study guide 2

study guide 2 - Test #2 - pink half-sheet - #2 Pencil -...

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Test #2 - pink half-sheet - #2 Pencil - YOUR ID What was the solar nebula? The Solar Nebula -The nebular theory holds that our solar system formed out of a nebula which collapsed under its own gravity -Observational evidence -We observe stars in the process of forming today -they are always found within interstellar clouds of gas Solar Nebula- name given to the cloud of gas from which our own Solar System formed How did gravitational collapse affect the Solar nebula? Gravitational Collapse -The solar nebular was initially somewhat spherical and a few light years in diameter -very cold -rotating slightly -It was given a “push” by some event. -perhaps the shock wave from a nearby supernova -As the nebula shrank, gravity increased, causing collapse -As the nebula “falls” inward, gravitational potential energy is converted to heat -Conservation of Energy -As the nebula’s radius decreases, it rotates faster -Conservation of Angular Momentum Flattening of the Solar Nebula -Their random velocities average out into the nebula’s direction of rotation -The spinning nebula assumes the shape of a disk What are the orderly motions of the planets? Orderly Motions in the Solar System -The sun formed in the very center of the nebula -Temperature and density were high enough to nuclear fusion reactions to begin -The planets formed in the rest of the disk -This would explain the following: -All planets lie along one plane (in the disk) -all planets orbit in one direction (the spin direction of the disk) -The sun rotates in the same direction -The planets would tend to rotate in this same direction -most moons orbit in this direction -most planetary orbits are near circular (collisions in the disk) What produced the orderly motion we observe in the Solar System today? Building the Planets
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-Condensation – elements and compounds began to condense (i.e. solidify) out of the nebula depending on temperature -So only rocks and metals condensed within 3.5 AU of the sun, the so called frost line -Hydrogen compounds (ices) condensed beyond the frost line Things start out small -Grains of dust stick together -The particles form planetesimals -the planetesimals accrete together to form planets -Each gas (Jovian) planet formed its own “miniature” solar nebula -Moons formed out of the disk -Comets and asteroids are leftover planetesmials -The solar wind cleared the leftover gas, but not the leftover planetesimals -Asteroids are rocky because they formed insisd the frostline -Comets are icy because they formed outside the frostline How do we explain the exceptions to the rules? Exceptions to the Rules
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study guide 2 - Test #2 - pink half-sheet - #2 Pencil -...

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