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Solar System Overview

Solar System Overview. Earth, as viewed by the Voyager spacecraft. What does the solar system look like?. There are eight major planets with nearly circular orbits. Pluto and Eris are smaller than the major planets and have more elliptical orbits.

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Solar System Overview

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  1. Solar System Overview Earth, as viewed by the Voyager spacecraft

  2. What does the solar system look like?

  3. There are eight major planets with nearly circular orbits. • Pluto and Eris are smaller than the major planets and have more elliptical orbits.

  4. Planets all orbit in same direction and nearly in same plane.

  5. What are the major features of the Sun and planets? Sun and planets to scale

  6. Sun • Over 99.9% of solar system’s mass • Made mostly of H/He gas (plasma) • Converts 4 million tons of mass into energy each second

  7. Mercury • Made of metal and rock; large iron core • Desolate, cratered; long, tall, steep cliffs • Very hot and very cold: 425C (day)–170C (night)

  8. Venus • Nearly identical in size to Earth; surface hidden by clouds • Hellish conditions due to an extreme greenhouse effect • Even hotter than Mercury: 470C, day and night

  9. Earth Earth and Moon with sizes shown to scale • An oasis of life • The only surface liquid water in the solar system • A surprisingly large moon

  10. Mars • Looks almost Earth-like, but don’t go without a spacesuit! • Giant volcanoes, a huge canyon, polar caps, more • Water flowed in distant past; could there have been life?

  11. Jupiter • Much farther from Sun than inner planets • Mostly H/He; no solid surface • 300 times more massive than Earth • Many moons, rings

  12. Jupiter’s moons can be as interesting as planets themselves, especially Jupiter’s four Galilean moons. • Io (shown here): active volcanoes all over • Europa: possible subsurface ocean • Ganymede: largest moon in solar system • Callisto: a large, cratered “ice ball”

  13. Saturn • Giant and gaseous like Jupiter • Spectacular rings • Many moons, including cloudy Titan

  14. Rings are NOT solid; they are made of countless small chunks of ice and rock, each orbiting like a tiny moon. Artist’s conception

  15. Cassini probe arrived July 2004 (launched in 1997).

  16. Uranus • Smaller than Jupiter/Saturn; much larger than Earth • Made of H/He gas and hydrogen compounds (H2O, NH3, CH4) • Extreme axis tilt • Moons and rings

  17. Neptune • Similar to Uranus (except for axis tilt) • Many moons (including Triton)

  18. Pluto (and Other Dwarf Planets) • Much smaller than major planets • Icy, comet-like composition • Pluto’s main moon (Charon) is of similar size

  19. Motion of Large Bodies • All large bodies in the solar system orbit in the same direction and in nearly the same plane. • Most also rotate in that direction.

  20. Two Major Planet Types • Terrestrial planets are rocky, relatively small, and close to the Sun. • Jovian planets are gaseous, larger, and farther from the Sun.

  21. Swarms of Smaller Bodies • Many rocky asteroids and icy comets populate the solar system.

  22. Notable Exceptions • Several exceptions to the normal patterns need to be explained.

  23. Formation of the Solar System

  24. What properties of our solar system must a formation theory explain? • Patterns of motion of the large bodies • Orbit in same direction and plane • Existence of two types of planets • Terrestrial and jovian • Existence of smaller bodies • Asteroids and comets • Notable exceptions to usual patterns • Rotation of Uranus, Earth’s Moon, etc.

  25. What theory best explains the features of our solar system? • The nebular theory states that our solar system formed from the gravitational collapse of a giant interstellar gas cloud—the solar nebula. (Nebula is the Latin word for cloud.) • Kant and Laplace proposed the nebular hypothesis over two centuries ago. • A large amount of evidence now supports this idea.

  26. Where did the solar system come from?

  27. Conservation of Angular Momentum • Rotation speed of the cloud from which our solar system formed must have increased as the cloud contracted.

  28. Flattening • Collisions between particles in the cloud caused it to flatten into a disk.

  29. Disks around Other Stars • Observations of disks around other stars support the nebular hypothesis.

  30. Why are there two major types of planets?

  31. Inside the frost line: too hot for hydrogen compounds to form ices Outside the frost line: cold enough for ices to form

  32. How did the terrestrial planets form? • Small particles of rock and metal were present inside the frost line. • Planetesimals of rock and metal built up as these particles collided. • Gravity eventually assembled these planetesimals into terrestrial planets.

  33. Accretion of Planetesimals • Many smaller objects collected into just a few large ones.

  34. How did the jovian planets form? • Ice could also form small particles outside the frost line. • Larger planetesimals and planets were able to form. • Gravity of these larger planets was able to draw in surrounding H and He gases.

  35. Moons of jovian planets form in miniature disks.

  36. Where did asteroids and comets come from?

  37. Asteroids and Comets • Leftovers from the accretion process • Rocky asteroids inside frost line • Icy comets outside frost line

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