# class02a - - rocks and metals. And the giant planets have...

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AST 309S The Solar System MWF 11-12 John Lacy RLM 16.332, M-F 12-12:30 471-1469 lacy@astro.as.utexas.edu Amanda Bayless Daniel Kagan RLM 16.312, Th 10-12 RLM 15.202A, W 3-5 471-3462 232-3923 baylessa@astro.as.utexas.edu kagan@astro.as.utexas.edu

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Terrestrial and Giant Planets radius mass mass/radius mass/radius 3 Mercury 0.38 R earth 0.05 M earth 0.13 0.91 Venus 0.95 R earth 0.82 M earth 0.86 0.96 Earth 1.00 R earth 1.00 M earth 1.00 1.00 Mars 0.53 R earth 0.11 M earth 0.21 0.74 Jupiter 11.0 R earth 318 M earth 28.9 0.24 Saturn 9.0 R earth 95 M earth 10.6 0.13 Uranus 3.9 R earth 14 M earth 3.6 0.24 Neptune 3.8 R earth 17 M earth 4.5 0.31
Why is mass/radius 3 important? Volume of a sphere = 4 π /3 R 3 So comparing mass/radius 3 is the same as comparing mass/volume, which is density. If two objects are made of the same stuff (and not squeezed too much) they will have the same density. Try it for two aluminum blocks. The fact that the terrestrial planets all have about the same density suggests that they have similar compositions

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Unformatted text preview: - rocks and metals. And the giant planets have similar compositions (but different from the terrestrial planets) molten ices and gases. Definitions Volume: how much space an object takes up you always multiply 3 numbers together to calculate volume: width x depth x height for a box width x depth x height for a triangular box 4 /3 radius x radius x radius for a sphere Mass: how much matter is in an object Weight: the force of gravity on an object two objects with the same mass will have the same weight on the Earth. Density: mass / volume density depends on the composition of an object, not how big it is. Reading for this week Chapter 1: A Tour of the Solar System For next Monday, read chapter 2: The Internal Structure of the Terrestrial Planets...
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## This note was uploaded on 07/13/2010 for the course AST 309 taught by Professor Johnlacy during the Spring '08 term at University of Texas at Austin.

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class02a - - rocks and metals. And the giant planets have...

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