EDWARD'S LECTURE NOTES:
More notes at http://tanguay.info/learntracker
C O U R S E 
Highlights of Modern Astronomy
Adam Frank, University of Rochester
https://www.coursera.org/learn/astronomy
C O U R S E   L E C T U R E 
Comparative Planetology
Notes taken on January 5, 2016 by Edward Tanguay
comparative planetology
we see a remarkable variation of planets even in our own solar system
various forces drive the formation and development of planets, enables us to understand
habitability
does the planet have moons, are those moons habitable
each planet has a different story
each planet has certain possibilities for a home for life
long term
short term
our planetary system
three flavors of planets
1. terrestrial
rocky planets
the inner planets closest to the Sun
Mercury, Venus, Earth, and Mars
have a solid planetary surface, making them substantially different from the larger giant planets, which are composed mostly of some combination of hydrogen, helium, and water existing in various physical states
a central metallic core, mostly iron, with a surrounding silicate mantle
silicates comprise the majority of Earth's crust, as well as the other terrestrial planets, rocky moons, and asteroids
sand, common cement, and thousands of minerals are examples of silicates
have canyons, craters, mountains, volcanoes, and other surface structures, depending on the presence of water and tectonic activity
2. gas giants
Jupiter, Saturn
enormous
may or may not be a rocky core
built of a simple material, although in different states
composed mainly of hydrogen and helium
3. ice giant
Uranus, Neptune
large compared to the Earth
much of their material is locked up in ices
a mix of gases and ices in different states
consist of only about 20% hydrogen and helium in mass, as opposed to the gas giants (Jupiter and Saturn), which are both more than 90% hydrogen and helium in mass
outermost portion of their hydrogen atmosphere is characterized by many layers of visible clouds that are mostly composed of water and ammonia
moons
all planets in our solar system have moons except for Mercury and Venus
Mercury = 0
Venus = 0
Earth = 1
Mars = 2
Jupiter = 16
Saturn = 19
Neptune = 8
Uranus = 15
debris
material left over from the development of the solar system
dwarf planets
Pluto
Xena
2005 FY9
2003 EL61
Sedna
Quaoar
quite spherical, but not as large as a planet
they have not done much in terms of their gravity vacuum up material around them
one of the characteristics of a planet
the ability of the object's gravity to clear out a gap around it
asteroids
planetesimal
small enough that they did not become spherical
not enough gravity to take their mass and crush it down under its own weight
essentially these are large, floating rocks
comets
debris left over from the solar system
tends to be much more frozen water in these than in, e.g. asteroids
a mix of frozen water and rocks
"slushy mud balls"
structure of the solar system
they are all orbiting in the same plane
all the planets and most of the construction debris is orbiting in a disc
some of the planets have slight inclinations but pretty much all are aligned in a single disc of rotation
the planets are pretty much all spinning in the same direction
also spinning in the same direction as the Sun is spinning
belts of debris
1. Asteroid Belt
2. Kuiper Belt
beyond the orbit of Neptune
storage area for comets
3. Oort Cloud
storage area for comets