A large body of matter in orbit around the sun or a star and thought to be developing into a planet: this analysis supported the view that the moon originated from a glancing collision between the earth and another protoplanet 4,500 million years ago
More example sentences
- Learning more about the protoplanet won't be fast or easy.
- The protoplanet candidate orbits about 70 times further from its star than Earth does from the Sun.
- It isn't clear how the latest suspected protoplanet is being formed.
Definition of protoplanet in:
- The US English dictionary