What process powers mature stars like our Sun once they form?

Answer

Sustained, long-term nuclear fusion of hydrogen into helium

Once the ignition threshold is met, the object settles onto the main sequence, where its energy source becomes the sustained, long-term nuclear fusion of hydrogen into helium, replacing gravitational contraction as the primary power source.

What process powers mature stars like our Sun once they form?
protostarstar formationastrophysicsenergy generation