Final answer:
The planets, satellites, and other members of the solar system likely formed together with the Sun in a giant, spinning cloud of gas and dust called the solar nebula. Material in the solar nebula first coalesced into planetesimals, which eventually formed the planets and moons.
Step-by-step explanation:
The planets, satellites, and other members of the solar system likely formed together with the Sun in a giant, spinning cloud of gas and dust called the solar nebula. This hypothesis is supported by regularities observed among the planets, as well as similar circumstellar disks observed around other stars. Within the solar nebula, material first coalesced into planetesimals, which eventually gathered together to form the planets and moons.