Astronomy Final Exam

Star 

• A large, glowing ball of gas that generates heat and light through nuclear fusion.

Planet

• A moderately  large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition 

Asteroid 

• A relatively small and rocky object that orbits a star

Comet

• A relatively small and icy object that orbits a star, has a tail of light

• Sun causes the tail of the comet 

• Takes a comet 100 years to be seen again 

  • Swings around the sun and flies farther than pluto

• Comets come from the Kuiper belt 

“Why we have seasons on earth” quiz

Galaxy

• A great island of stars in space, all held together by gravity and orbiting a common center

Seasons 

• At an average distance of 1AU = 150 million km

• With earth's axis tilted by 23.5 

  • (pointing to Polaris)

• And rotating in the same directions it orbits, counter-clockwise and viewed from above the North Pole 

• Orbit around the sun is not a circle but almost a circle 

• The orientation of the titles axis remains the sun same as the earth revolves around the sun  

Summer Solstice 

• Longest day of the year

  • 24hr day

Winter Solstice

• Shortest day/ longest night 

  • 24hr night

Equinox 

• Equal night and day 

  • 12hr day/12hr night

Global Warming

Emission Line Spectrum 

• A thin or low layer density cloud of gas emits light only at specific wavelengths that depend on its composition and temperature, producing a spectrum with bright emission lines 

Ozone layer

• Oxygen

•  This thin layer of protection 

Light 

• Light is a wave

  • Short Wave 

  • Gamma rays

    • Travels at the speed of light 

    • High energy

    • Hard to produce

  • X-rays 

    • Storms or in a hospital 

  • UV light

  • Visible light 

    • Blue to Red 

    • Rainbow

  • Infrared

    • Can not see

  • Microwave

  • Radio wave 

  • Long wave

  • The sun produces visible light and the moon reflects visible light 

  • Moon produces infrared light

  • All objects emit light of wavelength rhr depends on their temperature 

Global Warming 

• What warms the earth  

• How does the earth cool off

• Visible light from the sun inds on earth 

• The earth releases IR light (infrared light) into space 

Greenhouse gasses

• Blanket that traps IR light 

Emission Line Spectrum 

• A thin or low-density cloud of gas emits light only at specific wavelengths that depend on its composition and temperature, producing a spectrum with bright emission lines

Measuring the shift

• We generally measure the Doppler Effect from shifts in the wavelengths of spectral lines 

Atom 

• Number of proteins 

  • Proton is a charged particle 

• Different atoms have different numbers of protons 

Kepler's Law Exam (Star chart, extra credit)

Ecliptic Plate

• The path the sun follows in the sky 

Phases of the moon

• Full, waning, waxing, quarter, new 

• We see the side of the moon with light 

• Ignore shadows

Eclipse 

• Shadows of the earth and moon 

• Solar eclipse

  • The shadow from the moon is placed upon the earth 

  • New moon

• Lunar eclipse

  • The shadow of the earth is on the moon 

  • Full moon

Why don't we have an eclipse every new and full moon

• The moons orbit is tilted 5º to ecliptic plane

  • That's why eclipse are rare

• So we have about two eclipse seasons each year, with lunar eclipse at new moon and solar eclipse at full moon 

Why don't we ever see the back of the moon 

• The moon rotates at the same speed as the earth

  • 30 days to orbit 30 days to spin 

  • “Tidal locking”

• The moon moves away from earth very slowly 

• The “Holes” on the moon are from volcanoes and caves

How does the orientation of earth's axis change with time 

• Although the axis is fixed on human time it actually processes over about 26,000 years 

  • Poolaris won't always be the north star

  • Positions of equinoxes shift around orbit 

    • Spring equinox, once in Aries 

Was there once so mysterious about planetary motion in our sky?

