AST 2002 Lecture Notes - Lecture 10: Thermostat, Terrestrial Planet, Earth Mass
Document Summary
Asteroids leave trails in long exposure images because of their orbital motion around the sun. Asteroids are rocky leftovers of planet formation. The largest is ceres, diameter 1000 km. There are 150,000 listed in catalogs, and probably over a million with diameter less than 1 km. Small asteroids are more common than large asteroids. All the asteroids in the solar system wouldn"t add up to even a small terrestrial planet. Asteroid orbits: most asteroids orbit in a belt between mars and jupiter, trojan asteroids follow jupiter"s orbit, orbits of near earth asteroids cross earth"s orbit. Orbital resonances: asteroids in orbital resonance with jupiter experience periodic nudges, eventually those nudges move asteroids out of resonant orbits, leaving gaps in the belt. Origin of asteroid belt: rocky planetesimals between mars and jupiter did not accrete into a planet, jupiter"s gravity, through influence of orbital resonances, stirred up asteroid orbits and prevented their accretion into a planet.
