ABSTRACT
The bodies of the solar system formed 4650 million years ago (4.65 Gy [gigayears]) togetherwiththeSunfromamassofgas,mainlyhydrogen,mixedwithsmallquantitiesofheavierelementsformedinolderstars,andsomeadditionaldust.Gravitational contractionofthismassandtheformationoftheprotoplanetarydiskduetoangular momentumconservationwerethe˜rststepsintheformationofthesystem.Whereas most of the mass was concentrated at the center of gravity of the system, forming theSun,about1%remainedinthedisk,becomingtheprimematerialforforming theplanets,satellites,andotherminorbodies.Theactionofgravitycombinedwith magneticforcesandviscouseffectsredistributedthemassandangularmomentum withinthedisktoreacha˜naldistributioninwhichabout99.9%ofthemassand2% of the total angular momentum of the system reside in the Sun.