• Planets usually slightly move eastward from night to night relative to the stars

• But sometimes hry go westward relative to the stars from a few weeks

  • Apparent retrograde motion 

Does mars go backwards in its orbit 

• Mars does not do backwards in its orbit 

  • Its has a flowers orbital speed

  • Greater orbit radius

  • Earth moves

Galileo Galilei

• Galileo was the first scientists to discover the moons of jupiter 

• First person to do experiments to understand nature

• First person to use a telescope to study the sky 

Kelpers law’s

• First Law

  • The orbit of each planet around the Sun is an ellipse with the sun at the focus 

  • Sun lies at one focus 

• Second law

  • A planet moves around its orbit, it sweeps out equal areas in equal times

  • Planet travels faster when it is nearer to the sun and slower when it's farther from the sun

• Third law

  • More distant planets orbit the Sun at slower average speeds, obeying the relationship 

  • P2=a3

  • P = orbital period in years

  • a= avg. distance from the sun in AU

Why do planets move the ways described in Kepler?

Issac Newton (1643-1717)

• Angular momentum conservation also explains why objects rotate faster as they shrink in radius 

How does gravity cause tides

• Moon's gravity pulls harder on the near side of earth than far side

• Difference in moon's gravitational pull stretches earth 

Wien’s Law

• All objects emit light 

Spectroscopy 

• What is the element that is making the light 

• Rainbows 

(Exam #2)

Telescopes

“A bucket for light!”

• Refracting telescope: 

  • focuses light lenses

    • Need to be very long, with large, heavy lenses

• Reflecting telescope: xf

  • focuses light with mirrors

    • Can have much greater diameters

    • Most modern telescopes

Radio Telescope

• A radio telescope is like a giant mirror that reflects radio waves to a focus

Atmosphere is trouble for all telescopes except for radio waves

IR & UV telescopes

• Infrared and ultraviolet light telescopes operate like visible light telescopes but need to be above the atmosphere to see all IR and UV wavelengths

Calm, High, Fark, Dry

• The best observing sites are atop remote mountains 

• Rapidly changing the shape of a telescope's mirror compensates from some of the effect of turbulence 

Resolution

• How much detail does the picture contain 

  • High definition = better 

• Pixel size = Wavelength/Diameter of telescope 

  • Small wavelength is better, big telescope is better 

Interferometry 

• Using an array of telescopes to act like a single large telescope 

  • A bunch of telescopes that act like a big telescope

• Involves breaking up the telescope into pieces

• Can only do it with radio waves because it does not care about the atmosphere

  • Could do in space but too expensive

• But if you were to do it in space it would work with anything

• Picture of a black hole 

  • Using radio wave

  • Black holes are not big

Adaptive optics 

• Change the shape of the telescope to compensate for the distortion of the atmosphere

James Webb Telescope

• Latest telescope 

• Planetary/galaxy birth 

• Best Infrared b/c in space = very cold

The Sun 

Nuclear Energy 

• E=MC2

• Einstein, 1905

• All mass has a lot of energy stored in it 

• Nuclear Potential Energy (core) . Luminosity ~ 10 billion years 

Chemical energy 

• Hydrogen + oxygen = H2O

• Surface of the sun is called the Photosphere

  • Relatively cold (4,000K)

  • Core is hot (10^7K)

Two types of nuclear energy: Fusion & Fission, e.g., both changing atoms so nuclear energy

Fusion 

• Putting together atoms

• What the sun and stars do

• 4H-> He+ gamma rays & neutrinos

  • Fusing Hydrogen together to make helium and it comes in gamma rays(light)

  • Nothing nuclear

• The fuel has to be very hot

• Small nuclei stick together to make a bigger one 

Fission 

• Breaking up atoms 

• Big nucleus splits into smaller pisces 

• What we do in power plants

• Atoms with a lot of protons

  • Uranium, plutonium 

  • Radioactive

Gravitational contraction 

• Provided energy that heated core as Sun was forming 

• Contraction stopped when fusion began

Chromosphere

• Not visible to the naked eye (except during solar eclipses)

• 20,000 K (hotter than the photosphere)

