11/17/2011 Ch. 27 Notes: Nebular Hypothesis • Objective: – To examine the evidence of the origin of our solar system. – Use reasoning skills to determine how the formation occurred. The Nebular Hypothesis • A rotating cloud of gas and dust condensed to form the sun and surrounding planets. • Solar Nebula: Rotating cloud of gas and dust that formed the solar system. http://www.networlddirectory.com/images/blogs/crab-nebula-552300.jpg • What caused the nebula in the first place? – The material from an old supernova (star explosion) gathers in a very large area in space. 1 11/17/2011 Steps to the Nebular Hypothesis • Step 1: Nebula starts to collapse – What causes the collapse? • Gravity within the nebula is just strong enough to keep the gases and dust hanging around. • A nearby supernova explosion sends shockwaves through the nebula. • Material is starting to collide and mass increases in areas of the nebula. • One area grows in mass and gravity the fastest pulling surrounding material toward it. Becomes the central point of gravitation focus. The Nebular Hypothesis • Step 2: Nebula develops a center point of rotating material and flattens like a disc. • Why is material revolving around a center point? – Increase in gravity at center pulls in more nebula material. • More material collides creating heat. • Material is packed tight (dense) creating pressure. • Why does the nebula flatten like a disc? – Force of rotation in the center moves all material in line with the center, moving like the center rotation. The Nebular Hypothesis • Compounding heat and pressure causes reactions with hydrogen gases. • Electromagnetic energy is released and a star is born. 2 11/17/2011 The Nebular Hypothesis • Step 3 (Formation of a Planetesimal): Chunks of smaller rocky material collide (irregular shape). – How does gravity change? • Step 4 (Growth of a Planetesimal): Gravity increases with size, attracting the surrounding smaller rocks, gases and dust. http://api.ning.com/files/IN49ap-JavmN3V8mtFNRHb5Znc53pK9HKcT9Rflu9MzkTLJggeRayi41mXI2nAZQ1a99XWzd-QzW52L1RpAUcG0aH1A-XBdI/SolarNebula.jpg The Nebular Hypothesis • Step 5 (Formation of a Protoplanet): Planetesimals begin to collide and join together through gravity becoming Protoplanets. (continually growing, but with a more regular, spherical shape). – How can the spherical shape maintain with these huge collision? The Nebular Hypothesis • Step 6 (Formation of a Planet): How is it different from the protoplanet? – The planet no longer deals with massive collisions. – Gravity is able to pull the material together tighter (more dense), which causes the size to shrink slightly smaller. – A smaller, but more organized and developed planet is formed. http://www.sciencedaily.com/images/2007/01/070108093817.jpg http://eps.berkeley.edu/cig/depaolo/eps102/lecture_images/Early_Earth.jpg 3 11/17/2011 The Nebular Hypothesis Model 4 .