Comets spend a very small percentage of one period in the inner solar system

Comets spend a very small percentage of one period in

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Comets spend a very small percentage of one period in the inner solar system (kepler’s second law) Short Period Comets- may come from the oort cloud and have been deflected into closer oribits. Jets of sublimated gas can deflect comets in their orbits Demise of Comets Two comets for example, met their demise, by 1. Colliding with Jupiter, and 2. by getting to close to the sun and fragmenting. o Asteroids Rock and/or metal, mostly between mars and Jupiter. Properties Small compared to planets or large satelities. Largest one, Ceres, is only 1000 km across. Mostly not sphereical (except for Ceres) Shaped more like potatoes Gravity not strong enough to compress rocky material. Some are collections of “gravel”. Orbital Properties of Asteroids Asteroids orbits are more elliptical and inclined than planetary orbits. Most are in the asteroid belt. Some share jupiters orbit. – two pass infront and behind it- the LaGrange points. Trojan asteroids cross earth’s orbit The Asteroid Belt Orbit resonances with Jupiter created gaps as in Saturn’s rings, known as Kirkwood Gaps. Resonances explain why no planet formed in the asteroid belt. Jupiter disrupted formation and scattered most planetesimals in the region. Measuring Asteroids Diameter- from reflectivity and distance Mass- effect on a passing spacecraft or a moon Density- mass / by volume 15
Shapes- measure the asteroid’s changes in the brightness as it rotates. We can bounce radar signals off of near-earth asteroids. Asteroid Compoistion- 3 major groups C-Type- Carbon rich, very dark o Outer regions of asteroid belt S-Type- Rocky, brighter o Inner regions of asteroid belt M-Type- Metallic o Rocks Falling from the Sky Meteor Shooting star. Most particles are the size of a pea. Meterorites Survived fall to earth Caused brighter meteor a fireball Higher metal content than terrestrial rocks Contains indium and isotopes not found in terrestrial rocks. Types of Meteorites- Primitive- stony or carbon rich Processed- metallic or rocky. Origins of Meteorites Primitive- o formed directly from solar nebula o stony formed inside frost line o carbon rich formed outside the first line, where carbon compounds condense. Processed o came large objects in the inner solar system. o Metallic ones are fragments of cores of asteroids shattered in collisions o Rocky ones were chipped off surfaces of asteroids, mars, and the moon impacts. Meteor Showers When earth passes through comet debris You can see as many as one meteor per minute Shower dates correspond to when earth passes a given comet’s orbit Meteors appear to shoot from the point directly ahead in the direction that earth is moving/ named for the constellation from which the meteors appear to emanate.

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