• Very Dynamic and active

Corona

• Outermost layer of the solar atmosphere

  • 1 million K

• Photosphere 

  • Outerlayer of the sun 

  • Visible surface of the Sun 

  • 6,000 K

  • Coldest place in the sun 

• Convection Zone

  • Boiling gas

    • “Lava lamp” “cooking Spaghetti”

  • Energy transported upward by rising hot gas

• Radiation Zone

  • Energy transported by protons 

• Core

  • Center of the sun

  • Only place hot enough to generate nuclear fusion 

  • Energy generated by nuclear fusion 

Fusion of Hydrogen - P-P reaction 

• Proton-proton reaction 

Overall reaction 

• The sun fuses hydrogen 

  • fuel

• Puts them together and makes helium 

• Then becomes a gamma ray and then a neutrino 

• Neutrinos created during fusion fly directly through the sun 

• Observations of these solar neutrinos can tell what what's in the core

  • 4H -> He + gamma rays + neutrinos

Gamma rays

• The energy comes from fusion 

• Inside the sun light is slow

  • Drunk light zone

  • Bouncing around to the surface of the sun

• By the time it reaches the surface it is no longer gamma rays 

  • Visible light 

Density 

• Density = mass/volume 

Solar Neutrino problem 

• Early searches for solar neutrinos failed to find the predicted number

• More recent observations find the right number of neutrinos, but hace changes form

  • In the sun neutrinos are faster than light 

  • Produced at the center 

  • Are not faster than light just phase through everything

Earth

• Has iron at the center

• Is mainly constructed of rock

• Has small percent of water 

Stars

• THe brightness of a star depends on both distance and luminosity

• Luminosity

  • How bright i the stat

  • Actual brightness of intuitive brightness

    • “Absolute magnitude”

  • L=4 pi R2T4

  • Brightness = (Size of star squared)(temperature of star)

• Apparent brightness

  • How bright it seems to us

    • apparent brightness + distance = luminosity

• Two reasons why a star is so bright

  • Closest to you

  • It is actually really bright far away

One star equals the bright of 1 million of the sun

Properties of Thermal Radiation

• Hotter objects emit more light per unit area at all frequencies

• Hotter objects emit photons with a higher regency

  • Red star is cold

    • O stars means hot

  • A blue star is hot

    • M stars red cold

How do we measure stellar masses 

• Eclipse 

• A orbit of a binary star system depends on strength of gravity 

Two types of star clusters 

• Open cluster 

  • Stars are everywhere 

    • O & M

    • All colors 

• Globular cluster 

  • Stars everywhere

    • No O stars

    • O stars blew up 

    • Red an yellow

Interstellar Reddening

• Stars viewed through the edges of the cloud look redder because dust blocks (shorter - wavelength) blue light more effectively than (longer-wavelength) red light 

• The longer the wavelength the easier it is to get through the pollution 

• Infrared light reveal stars on the other side of the cloud

Planet Detection Methods

• Eclipse method 

  • Transit method

  • Looking for shadows

    • Nest method

    • Bill borucki

• Doppler Method “Wobble method”

  • Is the star wobbling

    • If yes, than a planet makes it wobble 

    • Jupiter has the most gravity pulling the sun

Gravitational lensing

• Planets can make the start background glitch

  • Microlensing

• Gravity bends light (blackholes)

• Floating planets

Meteorites

• If a meteor survives and lands on earth's surface, it is known as a meteorite

  • Iron meteorites: composed about 90% of iron 

    • They are much more likely to survive atmospheric entry 

  • Stony meteorites: Usually made up of oxygen, iron, silicon, magnesium and other elements

  • Stony-iron meteorites: mixture of both 

Small particles: cosmic dust 

• Sometimes from comets, sometimes left over from the cosmic dust cloud from which the Solar system formed

• When an meteor is 50 meters or bigger is can pass through our atmosphere and do as much destruction as New York City

