EASC 108 Lecture Notes - Lecture 7: Global Catastrophic Risk, Close Encounter, Oort Cloud

• School: Simon Fraser University
• Department: Earth Sciences
• Course: EASC 108
• Professor: Glyn Williams- Jones

Document Summary

Satellite: an object that orbits a planet (e. g. , our moon) Asteroid: a relatively small (> 1m) rocky object that orbits a star. Comet: a relatively small, icy object that orbits a star. Cratered, angular, rocky leftovers of planet formation. 150,000 in catalogs, prob over a million with diameter >1km. All asteroids in solar system would not add up to even 1 small terrestrial planet. Asteroid ida has a tiny moon named dactyl. Measure the orbit of asteroid"s moon gives us the asteroid"s mass. Mass and size give us asteroid"s density. Some are solid rock; others just piles of rubble. Most asteroids orbit in the asteroid belt between mars and jupiter. Orbits of near-earth asteroids cross earth"s orbit. Asteroids in orbital resonance with jupiter experience periodic nudges. Eventually, nudges move asteroids out of resonant orbits. Rocky planetesimals between mars and jupiter did not accrete. Jupiter"s gravity, through orbital resonances, messed up asteroid orbits.