Lecture 10/16

Two Major types of Planets

• Terrestrial - rocky w/ iron cores, few moons, close to sun
• Jovian - planet gaseous, lighter elements, many moons, far from sun*
• *not necessarily true for other planetary systems
• Uranus & Neptune are Ice Giants

Moons are natural Satellites

• All planets have moons, except mercury and venus
• outer planter have more moons than the inner planets
• seven satellites are almost as large as the inner planets
• ***Moon (very large) & Triton(orbits clockwise & large inclination) are the odd balls of the big satellites***

asteroids

• 500,000 + rocky objects mostly in the orbit of jupiter
• most orbit the Sun at distances of 2 to 3.5 AU in the asteroid belt
• Ceres, the first asteroid discovered, is now considered a dwarf planet

Trans-neptunian objects

• 1,000+ small objects orbiting beyond orbit of neptune
• the largest of these are known as dwarf planets
• Includes: pluto, Eris, Charon, Makemake, Haumea, etc.
• orbit the sun just the same (direction) as planets
• Most orbit the Kuiper belt at 30 AU - 50 AU

Comets

• periodic or long period
• periodic - (P < 200 years)
• orbit fits into keiper belt
• long period - one time visitors
• large eccentricity
• random orbital direction
• become "fuzzy" objects close to the sun ( d < 3 AU)
• can have more than one tail

Earth - the Water Planet

• third "rock" from the sun
• terrestrial planet
• 3/4 of surface is covered with water
• most important requirement for light is the right solvent with the right properties (water)
• water is densest at 4 degrees C
• good solvent (dipole)
• high heat capacity (insulator)

Earth in NUmbers

• raduis: 6353 Km polar, 6384km equatorial
• rotation period: 23 h, 56m, 4s
• density: 5.514 g/cm^3 (water 1 g/cm^3)
• Mass 5.98 x 10^24 kg
• S=m/v
• g=G*(M/r^2)=G*(s*v/r^2)
• Atmospheric pressure at surface 1 bar (29.52" of mercury)
• Atmospheric composition: see lecture slides
• crust -mostly basalt and granite

differentiation

• separation of different density materials, hes to be in fluid state.
• driven by gravity
• look at lecture slides

seismic waves

• earthquakes cause two types of waves:
• P-waves are longitudinal waves, like pushing a spring in and out - primary waves
• S -waves are transverse waves, like shaking a rope up and down - secondary waves

waves as earth probes

• paths curve gradually where there are gradual changes in density and composition
• sharp bends occur only at an abrupt change from one kind of material to another
• the speed of the waves depend on the density, we can model the earthquake propagation
• the outer core is liquid, mantle is liquid when pressed slowly
• the are points where waves will either bend or lo longer pass through
• look at lecture slides for images

structure

• rigid crust - granite and basalt