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The Solar System

The Solar System. 09.19.07 / 09.20.07. Essential Questions. What are distinguishing features of solar system bodies? What are Kepler’s laws and how do they apply to planetary motion? What is the nebular hypothesis?. Overview of the solar system. Solar system includes Sun

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The Solar System

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  1. The Solar System 09.19.07 / 09.20.07

  2. Essential Questions • What are distinguishing features of solar system bodies? • What are Kepler’s laws and how do they apply to planetary motion? • What is the nebular hypothesis?

  3. Overview of the solar system • Solar system includes • Sun • Eight planets and their satellites • Asteroids • Comets • Meteoroids

  4. Kuiper Belt • 2.8 - 4.6 billion miles away • Probably tens-of-thousands of rocky, icy objects • Includes Pluto • Discovered circa 1992 • Predicted in 1951 by Gerald Kuiper

  5. The solar system

  6. The orbits of most asteroids lie between Mars and Jupiter

  7. Minor members of the solar system • Asteroids • Most lie between Mars and Jupiter • Small bodies – largest (Ceres) is about 620 miles in diameter • Some have very eccentric orbits • Irregular shapes • Origin is uncertain

  8. Image of asteroid 951 (Gaspra)

  9. Minor members of the solar system • Comets • Often compared to large, "dirty snowballs" • Composition • Frozen gases • Rocky and metallic materials

  10. Minor members of the solar system • Comets • Origin • Not well known • Form at great distance from the Sun

  11. Comet Hale-Bopp

  12. Minor members of the solar system • Meteoroids • Calledmeteorswhen they enter Earth's atmosphere • A meteor shower occurs when Earth encounters a swarm of meteoroids associated with a comet's path • Meteoroids are referred to as meteorites when they are found on Earth

  13. Overview of the solar system • A planet's orbit lies in an orbital plane • Similar to a flat sheet of paper • The orbital planes of the planets are inclined • Planes of seven planets lie within 3 degrees of the Sun's equator • Mercury's is inclined 7 degrees • Pluto's is inclined 17 degrees (That crazy Pluto)

  14. Overview of the solar system • Two groups of planets occur in the solar system • Terrestrial (Earth-like) planets • Mercury through Mars • Small, dense, rocky • Low escape velocities

  15. Overview of the solar system • Two groups of planets occur in the solar system • Jovian (Jupiter-like) planets • Jupiter through Neptune • Large, low density, gaseous • Massive • Thick atmospheres composed of hydrogen, helium, methane, and ammonia • High escape velocities • Pluto not included in either group (oddball)

  16. The planets drawn to scale

  17. Evolution of the planets • Nebular hypothesis • Planets formed about 5 billion years ago • Solar system condensed from a gaseous nebula • As the planets formed, the materials that compose them separated • Dense metallic elements (iron and nickel) sank toward their centers • Lighter elements (silicate minerals, oxygen, hydrogen) migrated toward their surfaces

  18. Kepler’s Laws • Law 1: The planet orbit is ellipses with the Sun at one of two foci • Law 2: The line connecting the planet to the Sun sweeps equal areas in equal time • Law 3: The periods of planets’ revolutions is proportional to their distances from the Sun

  19. Law 1 http://astro.isi.edu/notes/gravity.html

  20. Law 2 http://burro.astr.cwru.edu/Academics/Astr221/Gravity/kepler2.htm

  21. Law 3 http://hyperphysics.phy-astr.gsu.edu/hbase/kepler.html

  22. Eight or Nine? • Pluto • Discovered in 1930 • Highly eccentric orbit causes it to occasionally travel inside the orbit of Neptune, where it resided from 1979 through February 1999 • Moon (Charon) discovered in 1978

  23. Pluto and its moon Charon as compared to the size of Earth

  24. A decision to make • With the discovery of the Kuiper Belt, astronomers need to make on of two choices: • allow the possibility of many, many more planets • create a more restrictive definition of planet • They chose this second option • They then created possible definitions

  25. Potential definition 1 • A planet would need to a) revolve around a star, b) be massive enough to have formed into a round shape, c) not be a moon, and d) not be another star • This option would have resulted in 12 planets, with more possible in the future

  26. Potential definition 2 • The same as the first with one addition • the planet must have “cleared the neighborhood around its orbit.” • Because Pluto’s orbit crosses paths with Neptune, it would not qualify • This definition results in 8 planets • This is the one the International Astronomical Union chose to accept • Pluto hasn’t changed, just our definition of planet

  27. Light pollution http://epod.usra.edu/archive/epodviewer.php3?oid=92448

  28. Source: University of Hawaii

  29. Houses cause pollution too

  30. Better lighting

  31. Source: NASAsee also p. 664 in home text

  32. Resources • International Dark-Sky Society • International Astronomical Union • Light Pollution Abatement Program (LPAP) Canada

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