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17-1: What is the Solar System The Sun contains 99.85% of all the matter in the Solar System. The planets revolve around the Sun in orbits Most planets orbit the sun in a counter-clockwise fashion Nebula spinning cloud of gas and dust in space One theory to explain how the solar system formed is a nebula http://www.picturethecosmos.co m/ Inner Planets: Small Rocky Worlds Planets – are small, dense, rocky worlds with less atmosphere than the other type of planet. Terrestrial They have craters, no rings, very few moons, very small. ○ Mercury ○ Venus ○ Earth ○ Mars Outer Planets: Gas Giants Planets – are large, gaseous, low density worlds. Thick gaseous mostly hydrogen atmospheres, rings, lots of moons, and very large in comparison to terrestrial planets. Jovian Jupiter Saturn Neptune Uranus Pluto – doesn’t fit either category. Pluto is a small icy world clearly different from either the Jovian and Terrestrial worlds. Pluto Sun’s Family Sun’s family consists of 8 planets, > 162 moons, & at least 3 dwarf planets 17-2 Orbits Gravity force of attraction btw 2 objects with mass Gravity keeps the planets in orbits flying around the Sun All planets travel in elliptical orbits Planets travel fastest at perihelion (closest to Sun) & slower at aphelion (farthest from Sun 17-3 Our Moon American landed on the Moon on July 20,1969 The Moon’s gravity is 1/6 that of Earth The Moon has no liquid water Temp. ranges from 100°C to below -200°C (100°C is boiling) 17-3 Features of Our Moon Maria smooth, dark areas on the Moon that are broad, flat plains; maria means “seas” Light areas that are mountains or highlands; some are higher than on Earth Craters caused by large objects striking the surface or erupting volcanoes 17-4 Other Moons Satellite an object that orbits another body in space Moons are natural satellites All planets except Mercury & Venus have 1 or more moons Moons of the Inner Planets Mercury has 0 moons Venus has 0 moons Earth has 1 moon Mars has 2 moons; Deimos & Phobos Moons of the Outer Planets Jupiter has at least 63 moons; Ganymede,Callisto, Io, & Europa are the 4 largest Saturn has 59 moons; Titan is the largest Uranus has 27 moons; Titania & Oberon are the largest Neptune has 13 moons; Triton & Nereid are visible 17-5 Mercury Mercury closest planet to the Sun ○Dry ○Rocky ○No atmosphere ○Temp. ranges from 430°C to 170°C ○Covered with craters 17-5 Venus Venus similar to Earth in size, mass, & density Very hostile environment Highest temp. of all planets 90 times more air pressure than Earth Carbon dioxide atmosphere & clouds of sulfuric acid cause a runaway Greenhouse Effect Retrograde rotation (east to west) Has smooth plains, mountains, valleys 17-5 Earth Third planet from Sun Only planet with oceans of liquid water Only planet with life because it has moderate temp., liquid water, & atmosphere w/ O2 17-6 Mars Fourth planet from Sun Orbit period687 days; rotation24 hr. 37 min. ½ diameter of Earth Has volcanoes, polar icecaps, craters, river channels Thin CO2 atmosphere No visible water 17-6 Mars cont. Cold, dry world; colder than Antarctica in winter, as warm as the Midwest in spring Winds up to 100 km/h cause dust storms Volcanoes bigger than Earth Mars has less gravity Canyon bigger than U.S. 17-7 Asteroids & Meteoroids Asteroid belt btw. Mars & Jupiter Asteroids leftover debris from the formation of solar system that orbit the Sun Pieces of rock and metal 17-7 cont. Meteoroids small chunks of asteroids that travel in space Meteor rock or metal that enters a planet’s atmosphere Meteorite rock that hits a planet’s surface 17-8 Jupiter Largest planet 5th planet from Sun and 1st gas giant Made up mostly of Hydrogen and Helium Has faint rings of ice and dust Best known feature is Great Red Spot raging hurricane 17-8 Saturn 2nd largest planet 6th planet from Sun & 2nd gas giant Made mostly of Hydrogen & Helium Least dense of all planets; would float in water Best known for its rings 17-9 Uranus 3rd largest planet 7th planet from Sun & 3rd gas giant Made mostly of Hydrogen and Helium Atmosphere contains methane Appears to lie on its side Has faint rings 17-9 Neptune 4th largest planet 8th from Sun & last gas giant Made mostly of Hydrogen & Helium Upper atmosphere is methane Has Great Dark Spot similar to Jupiter’s Great Red Spot Winds blow east to west @1500 km/h 17-9 Dwarf Planets In 2006 Pluto was reclassified as a dwarf planet Dwarf planet small, planetlike object that orbit the Sun, but share their orbits with other objects Pluto, Ceres, Eris 17-9 Kuiper Belt Kuiper belt is btw Neptune & outer regions of solar system 100 million fragments of ice & rock Includes dwarf planets & their moons 17-10 Comets Comet lump of ice, frozen gas, & dust Orbit the Sun in long, ellipses that go beyond Pluto Has 3 parts: Nucleus dirty ice ball Coma cloud of gas surrounds Tail(s) melting particles that point away from the Sun 17-10 Comets cont. Comets come from the Oort Cloud Far beyond Neptune’s orbit May contain trillions of inactive comets