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Formation of Our Solar System

Formation of Our Solar System. Image: Lunar and Planetary Laboratory: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=178. 1. Some data to explain: 1. Planets isolated 2. Orbits ~circular / in ~same plane

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Formation of Our Solar System

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  1. Formation of Our Solar System Image: Lunar and Planetary Laboratory: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=178 1

  2. Some data to explain: 1. Planets isolated 2. Orbits ~circular / in ~same plane 3. Planets (and moons) travel along orbits in same direction…. same direction as Sun rotates (CCW) Venus slowly rotates CW Uranus on its side Pluto on its side – captured asteroid? Moons go CCW around planets (few exceptions) Lunar and Planetary Institute image at http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=175 2

  3. Solar System is highly differentiated • Terrestrial planets • Slow rotators, few or no moons • Gas Giants • Fast rotators, many moons • Asteroids • Old • Different from rocky or gaseous planets • Comets • Old, icy • Do not move on same plane as planets 3

  4. Planets, most moons, and asteroids revolve around the Sun in the same direction (CCW) • They all move in ~ circular orbits • Pluto-special case • Orbit is highly inclined (18°) • oval shape 4

  5. Some more data to explain: 4. Most planets rotate in this same direction Mercury 0° Venus 177° Earth 23° Mars 25° Jupiter 3° Saturn 27° Uranus 98° Neptune 30° 5 NASA images edited by LPI

  6. And some more data to explain: 5. Solar System highly differentiated: Terrestrial Planets (rocky, dense with density ~4-5 g/cm3) Jovian Planets (light, gassy, H, He, density 0.7-2) Images: Lunar and Planetary Laboratory: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=178 6

  7. How Did We Get a Solar System? Image: LPI Active region of Star formation in the Large Magellanic Cloud (LMC) – satellite galaxy of Milky Way (Hubble) Huge cloud of cold, thinly dispersed interstellar gas and dust (mostly H & He) Hubble image at http://hubblesite.org/newscenter/archive/releases/nebula/emission/2006/41/image/a/ 7

  8. How Did We Get a Solar System? Image: LPI Concentrations of dust and gas in the cloud; material starts to collect (gravity > magnetic forces) Hubble image at http://hubblesite.org/newscenter/archive/releases/nebula/emission/2005/35/image/a/ 8

  9. How Did We Get a Solar System? Gravity concentrates most stuff near center Heat and pressure increase Collapses – central proto-sun rotates faster (probably got initial rotation from the cloud) 9 Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_1.html

  10. How Did We Get a Solar System? • Rotating, flattening, contracting disk - solar nebula! • Equatorial Plane • Orbit Direction 10 NASA artwork at http://en.wikipedia.org/wiki/Image:Ra4-protoplanetary-disk.jpg

  11. How Did We Get a Solar System? • After ~10 million years, material in center of nebula hot enough to fuse Hydrogen (H) • “...here comes the Sun…” NASA/JPL-Caltech Image at http://www.nasa.gov/vision/universe/starsgalaxies/spitzer-20060724.html 11

  12. How Did We Get a Solar System? • Metallic elements (Mg, Si, Fe) condense into solids at high temps. Combined with Oxygen to make tiny grains • Lower temp (H, He, CH4, H2O, N2, ice) - outer edges • Planetary Compositions Hubble photo at http://hubblesite.org/newscenter/archive/releases/star/protoplanetary-disk/2005/10/image/a/layout/thumb/ 12

  13. How Did We Get a Solar System? • Inner Planets: • Hot – Silicate minerals, metals, no light elements, ice • Begin to stick together with dust  clumps 13 Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_3.html

  14. How Did We Get a Solar System? • Outer Solar System • Cold – ices, gases – 10x more particles than inner • May have formed icy center, then captured lighter gases (Jupiter and Saturn first? Took H and He?) • Leave C,O, and N for the others 14 Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_5.html

  15. Terrestrial planets • Heavier elements stable at higher temperature • Condensed in inner nebula • Gas giants • Lighter elements (H, He, C, O, N) stable at lower temperature • Condensed in outer nebula 15

  16. Where do Comets Originate? 16

  17. Orbital paths of comets • Highly elliptical (oval-shaped) • 1 complete orbit is called a period • Short-period comets • Revolve around the Sun less than 200 yrs • E.g. Comet Halley • Paths are close to the same plane of orbit as planets • Orbit is the same direction as the Sun • Originate from the Kuiper belt 17

  18. Long-period comets • Longer than 200 years to go around once • Orbital path is random • Direction and plane of orbit • E.g. Comet Hale-Bopp • Originated in Oort cloud • Spherical cloud, 20 trillion miles beyond the Sun 18

  19. How Did We Get a Solar System? • Accretion - particles collide and stick together … or break apart … gravity not involved if small pieces • Form planetesimals, up to a few km across 19 Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_3.html

  20. How Did We Get a Solar System? • Gravitational accretion: planetesimals attract stuff • Large protoplanets dominate, grow rapidly, clean up area ( takes ~10 to 25 My) 20 Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_4.html

  21. Smaller protoplanets (inner solar nebula) • Unable to accrete gas because of their higher temperature • Obtain their atmospheres from the impact of comets • Largest protoplanets (outer solar nebula) • Accrete gas because of their cooler temperature • Strongly influence the orbits of the remaining comets • Either send them out to the Oort cloud or • Send them inward where they collide with the terrestrial planets 22

  22. How Did We Get a Solar System? The Asteroid Belt ? Should have been a planet instead of a debris belt? Jupiter kept it from forming Eros image at http://solarsystem.nasa.gov/multimedia/gallery.cfm?Category=Planets&Object=Asteroids&Page=1 23

  23. How Did We Get a Solar System? Beyond the Gas Giants - Pluto, Charon and the Kuiper Belt objects Chunks of ice and rock material Little time / debris available to make a planet – slower!! Taken from Hubble Telescope Charon is Pluto’s moon, only a Little smaller than Pluto Pluto’s surface temp. is as low as -400° F From the surface of Pluto, the Sun looks like a very bright star 24

  24. Early in the Life of Planets • Planetesimals swept up debris • Accretion + Impacts = HEAT • Eventually begin to melt materials • Iron, silica melt at different temperatures • Iron sank – density layering 25 Image from LPI: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=168

  25. Mercury • Average density of 5430 kg/m3 • Second highest density of all planets • Like Earth, has an Iron core • 2/3 to ¾ of the radius of the planet! • Iron-Nickel core 26

  26. Venus • Composition ~ to Earth • Crust 10-30 km thick • Mantle • Core – Iron-Nickel • Average density is 5240 kg/m3 27

  27. Earth • Crust, mantle, and core • Crust • ~ 30 km thick for land (granite) • ~ 5 km for oceanic crust (basalt) • Mantle • Core, Iron-Nickel • Liquid outer core • Inner solid core • Average density ~ 5520 kg/m3 28

  28. Mars • ~ ½ the diameter of Earth • Crust • Mantle • Core , • Iron-Nickel • and Iron sulfide • Density ~ 3930 kg/m3 29

  29. Pluto • Structure not very well understood • Surface is covered with methane ice • Surface temp ~ 400° F • Frozen methane shows a bright coloration • Density ~ 2060 kg/m3 • This low of a density suggests that the planet must be a mix of rock and ice 30

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