Download 11/17/2011 1 Ch. 27 Notes: Nebular Hypothesis The Nebular

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Ch. 27 Notes: Nebular Hypothesis
• Objective:
– To examine the evidence of the origin of our solar
– Use reasoning skills to determine how the formation
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.
• What caused the nebula in the first place?
– The material from an old supernova (star
explosion) gathers in a very large area in space.
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
• 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.
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.
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
The Nebular Hypothesis Model