During her presentation on exoplanets, Johana explains to the class that while Proxima-b and TRAPPIST-1e may potentially be able to support life, with each of these planets, one side of the planet always faces the sun, making that side perpetually hot and the dark side eternally cool. What term does Michelle use to describe this?

extinguishable
tidally unlocked
tidally locked
bipolar

Johana uses the term "tidally locked" to describe the phenomenon where one side of a planet always faces the sun.