Presentation on theme: "CH 25.5 Solar System Formation"— Presentation transcript:
1 CH 25.5 Solar System Formation Objectives:How did our solar system form?What evidence supports our ideas?
2 Nebular TheoryThe solar system formed from a cloud of dust and gas (nebula). 4.6 billion years ago Nebula produced by the explosion of a previous star.National Geographic’s: Birth of the Solar System
3 Protoplanetary DiskProtoplanetary disk forms when gravity pulls particles and gas to the center. Disk begins to spin (possibly because of a shock wave from a “nearby” supernova. Gravity continues to contract the cloud to the center – making it spin faster (angular momentum … think ice skaters spinning) Protosun at center Sun when temperatures reach millions of degrees and NUCLEAR FUSION BEGINS. Nuclear fusion combines hydrogen atoms together to make helium and releases LOTS of ENERGY! Stars begin to shine!
4 Planets Grow by Accretion Accretion: Growth by colliding and sticking togetherParticles must be liquid or solid to stick together. They must COOL DOWN and CONDENSE from gas liquid!Planetessimals (asteroid size) Protoplanets (moon size) Planets
5 Inner vs. Outer PlanetsInner Solar System = “Rocky” Planets Hotter Metals & Rock condense (gas higher temps.Not made of H or He b/c …Solar wind blows light gases to outer s.sys.Smaller planets do not have enough gravity to hold on to H, He atmospheres.Outer Solar System = “Gas” Giants1. Solar wind blows H/He to outer solar system2. Outer solar system is COLD ENOUGH for gases like H, He, methane to CONDENSE (gas liquid). For accretion to occur, materials need to be liquid or solid.
6 Evidence to Support1. Sun is 99.9% of mass (b/c gravity pulls nebula to center) 2. Planets all orbit in same plane (b/c started off in spinning disk) 3. Planets orbit in same direction (b/c started off in spinning disk)
7 4. We’ve observed protoplanetary disks around other stars.
8 Evidence that Earth is 4.6 billion yrs. old Meteorites All meteorites (asteroids, space rocks, etc.) are the same age when radioactively dated: 4.6 billion yrs.Meteorites do not change (no volcanism, plate tectonics, weathering).We assume all objects formed at the same time.There are metals found in meteorites that can only be made during supernova explosions.Our solar system formed from a nebula produced by a supernova.