Enceladus A icy moon of Saturn Credit Cassini Imaging Team SSI JPL ESA NASA Course Announcements Quiz 3 will be on Friday 14 Oct Will cover chapters 5 and 6 Some hints today Assignments Reading Assignments No new reading Parallel Lectures No new episodes Mastering Astronomy Chapter 6 Homework Due Thursday 13 Oct at 11 59 PM EDT Pursuit of Artificial Intelligence Life Results from Notecard Q Comment Original I Robot is a series of 9 short stories by Isaac Asimov N 202 Asimov s Laws of Robotics Quiz 3 Hints Quiz 3 will cover Chapter 5 and 6 Know the different parts of the Solar System and roughly how far away each is from the Sun Terrestrial planets Asteroid Belt Gas Giant Planets Kuiper Belt Oort Cloud Know what Nebular Theory is and how it goes from a general nebula in outer space to the Solar Nebula How does this explain the orbital direction rotational direction and flat disk like shape of the Solar System Adding to above Know that Nebular Theory explains the structure of the Solar System and that Condensation Theory topic for today explains the chemical density gradient of the Solar System Be able to list the planets in order Example question Saturn is the planet from the Sun Quiz 3 Hints Quiz 3 will cover Chapter 5 and 6 Know the different parts of the Solar System and roughly how far away each is from the Sun Terrestrial planets Asteroid Belt Gas Giant Planets Kuiper Belt Oort Cloud Know what Nebular Theory is and how it goes from a general nebula in outer space to the Solar Nebula How does this explain the orbital direction rotational direction and flat disk like shape of the Solar System Adding to above Know that Nebular Theory explains the structure of the Solar System and that Condensation Theory topic for today explains the chemical density gradient of the Solar System Be able to list the planets in order Example question Saturn is the sixth planet from the Sun Quiz 3 Hints Quiz 3 will cover Chapter 5 and 6 Know the different parts of the Solar System and roughly how far away each is from the Sun Terrestrial planets Asteroid Belt Gas Giant Planets Kuiper Belt Oort Cloud Know what Nebular Theory is and how it goes from a general nebula in outer space to the Solar Nebula How does this explain the orbital direction rotational direction and flat disk like shape of the Solar System Adding to above Know that Nebular Theory explains the structure of the Solar System and that Condensation Theory topic for today explains the chemical density gradient of the Solar System Formation Environments in Context Visible Light ESA HST ESO Alma ESA HST Visible Light Radio Image The Big Question Where does the stuff to build planets come from Where do we get the solid materials that will build our planets Evidence suggests that nearly all the dust inherited from the nebular cloud of gas and dust is vaporized turned into a gas in the collapse to a disk process Not much solid material so how do we get it back and can that process explain the compositional and density gradient Condensation Theory Compositional Density Gradient As distance away from the Sun increases we see the see the same building block materials but keep adding new ones as we go further out How can we explain this Beyond here we start to see WATER ICE Metal Rock Ices Exotic Ices Metal Rock Ices Metal Rock Beyond here we start to see WATER ICE Metal Rock Gas Low Density Material Metal Rock Ices Metal Rock Ices Exotic Ices Gas High Density Material High Density Material Low Density Material The Early Solar Nebula Things get hot when you compress them The key is that the early Solar Nebula had a temperature gradient Inner Very hot 1500 2000 K near the protosun Inner Middle Moderate 273 K around 3 5 AU away or so Outer Cold about 100 273 K further out to about 30 AU Far Outer Very cold 100 K in the outer regions 30 AU This temperature gradient in the disk controlled what solid material could form out of the gas i e condense This temperature gradient controls what solids will condense out at a given distance Water can condense when cold enough The so called ICE LINE Condensation Theory Environment must be colder than condensation temperature in order to form that type of solid grain The Ice Line Condensed materials solids are what is available to form planets Condensation Theory Vo l ati le Re fra cto ry Based on the condensation temperatures of various materials i e a Condensation Sequence Temp must be below this to condense Oxides and Metals Fe Silicates Si O Al Mg Fe Hydrated silicates add water Carbonaceous materials C Ices Water Ammonia Methane Nitrogen Gas Hydrogen and Helium 1700 K 1200 K 700 K 500 K 273 K Deceasing 100 K Condensation 45 K Temperature 30 K Uncondensed The Story of Planet Building Nebular Theory Condensation Theory Now we have solid materials to build planets out of and we understand that we have more available materials as we increase in distance Proto Sun until a certain point where we start running out of material Metal Metal Rock Hot Build Terrestrial Planets Metal Rock High T Ices e g water Organics Warm Cool Build Gas Giant Cores the gas comes due to higher mass Metal Density drops so Rock can t really form Ices large things Organics Exotic Ices Low T Ices Cold Build Small Icy Worlds KBOs Story of Planet Building The Planet Building Process 1 Condensation of solids according to the condensation sequence function of temperature Chemically you will form about 2 grains of icy material for every 1 grain of rocky material Inner SS Metal and Rock grains available Middle SS Metal Rock Organics and High T ices Outer SS Metal Rock Organics High and Low T ices 2 Solid planet material formed from accretion clumping together of dust grains in the protostellar cloud video More material further out and more volume so outer planets can grow much much larger Accretion of grains into larger masses Story of Planet Building The Planet Building Process 3 The collections of solid grains grow through cm to m to km and eventuall 10s of kms in size These small planet like precursors are called planetesimals and they start to attract each other gravitationally when about 10 100 km in size Many of these small km to 100 km bodies still exist today in the Asteroid Belt and Kuiper Belt Story of Planet Building The Planet Building Process 4 Planetesimals grow very rapidly at this step through accretion as they run into each other When they reach a near planetary size they are called protoplanets 100s 1000 km and begin to
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