How do planets get moons?

Answer 1

Most moons are formed at the same time as their planets, and are made of similar materials. After the formation of the sun, the leftover protoplanetary material eventually clumped together and formed planets. Any material left over from the formation of the planets later formed the moons. The Earth's moon, however, is believed to have been formed by a collision with a NEO (Near Earth Object), such as an asteroid, that scientists call Theia. The collision sent billions of tons of material into space and reaccreted into a spherical shape. They speculate that it was the size of Mars and hit Earth about 4.5 billion years ago while the Earth was still relatively young.

Answer 2

Moons are formed when a planet captures a passing object in its gravitational pull, or when a large celestial body collides with a planet, causing debris to form a moon. Another theory suggests that moons can also form from the leftover material that was swirling around a planet as it was forming.