red-dwarfs

The Sun has about 5 billion years left. The last stars in the universe will burn for 10 trillion. After they go out, the cosmos enters an era so dark and cold that physics itself may eventually dissolve the matter we're made of.

Tidal locking occurs when a body's rotation period equals its orbital period, so one hemisphere permanently faces its partner. The Moon is locked to Earth, which is why we always see the same face, and the same effect probably shapes planets around red dwarf stars.