Collision of comet Shoemaker-Levy 9 with Jupiter, 1994 

• Comet discovered March 1993, after it was captured into orbit around jupiter

• In 21 separate pieces! Broke up due to Jupiter's tidal forces

• All 21 fragments hit Jupiter in one week in July 1994

Northern Lights 

• Magnets on the sun have little particles

• When the magnets break up the particles fly apart

  • Solar wind 

  • Reaches the earth 

• Earth has a magnetic field at the center of the earth 

• The particles from the earth fly to the poles of the earth

  • South and North pole

  • When they smack the pole they release a glow 

Earth Atmosphere 

• An atmosphere is a thin layer of gas bound to a planet by gravity 

• The velocity of gas particles can exceed the escape velocity of the smaller planets 

The Earth's Atmosphere

• 79.1% Nitrogen (O2)

• 20.9% Oxygen (O2)

• .093% Ar

• .035% CO2 (increasing)

• .1-3% water (variable)

How heavy is the gas?

• Light gases can escape easier

  • Hydrogen 

  • Helium

• Hydrogen from our atmosphere escaped and we have very little helium bc the gravity was too light to keep the hydrogen 

Temperature vs. Gravity

• Heavier gasses tend to stay closer to the surface than lighter gases 

Where did the atmosphere come from?

• Volcanic Activity 

  • Moon

    • No tectonic plates (only earth)

    • No active volcanoes

  • IO 

    • Moon of Jupiter 

    • Active volcanoes

Any place with active volcanoes

• Mars - not active

• Cooled down

Why is the earth hot inside?

• Radioactive

• Heat trapped from the formation of the earth 

Earth's Magnetic field

Interior of the Earth

• There is a solid core of iron, surrounded by a liquid iron core 

• High energy, charged particles from the Sun are diverted around the Earth by its magnetic Field

The CO2 cycle 

• Atmospheric Co2 dissolves in oceans

  • Acid rain falls in the ocean and acidifies the ocean

• Erosion carries silicates (sand) to oceans

• Silicates react with dissolved Co2 to form minerals (like limestone)

• Plate tectonic carries minerals to subduction zones

  • Plats force the minerals underground

• Geological activity eventually releases CO2 back into the atmosphere

  • Volcanoes

Exam question?

1. Why does star formation lead to the formation of planets as well?

Star formation leads to the formation of other planets because the dust and raw material from the formation of stars from past star explosions leads to leftover residue. The formation of a spinning star spits out dust and raw material collected to create a planet. Then the materials contract using the skater effect condensing. The spin flattens into a disk around star, and the disk creates planets 

2. Describe the meaning of planetary detection selection effects. In particular, what kind of planets is the Doppler or wobble method likely to detect? 

The Doppler or wobble method is said to detect stars with planets based on whether the star is wobbly or shifting position ever so slightly. This method will likely detect huge planets and their gravity large enough to move the star.

CO2: Earth's Thermostat 

• Co2 is a greenhouse gas, helping to make Earth habitable today

• The amount of CO2 in the atmosphere may have varies in the past to keep Earth comfortable 

Density and Albedo

• The concepts of density and albedo are useful in planetary studies 

• Density = mass/volume

  • Density of water is 1 gram per cubic cm

  • Density of rock is 3 grams per cubic cm

  • Density of lead is 8 grams per cubic cm

• The density of an object can give an indication of its composition 

Phases of Matter 

• Matter has three “phases”

• Solid 

  • Constant volume and constant shape

• Liquid 

  • Constant volume but variable shape

• Gas 

  • Variable volume and variable shape

Atmospheres 

• In general, a gas will expand to fill its container. In the case of planetary atmosphere, gravity is the container

  • The gas particles will have characteristic velocity depending on the temperature at the surface of the planet and on the nature of gas 

Where is carbon stored on Earth 

• Soil, vegetation, atmosphere, ocean layers, limestone, sediments and rocks 

Faint Young Sun Paradox

• Astrophysical models indicate that sun's brightness should have increased significantly over age of solar system 

