Question

When the core of a star like the sun uses up its supply of hydrogen for fusion, the core begins to ________?

Answer 1

Answer: shrink and heat

Stars similar to our Sun use hydrogen as fuel, creating helium in the process of nuclear fusion.

Now when the hydrogen is used up, the core of the star reaches such a temperature that begins to transform the helium into carbon. That is, the core heats up more due to the continuous fusion reactions and shrinks because it will not have enough pressure to maintain its size.