I am currently brainstorming a hard (like the hardest possible; everything that occurs in the story must at least be theoretically possible) sci-fi story which will take place far in the future. I don't have a specific year in mind yet but it has to be far in to the future enough that humans theoretically have the capacity to create a machine which could prevent the sun's rapid loss of hydrogen. Many articles (including this one: https://www.google.com/amp/s/phys.org/news/2015-02-sun-wont-die-billion-years.amp) I have read estimate that the Earth has roughly a billion years left until the sun increases in luminosity such that the Earth's oceans evaporate and all life dies.
Is it theoretically possible that humans could build a machine that will prevent the sun from increasing in luminosity to the point where it kills all life? The sun emits more energy the more hydrogen is burned but is it possible to lower the amount of energy the sun emits? To be clear, I am not asking for people to provide ideas of how humanity could prevent the sun from increasing in luminosity. I am asking if it would ever be theoretically possible to do so. If it is, why? If not, why not? In my story, human beings are flourishing and would have access to anything that will or theoretically will exist.