• So why wasn't earth frozen earlier

Earth atmosphere 

• The Earth's atmosphere is useful in at least three ways:

  • It keeps the earth warmer than it would be otherwise

  • It keeps the harmful UV and X-ray radiation from reaching the ground

  • It allows us to breath 

Reasons to Explore Mars

• Mars is the closest planet to  earth that astronauts can explore

• About 4 billion years ago, mars seems to had a earth like climate, with rivers, lakes, and maybe oceans,

• Mars was warm and wet, life on earth

What are forces that shape the surface of Mars

• Impacts

• Volcanism

  • Largest volcano/mountain in solar system

  • Big enough to have volcanoes but small enough to not have enough gravity to bring it down 

• Tectonics

  • No motion of plates

• Erosion 

  • Wind, sandstorm

The earth has no place with a bunch of creators bc of the wind, rain, waves, lava, and more

Erosion 

• Ancient erosion shows evidence for flowing water in early history of Mars

• Drainage channels were caused by flowing water

• Liquid water cannot exist on mars now bc the atmospheric pressure is so low

Fundamental message 

• Mars was warmer and wet (like earth) when life arose on our planet - maybe it also originated on Mars

• Life on Mars, if it existed may left traces as fossil evidence in some of the sedimentary rocks

• If life evolved with the Changing Martian climate, it may still be thriving in the ricks and in the soil below the surface

• The existence of life in extreme environments on earth (antarctica, arid deserts) suggest that this is possible 

1. Terrestrial Planets

• Mercury 

• Venus

• Earth 

  • moon

• Mars

  • Phobos and Deimos

2. Giant planets 

• Jupitper

  • Many moons

• Saturn 

• Uranus

• Neptune 

3. Dwarf Planet

• Pluto

4. Comets 

• Kuiper belt

• Orbit cloud

Mars

• Contains an atmosphere of CO2

  • Very thin 

  • No protection from UV light 

• Impacts can remove the atmosphere or Solar winds 

• Mars has no protective magnetic field 

• NO tectonic plates

• Dead Volcanoes 

  • Tallest volcano in the solar system 

• Mars has cooled down 

• Water is permafrost 

  • Frozen water 

Did Mars have liquid water on the surface in the past?

• Blueberries 

  • Small rounded pebbles caused by water flow 

• Look at the surface of the ground

  • Ancient water channels on the surface 

  • Craters 

• Enormous dust storms

• Much Smaller than Earth 

Venus and Earth Twin Planets

• Similarities

  • Size

  • Density

  • Have atmosphere

  • Both have cores

• Differences

  • Venus has no moon

  • Venus has no water

  • Venus is very hot

  • Venus has no magnetic field

  • Venus’s atmosphere is pure CO2

When we studied with telescopes

• We find sulfuric acid rain in the clouds of Venus

• Surface is extremely hot and the atmosphere is really thick 

• The pressure on venus is the same as being in the ocean 3000 feet below sea level

• Could nor sustain the kind of life we have on earth 

Volcanism 

• There are many distinct volcanoes on Venus  

• About 80% of the surface is covered with relatively fresh lava plains

• There are unique volcano type on Venus, such as pancake domes

• Long lava channels indicate a very fluid lava flow 

Tectonism 

• Venus displays a different kind of tectonism from that of earth 

• Earth tectonic motions are largely horizontal 

• Venus tectonic motions are largely vertical, resulting in large circular features called “coronae”

Venus and Earth Diverge

• Life on earth after the planet formed, early microbes becan to sequester CO2 dissolves in the ocean in the form of hard parts

• As the microbes died they settles to the ocean bottom, forming layers off calcareous sediments in which the CO2 is still held

• Limestone and dolomite are examples of rocks made of shells and carbonates made by animals from CO2 in the ocean 

The Runaway greenhouse

• Early venus (4 billion years ago)

  • Moderate temperatures

  • Water ocean

  • CO2 dissolved in ocean, or chemically combines with rocks

• Then 

  • Sun brightened, boiling the oceans

  • More CO2 was somehow deposited in the atmosphere

Consequences

• Oceans began to evaporate, releasing CO2 into the atmosphere

• H2O in the atmosphere contributed to heating

• CO2 gas was released from surface rocks

• The atmosphere and surface heated up because the greenhouse effect became stronger

• Heating liberated still more CO2 and H2O from the ocean and rocks, and temperatures continued to rise

The Origin of the Moon 

• What does a theory of the moon's origin have to explain?

