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Not a Planet!

Not a Planet!. The Sun and Planets to Scale. Planet definition: A celestial body that: (a) is in orbit around the Sun (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a nearly spherical shape; and

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Not a Planet!

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  1. Not a Planet!

  2. The Sun and Planets to Scale

  3. Planet definition: • A celestial body that: • (a) is in orbit around the Sun • (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a nearly spherical shape; and • (c) has cleared the neighborhood around its orbit; • If only (a) and (b) are met, it is a “dwarf planet”

  4. Terrestrial PlanetsJovian Planets - close to sun - far from sun - small - large - rocky composition - gaseous

  5. Terrestrial PlanetsJovian Planets - few moons - many moons - slow rotators - fast rotators - weak magnetic fields - strong magnetic fields - no rings - rings

  6. Composition Terrestrial PlanetsJovian Planets - silicon - oxygen - hydrogen - carbon - helium - nitrogen - carbon - argon - nitrogen - iron - oxygen - nickel - sulfur - etc. - etc. 95%

  7. The Formation of the Solar System

  8. The Solar Nebula • - Gas (99%) & Dust (1%) • - Gas- Hydrogen (90%), Helium (8%), C, N, O, etc • - Dust- Carbon Grains and ices (water, methane, ammonia)

  9. A Likely Formation Theory for Our Solar System 1. Occurred about 4.6 billion years ago 2. Collapse of Solar Nebula initiated by: a. chance mutual gravitation (not likely) b. gravity disturbance of a passing star c. collision with another nebula d. shockwave from nearby supernova

  10. 3. Contraction of Solar Nebula causes: a. heating in center (protosun) b. faster rotation (Conservation of angular momentum) ===> flattening c. lighter elements and compounds (H, He, methane, ammonia, etc.) driven by heat to outer solar system.

  11. 4. Terrestrial planets: a. dust grains collide and accrete, forming planetesimals ( diameter ~ 10 km) b. planetesimals collide with each other, forming protoplanets in about 100 million years. c. protoplanets cool over time. Solid surface ==> “planet”

  12. 5. Jovian planets (concurrent with Terrestrial planets): a. initial accretion creates ice (water, methane, ammonia) and rock core b. core “sweeps up” gravitationally H and He c. heated core releases vaporized ices ==> earth-sized rocky core with a large gas envelope of H, He, ammonia, methane, water vapor, etc. d. Jovian moons end up with rocky cores also, but with shells of ices of ammonia, methane, water

  13. 6. Protosun’s core temperature reaches 10 million K a. onset of thermonuclear fusion of Hydrogen to Helium in core b. Sun now a Main-Sequence star.

  14. Proto-planetary Disks in the Orion Nebula

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