Red dwarfs are fully convective, circulating hydrogen throughout the star, which prevents core depletion and allows them to burn fuel efficiently for trillions of years.
This efficiency affects predictions of stellar lifespan and evolution.
It also provides a natural laboratory for studying fusion in low-mass stars.
Red dwarfs mix their fuel so well that they never run out, at least not for trillions of years.
[ESA, esa.int]