astronomy exam 2.docx - Solar system 4.6 billion years old flat and disk shaped formation asteroids and comets are leftover planetesimals that never

astronomy exam 2.docx - Solar system 4.6 billion years old...

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Solar system: 4.6 billion years old ; flat and disk shaped; formation ; asteroids and comets are leftover planetesimals that never accreted into planets Planets : orbit around sun, round, cleared the neighborhood around its orbit; orbit counterclockwise west to east; most rotate same direction Terrestial Planets : Mercury, Venus, Earth, Mars; close to sun, close together, solid, warm, smaller size and mass, high density, rock and metal (inner nebula was hot, only metals and rock could condense there), few moons, no rings Jovian Planets: Jupiter, Saturn, Uranus, Neptune; far from sun and eachother, large size and mass, low density, made of hydrogen, helium, and “ices” (outer nebula=cold, ices and rock and metal could condense), not solid, cold, many moons, all have rings Dwarf Planets: same characteristics as planets but cant clear neighborhood; very small, mostly ice, includes Pluto Asteroids : lots of craters, not round, rocky, airless, orbit sun, most are between Jupiter and mars, huge space between them Comets : three parts; nucleus, coma, tail made from melted ice when comet gets close to sun) ices/rock/dust, most orbit beyond Neptune, show tails when close to sun; tail points away from sun and becomes longest and brightest at perihelion Meteroids : small debris Kuiper Belt : thousands of small dark icy bodies, Pluto and Eris (same size as Pluto) come from there Solar Nebular theory : our solar system formed from a giant cloud of interstellar gas and dust; nebula=cloud; when it contracted —rotation rate increased, flattened into a disk, temp increased; protosun formed at the center using gas from the disk Conservation of angular momentum : as a rotating object contracts, its rate of rotation must increase (like ice skaters) Frost Line: a circle at a particular distance from the sun, beyond which the temp was low enough for ices to form; seperates the two types of planets; objects inside line form asteroids; outside line form comets Heavy bombardment : period where all left over planetesimals bombarded other objects in the late stages of solar system formation; lasted 800 million years Cosmic Water : earths water probably came from ice comets hitting earth Giant Impact Theory : earth collided with a large mars-like object and blew up lots of material into orbit and the core of it and earth formed one large core and the material orbited the earth forming the moon Age of solar system : when a rock forms, some atoms are radioactive and decay; use half-lives Different looks of Terrestials : all have core—has mantle (dense rock) in middle surrounded by crust Differentiation : materials separated by density; dense stuff sank to center; less dense stuff floated to surface; this is how “cores” were formed Processes Shape Terrestial surfaces (surface geology) : cratering (modified by erosion), erosion, tectonics (stretching or compressing of a planet’s crust), volcanoes (erase geological features and replaces it with rock and releases gases) Geological activity of a world :
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