Question: When a star exhausts its hydrogen supply, that's a tell sign that its near the end of its life. Is it possible to transfer more hydrogen into the star before it collapses in order to ensure it lives longer?

Nick Wright answered on 13 Mar 2014:

That’s a good idea but you’d have to get the hydrogen to the core of the star because that’s where the nuclear reactions take place. It’s only in the core of the star where the star actually runs out of hydrogen – throughout the rest of the star’s atmosphere there is lots of hydrogen, but you’ve got to get it into the core. It’s tough to get things into the core because its small, very dense, and there’s a lot of energy pushing outwards from the core. The star does naturally mix throughout its layers but it only replenishes a bit of the hydrogen supply in the core, and not enough to extend the star’s life.

If you had the power to replenish a star’s hydrogen supply you would also have enough energy to move everyone on Earth to another solar system, which would probably be an easier option for a civilisation around a dying star.