How Callisto Formed

There are two ways for a moon to form: accretion and gravity or impact. Jupiter's moon, Callisto formed using accretion and gravity. The Six steps Callisto took towards forming are as follows: First a supernova occurred, then came a nebula. Hot gas and dust left over from the Supernova's explosion swirled around in space. As the cloud cooled atoms started to move slower, therefore clumping together. Then Planetesimals formed and accretion began. Callisto gathered together using the gas and dust that surrounded Jupiter. Then Callisto became a proto Planet and grew to it's full size, however because Callisto did not have enough mass in order to 'clear its neighborhood' of debris. The final step of Callisto's formation was to get caught inside Jupiter's orbit, Where it is even today.