Review for exam #2
Expect several questions from each of the following areas. Equations are compact ways
of delivering key concepts, we will not use them to do calculations.
Basic equations:
Thermal speed depends on mass at given temperature, but escape speed does not, so that's why
terrestrial planets can hold carbon dioxide, nitrogen, and oxygen, but not hydrogen.
Surface temperature of planets is determined by a radiative energy balance with absorbed sunlight.
The latter drops with distance like 1/d^2, the radiated energy depends on surface T like T^4, so
put them together: T depends on the inverse square root of distance.
I. The formation of the Sun and planets
-- the solar nebula
-- angular momentum = mvr
-- formation of a disk and planets
-- force balance by orbital vs. thermal motion: disk vs. star, angular momentum or pressure
-- onset of nuclear fusion
-- final state as quantum mechanical ground state
II. Planet formation
-- grain condensation
-- composition: icy comets, silicon-rich asteroids, hydrogen-rich giants
III. Meteors and their origins
-- falls and finds, rock and metal
-- comets: primitive rock and volatiles destroyed in atmosphere
-- asteroid belt: rocky, circular prograde orbits
, see what it looks like here
-- Kuiper belt: icy, circular prograde, comet formation zone, see it
here
-- Oort cloud: long-period comets, perturbed by large planets, passing stars
IV. Comet structure and orbits
-- nucleus, coma, tails (I and II)
-- nearly "parabolic" from Oort cloud, all directions
-- short-period from Kuiper belt, less elliptical, more likely to be prograde
-- all are bound to Sun, so members of the solar system
V. Buoyancy and differentiation
-- material with lower density than the fluid it is imbedded in will float
upward, and higher density will sink
-- floating objects displace their mass in water, sunk objects displace
their own volume, a principle discovered by Archimedes.
-- irony metals=8 g/cc, silicon-rich rocks=3 g/cc, water=1 g/cc
-- slow cooling allows crystals and differentiation
-- fast cooling inhibits differentiation, gives glasses
VI. Surface formation
-- regoliths
-- cratering
-- volcanism
-- plate tectonics
-- history of water
VII. The story of air and water
-- outgassing
-- what happens to water
-- what happens to carbon dioxide
-- what happens if water and carbon dioxide freeze out
-- how did we get free oxygen
VIII. Planetary temperatures
-- core temperature (planet size and cooling history)
-- surface temperature (distance and temperature of the Sun)
IX. Special Topics:
-- tides
-- the Cassini division and resonance
-- (gravitational interactions, slingshots and acceleration,
Lagrange points that move with planet orbit)