  • Why does the earth have a satellite (moon)?

  • The catering history

  • The low density of the moon compared to earth (3.3 compared to 5.5 g/cm^3)

  • Why does the moon have so little metal?

    • Made of solid rock. No CORE

  • The fact the moon was once much closer to earth than it is now

• THe melted Earth began to differentiate

• Metals sunk to the center, and lighter rocky materials floated to the top 

• This formed a core, a mantle, and a crust

How will you get a moon without a core?

• An object about the size of mars collided with Earth, blasting a large quantity of the mantle and crust into space

• Mantle and crust material depleted in metal because differentiation was in progress

• THe nearly molten Earth quickly “healed” from the impact event that ripped off a large piece of the mantle

• This is the Giant Impact theory of the origin of the Moon 

What is Earth's CO2 cycle and how can it compare to Mars and Venus? 

• Mars and Venus have no CO2 cycle 

Ages of Lunar rocks 

• Rocks from the cratered highlands are oldest, most greater than 4 billion years

• Volcanic lava rocks from the maria are younger at 3.2 to 3.9 billion years old

Terrestrial planets

• Low mass 

• High density 

• Slow rotators

• Few satellites

• Close to sun

• Thin atmosphere

• Weak or no magnetic field

Giant planets

• High mass

• Low density

• Rapid rotators

• Many satellites

• Far from sun

• Thick atmosphere

• Strong magnetic field

What is a moon 

• A moon is something that orbits the planet 

Regular and Irregular moons 

Regular moon:

• Nearly circular orbits

• Orbits in the equatorial plane

• Prograde motion 

Irregular Moons:

• HIgly elliptical orbits 

• Orbits inclined to the planets equatorial plane

• Prograde and retrograde motion 

Three Planetary Moons of special note

• Io, the volcanic moon of Jupiter

• Europa, the icy moon of jupiter

• Titan, Saturns moon with a dense atmosphere

Io

• Slightly Larger than earth moon 

• Density 3.53 g/cm^3

• Thin silicate crust with no water

• Iron-rich core

• Molten silicate interior

• No impact craters= very young

• A volcanic caldera and an active eruption by the Galileo spacecraft

• The yellow color is due to sulfur the black features are lava lakes

Why is Io hot inside

• Io is pulled by the gravity of Europa and Ganymede, plus Jupiter

• Slightly elliptical orbit

• Jupiter keeps trying to make the orbit more circular

• The gravity pull causes Io to bend and flex. This flexing produces heat that keeps the interior molten 

Europa

• Broken and tilted icebergs floating in a frozen sea

• No impact craters. Its icy surface shows intricate network of crossing cracks, similar to cracks in the Artic ice packs on Earth 

• There is very to little vertical relief (no mountains of deep valleys)

• Very young surface

• Heated by gravitational effects of Ganymede and Jupiter (like Io), therefore it has an interior layer (“mantle”) of liquid water

Titan: Largest Moon in the Solayer System 

• Orbit period around saturn is 16 days

• Thic atmosphere mainly made of Nitrogen with small amount of methane 

• Which is hydrocarbon 

• Many other hydrocarbons also present

• Colder, but it has a greenhouse effect that warms the atmosphere

• The atmosphere is nearly opaque with organic smog, produced by sunlight acting on methane and nitrogen 

• We can see the surface indisticly at certain wavelengths where the atmosphere is partly transparent 

