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General Properties of the Solar System … continued

General Properties of the Solar System … continued. Announcements. Reading for next class 8-4, 8-5, 8-6 (pp. 171-180) Quiz today Closed book, closed note, no electronic devices (like it will be for the exam) First Exam Next Thursday (2/15)

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General Properties of the Solar System … continued

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  1. General Properties of the Solar System … continued Solar System 2/8/07

  2. Announcements • Reading for next class • 8-4, 8-5, 8-6 (pp. 171-180) • Quiz today • Closed book, closed note, no electronic devices (like it will be for the exam) • First Exam Next Thursday (2/15) • Brief review and discussion of the exam format on Tuesday • Come prepared with questions • Make use of study groups, instructor and TA office hours to help you prepare Solar System 2/8/07

  3. Next Week’s Preceptor-led Study Group • Monday – 10:30AM-12:00PM Preceptors: Chris Dockins, Maggie Jahn, Katie Landon, and Jared Mosley Room 330 of Kuiper Space Sciences • We encourage you to attend and study for the exam with a group of students from the class Solar System 2/8/07

  4. Solar-system inventory continued…The Sun • Most massive object in the solar system • Formed at about the same time as all of the planets, and from the same material • The source of energy that keeps is shining for billions of years is thermonuclear fusion Solar System 2/8/07

  5. Solar-system inventory continued…The Solar Wind • The solar corona is in a constant state of expansion and continues off into space, creating the Solar Wind • The Solar Wind is a plasma – the 4th state of matter (solid, liquid, and gas are the other 3) • Its existence was predicted based on observations of comet tails (the blue ion tail in the picture is directed along the solar wind) Solar System 2/8/07

  6. Solar-system inventory continued…Small chunks of rock and ice also orbit the Sun • Asteroids are small, rocky objects, while comets and Kuiper-belt objects are made of dirty ice (or icy dirt?) • All are remnants left over from the formation of the planets • Some of them contain the primordial material from which the solar system is made Solar System 2/8/07

  7. Kuiper Belt Objects • Beyond the orbit of Neptune • Distributed loosely along the ecliptic plane • Pluto is a large KBO • Asteroid belt • Between the orbits of Mars and Jupiter • Probable origin of Near-Earth objects Solar System 2/8/07

  8. Solar-system inventory continued…The outer reaches of the Solar System • The Heliosphere • The cavern carved out of the interstellar gas by the solar wind • The Oort Cloud • contains billions of comet nuclei in a spherical distribution that extends out to 50,000 AU from the Sun • Intermediate period and long-period comets are thought to originate in the Oort cloud • As yet no objects in the Oort cloud have been detected directly Solar System 2/8/07

  9. Structure of a Terrestrial Planet • Metallic core in center • Rocky mantle • Crust of some sort? • All are differentiated • But the proportions of the core, mantle, crust, differ  Look up its definition ! Solar System 2/8/07

  10. Will a planet have active volcanoes? • Requires Heat • After the planets formed, they were very hot • Big planets cool slower • Small planets cool more rapidly • Big terrestrial planets are active longer • Fewer craters • More likely to have active volcanoes • Earth and Venus for example – both of these worlds also have very few visible craters Solar System 2/8/07

  11. Planetary Magnetic Fields • Another important tool for “probing” the interior of a planet • Magnetic fields of terrestrial planets are produced by metals such as iron in the liquid state (molten core) and in motion (dynamo action) – moving electrically conducting material • The stronger fields of the Jovian planets are generated by liquid metallic hydrogen or by water with ionized molecules dissolved in it • Earth, Mercury, and all Gas Giants have magnetic fields – Mars and Venus do not Solar System 2/8/07

  12. Impact Cratering • When an asteroid or comet strikes the surface of a terrestrial planet or moon, the result is an impact crater • Geologic activity renews the surface and erases craters, so a terrestrial world with extensive cratering has an old surface and little or no geologic activity • Because geological activity is powered by internal heat, and smaller worlds lose heat less rapidly than larger ones … as a loose general rule… the smaller a world is, the more heavily cratered it will be Solar System 2/8/07

  13. Will a planet have an atmosphere? • Requires a gas • The gas must be cool enough to not escape • The planet must have enough gravity to prevent the escape of gasses • Big, cool, planets are more likely to have atmosphere Solar System 2/8/07

  14. To understand the retention of an atmosphere, we need to understand the motion of particles in a gas • Kinetic Energy associated with an object of massmin motion with a speedv • SI unit of energy • Joule (kg m2/s2) Solar System 2/8/07

  15. Kinetic Energy and Temperature • Kinetic Energy of a gas with temperature T k = Boltzmann constant = 1.38 x 10-23 J/K Solar System 2/8/07

  16. Average speed of atoms in a gas • Equate kinetic energy of motion to that of the gas at a given temperature, and solve for the velocity, v This is the AVERAGE SPEED of atoms in a gas having a temperature T Solar System 2/8/07

  17. To understand whether the gas is gravitationally bound to a planet, we need to understand the concept of Escape velocity • The speed that an object must have in order to escape the pull of gravity of a planet of mass M and radius R is: Solar System 2/8/07

  18. As a loose, general rule of thumb: • A Planet can retain a gas if the escape speed is at least 6 times greater than the average speed of molecules in the gas Solar System 2/8/07

  19. Table Solar System 2/8/07

  20. The diversity of the solar system is a resultof its origin and evolution • The planets, satellites, comets, asteroids, and the Sun itself formed from the same cloud of interstellar gas and dust • This material came from cosmic processes that took place within stars that died long before our solar system was formed • Different planets formed in different environments depending largely on their distance from the Sun Solar System 2/8/07

  21. How Old is the Solar System ? • How can we determine this ? • Radioactive dating • Need to find the right material to date ! • Because of plate tectonics and geological activity, Earth rocks are not a good indicator of the age of the Solar System • Meteorites! Solar System 2/8/07

  22. Today’s quiz • Be sure to fill in the ovals for your name (last name first!!!) • Closed book, closed notes, no electronic devices • The quiz has 15 questions (front and back) • Fill in the oval corresponding to your answer on the scantron sheet using a #2 pencil • Only turn in the scantron sheet – you may take the quiz itself with you when you leave • You may leave when you are finished – but please do so as quietly as possible and leave through the North Entrance (upper right door) Solar System 2/8/07

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