Final answer:
Stars that are very hot but not very bright are called white dwarfs.
Step-by-step explanation:
The stars that are very hot but not very bright are called white dwarfs.
White dwarfs are stars at the lower-left corner of the Hertzsprung-Russell (H-R) diagram. They have high surface temperatures, but their overall brightness is low because they have a very small total surface area. This means that each square meter on a white dwarf puts out a lot of energy, making them hot, but their small size results in low overall brightness.
White dwarfs are formed during the late stages of stellar evolution when a star with a low or medium mass, like our Sun, exhausts its nuclear fuel and collapses under its own gravitational pull.