Roche Zone 

• if the particles are too close to the planet they disrupt the groth of the particles 

  • tides

• If the rings are inside of the zone you cannot grow moons

• If you are outside then the rings can become moons

If one were to remove all of the gases of helium and hydrogen from jupiter there is a solid rocky core with liquid ices in the middle. Almost identical to the sun without the core. The core of Jupiter is approximately 10 earths. This incidates that the rocky earth core was made first. As the core became to form it became a vacuum sucking around the suround gasses. With enough gravity to condense leading into the giant plaet Jupiter. The same goes for the other Giant planets except that the cores are not able to absorb as much gas from their surroundings. 

Discovery of Pluto 

• Calculations indicated thay neptunes orbit was being perturbed => another planet beyond neptune 

• Found in 1930 by Clyde 

• Orbit of Pulot is tilted 17 degrees tilted and elongated

  • Possible that pluto gets closer to the sun than neptune sometimes

• Not possible for pluto and neptune to collide

Pluto and Charon

• Smaller mass ratio than any planeet/moon, same density. 

• Both objects tidally locked

• Binary orbit gave precise mass estimates of both

• Rare eclipses in 1985-1991 gave diameters from timming measurements. Then could work out precise densities of Jupiter

• r, Saturn, Uranus & Neptune – the giant planets
  a. Composition: J& S like the Sun – mostly hydrogen
  U & N intermediate between gas giants and rocky planets
  b. General properties: clouds cover entire planets, rotation determined by measuring
  magnetic field tied to core for J and S and just above the core for U and N – rotation
  period of ~ 10 (J and S) and ~ 20 hours (U and N). J, S, and N slightly tipped; Uranus
  retrograde (like Venus) and rotating on its side.
  c. Differentiated interiors: molecular (gaseous) hydrogen, metallic hydrogen (J and S only),
  ``ice’’ and rock.
  d. You should have a general feel for the relative sizes, masses and densities o f the giant
  planets compared to the terrestrial planets.
  2. Moons, rings and Pluto
  a. Moons: regular, going around their planets in the same direction as the planets go
  around the sun; and captured irregulars, orbiting in the opposite direction (kind of like
  driving on the wrong side of the road).
  b. General properties of the satellite’s of Jupiter: Callisto, Ganymede, Europa and Io.
  Tidal heating of Io and Europa.
  c. Saturn’s biggest satellite: Titan. Only satellite with a thick atmosphere.
  d. Neptune’s biggest satellite: retrograde Triton.
  e. Rings: form from broken small moons; material can’t reassemble into a small moon
  because it is inside the Roche lobe or tidal limit.
  f. Pluto general properties and similarity to Triton. Pluto is due to be studied up close for
  the first time by the Horizons mission. Charon is the largest satellite relative to its
  parent planet. Pluto is a KBO (Kuiper Belt Object).
  g. You should have an understanding in the general ways that the satellites of the outer
  planets were formed (or captured) compared to our moon.
  3. Comets and Asteroids
  a. 75% of asteroids reside in ``asteroid belt’’ between Mars and Jupiter, about 40, 000 are
  known.
  b. Comets come from the Oort cloud 50,000 AU away; short period comets come from
  the Kuiper belt, just outside Pluto’s orbit; all comets eventually are flung out of the
  solar system or impact a planet or the Sun, e.g., comet Shoemaker-Levy.
  c. The giant impact that wiped out the dinosaurs is not a unique event.
  4. Our picture of Solar System formation
  a. The sun accumulated material through a thin rotating disk.
  b. Solids condense out of the solar nebula; rocky material is left near the Sun, ices
  survive farther out. ``Chemical Condensation’’ sequence.
  c. Planetesimals grow into protoplanets, continue being impacted, large planets attract
  gas
  d. Once cooled off, planets undergo individual geologic and atmospheric evolutions
  e. New ``Extrasolar Planets’’ – they look pretty different from the Solar System!
  Selection effects?