Starmie swims through water by spinning its star-shaped body as if it were a propeller on a ship. The core at the center of this Pokémon’s body glows in seven colors. At the center of its body is a red core, which sends mysterious radio signals into the night sky. Its central core glows with the seven colors of the rainbow. Some people value the core as a gem.
Pokédex entry #121
starmie in Pokémon GO
It's possible to hatch starmie from an egg?
No, starmie can't be hatched.
Which are starmie’s strengths and weaknesses?
starmie is a psychic and water type Pokémon. psychic type pokémons are strong against fighting, poison, ghost pokémons but weak against bug, shadow pokémons. water type pokémons are strong against fire, ground, rock pokémons but weak against water, grass, dragon, electric pokémons.