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The Solar System

The Solar System. Chapter 15. Planets, moons and other bodies. Solar System Sun ~ 10 planets ? ~100 moons Thousands of asteroids, millions of icy bodies, comets, … Astronomical unit (AU) Average Earth-Sun distance 1.5x10 8 km (93 million miles)

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The Solar System

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  1. The Solar System Chapter 15

  2. Planets, moons and other bodies Solar System Sun ~ 10 planets ? ~100 moons Thousands of asteroids, millions of icy bodies, comets, … Astronomical unit (AU) Average Earth-Sun distance 1.5x108 km (93 million miles) Planet classification: size, density and atmosphere Terrestrial planets Mercury, Venus, Earth and Mars Mostly rocky materials, metallic nickel and iron Giant planets Jupiter, Saturn, Uranus and Neptune Mostly hydrogen, helium and methane Pluto and Quaoar (Kwah-o-ar) In a class by themselves True planet?

  3. Quaoar Orbits sun 288 years. Size 1250 km (1/2 size of Pluto) Dis. By Mike Brown and Chad Trujilo California Institute of Technology Named after god of Tongva Indian- original tribe located on campus of Cal. Tech. in Los Angeles. Is it a real Planet? Scientist believe that it and Pluto are members of the “Kuiper-belt” a second asteroid belt at the fringes of our solar system. Called “ Ice dwarfs” If Pluto was discovered today would not be classified as planet. The discovery of Quaoar puts more doubt on Pluto being classified as a planet.

  4. The order of the planets

  5. Mercury Innermost planet Highly elliptical orbit Average distance ~ 0.4 AU Has the shortest revolution of all planets with ~ 3 months Rotational period ~ 59 days Visible shortly after sunset or before sunrise Highly cratered; no atmosphere

  6. Venus Orbital distance ~ 0.7 AU Morning and evening “star” Exhibits phases, like the Moon Rotational motion opposite orbital motion Venusian “day” longer than Venusian “year” Visited by numerous probes Mostly CO2 atmosphere, high temperature and pressure Surface mostly flat but varied

  7. Mars Orbital distance ~ 1.5 AU Geologically active regions Inactive volcanoes Canyons Terraced plateaus near poles Flat regions pitted with craters Thin atmosphere, mostly CO2 Strong evidence for liquid water in past Numerous space probes Two satellites- Phobos and Demos

  8. Jupiter ~ 5 AU from Sun Most massive planet 318 times Earth’s mass Mostly H and He with iron-silicate core Dynamic atmosphere H2, He, ammonia, methane, water, … Great Red Spot 39 widely varying satellites

  9. Jupiter's Largest Moons Four largest satellites were discovered by Galileo using his small telescope, Io, Callisto, Europa, and Ganymede.

  10. Saturn 9.5 AU from Sun Rings of particles Density = 0.7 that of water Surface similar to Jupiter’s 30 satellites Titan: only moon with substantial atmosphere

  11. Uranus, Neptune and Pluto Uranus (~19 AU) and Neptune: (~30 AU) Outermost giant planets Similar internal structures Pluto: Smaller than the Moon 70% rock; 30% water ice; tenuous, thin atmosphere Unusual orbit Tilted 17o from ecliptic Crosses Neptune’s

  12. Planet summary

  13. Smaller bodies of the Solar System Comets, asteroids, meteorites Leftover from solar and planetary formation Mass of smaller bodies may be 2/3 of total Solar System mass Bombard larger objects Comet Shoemaker-Levy 9 fragments (bottom)… … and strikes Jupiter (July 1994)

  14. Comet origins Oort cloud Origin of long-period comets (>200 years) 30 AU to light-year away Kuiper belt Origin of short-period comets (<200 years) Disk-shaped region 30-100 AU from Sun Gravitational nudges deflect objects toward Sun

  15. Comet structure Small, solid objects “Dirty snowball” model Frozen water, CO2, ammonia, and methane Dusty and rocky bits Comet head Solid nucleus and coma of gas Two types of tails Ionized gases Dust Tail points away from Sun

  16. Asteroids Located in belt between Mars and Jupiter Sizes: up to 1,000 km Varied composition Inner belt: stony Outer belt: dark with carbon Others: iron and nickel Formed from original solar nebula Prevented from clumping by Jupiter nearby

  17. Meteors and meteorites Meteoroids Remnants of comets and asteroids Meteor Meteoroid encountering Earth’s atmosphere Meteor showers: Earth passing through comet’s tail Meteorite Meteoroid surviving to strike Earth’s surface Iron, stony or stony-iron

  18. Origin of the Solar System Protoplanet nebular model Stage A Formation of heavy elements in many earlier stars and supernovas Concentration in one region of space as dust, gas and chemical compounds

  19. Origin of the Solar System Stage B Formation of large, rotating nebula Gravitational contraction, spin rate increases Most mass concentrates in central protostar Remaining material forms outer disk Material in outer disk begins clumping

  20. Origin of the Solar System Stage C Protosun becomes a star Solar ignition flare-up may have blown away hydrogen and helium atmospheres of inner planets Protoplanets heated, separating heavy and light minerals Larger bodies cooled slower, with heavy materials settling over longer times into central cores

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