ASTR 200 : Lecture 6 Introduction to the Solar System Pearson Education Inc., publishing as Addison-Wesley

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1 ASTR 200 : Lecture 6 Introduction to the Solar System Pearson Education Inc., publishing as Addison-Wesley

2 Comparative Planetology Studying the similarities among and differences between the planets this includes moons, asteroids, & comets This approach is useful for learning about: the physical processes which shape the planets the origin and history of our Solar System the nature of planetary systems around other stars Pearson Education Inc., publishing as Addison-Wesley

3 Basic patterns that need explanation All planets orbit Sun in same sense (counterclockwise viewed from N) All planets orbit in almost same plane, with e~0 Sun contains 99.9% of Solar System's mass Inner planets are rocky, while outer the planets/satellites are icy or gas-rich Crater production (especially impact basins) larger in past Pearson Education Inc., publishing as Addison-Wesley

4 An obvious solar system division Planets fall into two main categories A) Terrestrial (i.e. Earth-like) B) Jovian (i.e. Jupiter-like or gaseous) 4 Danger: Inner and Outer are often used, but they only work until Neptune 2004 Pearson Education Inc., publishing as Addison-Wesley

5 5 Mars Terrestrial 2004 Pearson Education Inc., publishing as Addison-Wesley Neptune Jovian

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9 The Layout of the Solar System Large bodies in the Solar System have orderly motions - planets orbit counterclockwise in same plane - orbits are almost circular - the Sun and most planets rotate counterclockwise (seen from N) - most moons orbit their planet counterclockwise Pearson Education Inc., publishing as Addison-Wesley

10 A Few Exceptions to the Rules Both Uranus & Pluto are tilted on their sides. Venus rotates backwards (i.e. clockwise). Triton orbits Neptune backwards. Earth is the only terrestrial planet with a relatively large moon. Is Pluto (and other large trans-neptunian objects) to be considered a planet? Pearson Education Inc., publishing as Addison-Wesley

11 The Sun King of the Solar System How does the Sun influence the planets? Its gravity regulates the orbits of the planets. Its heat is the primary factor which determines the temperature of the planets. It provides practically all of the visible light in the Solar System. High-energy particles streaming out from the Sun influence planetary atmospheres and magnetic fields Pearson Education Inc., publishing as Addison-Wesley

12 Mercury : Battered Remnant Recently explored by the Messenger spacecraft Impact scarred like our Moon Pearson Education Inc., publishing as Addison-Wesley

13 Venus: An extreme climate Earth's twin in size Massive choking atmosphere Clue to planetary climates Pearson Education Inc., publishing as Addison-Wesley

14 Earth: The cradle of life A complex biosphere A massive Moon Geologic complexity Pearson Education Inc., publishing as Addison-Wesley

15 Mars : The most likely second home? Earth-like in some ways Perhaps had oceans? Surface has great variety Pearson Education Inc., publishing as Addison-Wesley

16 Jupiter : Lord of the heavens More mass than all other planets put together First of the jovian planets Moons the size of planets Pearson Education Inc., publishing as Addison-Wesley

17 Ringed Saturn Rings are incredibly flat Interesting contrasts to Jupiter Pearson Education Inc., publishing as Addison-Wesley

18 Uranus and Neptune : the ice giants Much smaller than Jupiter and Saturn Dominantly ices, not gases Pearson Education Inc., publishing as Addison-Wesley

19 The Solar System has two 'small body belts' Pearson Education Inc., publishing as Addison-Wesley

20 The main asteroid belt Swarms of asteroids and comets populate the Solar System Rocky asteroids, mostly between Mars and Jupiter Pearson Education Inc., publishing as Addison-Wesley

21 Neptune's orbit Comets Pluto's orbit - Visible comets (those with tails) when they make it to the inner Solar System (rare) Reservoirs are the : - Kuiper Belt - Oort cloud Oort cloud Main asteroid belt Pearson Education Inc., publishing as Addison-Wesley

22 Comets and Asteroids Small bodies that hold big clues to the birth of planets The two classes are mainly composition Rocky asteroids Icy comets This is linked to where they formed Pearson Education Inc., publishing as Addison-Wesley

23 'Orbital elements' are the parameters that describe the shape and orientation of the orbit - In this course we are not worrying about the orientation, so the only orbital elements we discussed were a and e Pearson Education Inc., publishing as Addison-Wesley