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9/5/2012 To describe the process that created our solar system To describe the order that objects in the solar system were created and where the vast majority of the mass created Nebular Theory explains how the solar system formed Formation of our Solar System a) After the Big Bang explosion, there was only dust and gas left. b) Gravitational forces started to pull the dust and gas together to form a nebula. As the nebula grew, gravity increased and pulled in more gas and dust. c) The nebula started to rotate. rotate Increased gravity caused the nebula to contract or get smaller and more compact. d) The most compacted part of the nebula was in the center. This is where the sun started to form 4.6 billion years ago. ago. 98.5% of the nebular dust and gas went to building the sun. sun. What happened to the leftovers? • Due to the power of the gravitational forces, forces, 98.5% of the nebula formed the sun. • The remaining 1.5% was too far from the sun to be affected by gravity. This left a clear area between the sun and the leftovers. leftovers. • Planets, moon, asteroids, meteors, comets, etc. were formed from the left over materials 0.5 billion years after the sun. • Planets formed in the leftover area of dust of gases in a two step process. 1. Condensation: 2. Accretion: Condensation • We know from studying water, that condensation is when a gas is changed into a liquid because gas crosses its’ boiling point. point. •We see this happen as a cold sold warms up and water droplets form on the outside. • The leftover gases were very far away from the sun, causing cold temperatures, and forcing them to condense and form liquids. liquids 1 9/5/2012 (d) Different materials will condense at different temperatures: Rocky & metallic materials (iron, magnesium, and silicon) have low boiling points. The change first, under high temperatures because they are the closest to the sun. Eventually, the liquids will change into solids. Light materials (hydrogen and helium) have very low boiling points. They will not change because it does not get cold enough. They are the farthest from the sun. (e)Gravitational forces will compress the solid & liquid materials to form an early planet that is called: Planetesimal, planetoid, or a protoplanet Accretion • Gravitational forces develop in the protoplanets, which will start to pull in left over dust and gas • This process is called accretion or “clearing your neighborhood.” • Protoplanets grow by accretion. Accretion stops when there is no more dust or gas in the orbit. Once accretion is complete, the protoplanet becomes a planet. The birth of a solar system… 1. Gravitational forces form a nebula and it starts rotating 2. Sun forms in the middle of nebula 3. Condensation: Leftover gases turn into liquids, protoplanets start to form 4. Accretion: Gravity develops in protoplanets, adding leftover dust in the orbit 5. Planets form when the orbital path is clear of dirt! 2