PHYSICS 20A Lecture Notes - Lecture 17: Roche Limit, Exoplanet, Planetary System
Document Summary
Physics 20a lecture 17 rings & exoplanets. Material of the rings/disks inside the roche limit cannot clump together: therefore they will not form single satellites, planet"s tidal forces are too strong. Material ejected from impacts on the moons settle into the rings. Rings are temporary: they dissipate over time. Many individual ringlets: ~100,000, each are 20m thick, reflective of sunlight. He thought they were moons: made of mostly ice water, organic compounds & carbon. Ranging in sizes from pebbles to boulders. Shepherd moons: pandora & prometheus keep their gaps clean. Discovered by voyager, an old space probe. They don"t really reflect sunlight: you can"t see them, composed of sooty dust particles. Main ring: inner ring, made of dust from moons adrastea and metis. Gossamer rings: outer rings, made of dust from moons amalthea and thebe. They brighten and dip as they pass a star: but they fade immediately, they are very thin.
