out of fuel in its core, it actually becomesbrighter. How is this possible?

Question

Quizplus · Accepted Answer

As the core of a low-mass main sequence star runs out of fuel, it contracts under the force of gravity. This contraction raises the temperature and pressure in the core, allowing the outer hydrogen shell to ignite and begin burning more vigorously. This increase in energy generation causes the star to become brighter, despite the fact that its core is running out of fuel. As the core of a low-mass main sequence star runs out of fuel, gravity causes it to contract. This contraction heats up the core, allowing hydrogen shell-burning to occur in a larger region around the core. This produces more energy, causing the star to become brighter despite the fact that its core is running out of fuel.

Just as a Low-Mass Main Sequence Star Runs Out of Fuel