2How was it formed The Nebular Theory Started as nebula about 5 billion years agoComposed of hydrogen and heliumNearby supernova sent shock waves through galaxycaused gases to be pulled inwardsupplied new elementsShrank to a spinning disk –10 billion kilometers acrossGravity heated center to protostar - the sun
3How was it formed Other matter spun around the new sun gathered into clumps- protoplanetsNear the sun the light weight gases boiled awayMercury, Venus, Earth, MarsIn those far away the gases did not boil awayJupiter, Saturn, Uranus, Neptunethe gas giants
4How was it formedAround the protoplanets smaller clumps formed moons or satellites.Pluto is thought to be a moon of Neptune that broke away.Asteroid belt- clumps of rocks between Mars and JupiterJupiter’s gravity stopped a planet from formingOort Cloud- Near the edge clumps of matter- home of comets.
5History People have used the stars for ages. Used constellations to set planting timesUsed constellations to guide travelsSome lights in the sky wandered through the constellationsCalled them “planets” which is Greek for wanderers
6Ptolemy Greek scientist Placed earth at center of universe Other objects moved in orbits around the earthBecause circle was considered a perfect shape, thought they moved in circular paths
7Copernicus Polish astronomer Found Earth and planets revolved around sunIn the same directionAt different speedsThought the orbits were circular
8Kepler German mathematician and astronomer Used others observations (Tycho Brahe)Calculated the orbits of planets were ovals or ellipsesCloser to the sun - shortest time of orbitFarther from the sun - greater time
25Saturn Similar to Jupiter Clouds, magnetosphere, gives off heat Rotates in 10 hours - makes it bulge in the middle and flat at the polesLow density- would float in water
26SaturnMany ringscomplex systemmade of waterweave in and out
27SaturnMany moons -Titan- the largest is like the early Earth.
28Uranus Twice as far from the sun as Saturn. Covered with ocean of superheated waterTilted on axisRings of methane iceMany moons
29Neptune Like Uranus Hydrogen and helium atmosphere Surface of water and methaneRings made of dustEight moons
30Triton Large moon Thought to be captured Retrograde revolution out of plane of Neptune’s rotation
31Pluto Moon sized Made of methane Pink atmosphere on the sunny side Moon Charon 1/2 the size of PlutoScientists think it is a moon broken away from NeptuneOrbit crosses NeptuneOrbit not in plane with other planets
32Other Stuff Meteor- the shooting star -the light you see the sky Meteoroid- solid rocky objects circling the sunMeteorite- When a meteor hits the groundMost don’t because they burn up in the atmosphereSome meteoroids are iron and nickelSome are stonyOthers are combinations
33Meteorites Leave a crater where they hit the ground Meteorite Crater in ArizonaEvidence of meteorites from the moon and from Mars
34Comets Chunks of dust and gas from the Oort Cloud that orbit the sun When it gets close to the sun it gets hotterSome of the gas and dust form a cloud around the head called the comaSolar wind pushes the gases away from the sun and make the tailTail is pushed by the solar windTail always points way from the sun
37Comets Comets orbit the sun Long period comets take a long time to go aroundThousands of yearsShort period comets return every few yearsHalley’s every 75 to 79 yearsLast time in 1986Suspect a nearby star disrupts the Oort cloud to send more comets toward sun.
38Asteroids Chunks of planetlike material floating in space Most between Mars and JupiterMost 1km in diameterCeres- 1000km in diameterSome pass near EarthCaused craters on moon, and inner planets
39Looking for life On other planets Need liquid water and moderate temperatures.Earth is just the right distance to have the right temperaturesLooking for evidence of former life on Mars- used to have water.On Titan atmosphere like early earth.
40Rockets Rely on Netwon’s Third law of Motion For every action there is an equal and opposite reaction.Reward blast of hot gases causes rocket to shoot forward.First developed by Chinese in 1000Tube full of gunpowder with cap on one end.
41Escape VelocityThe minimum speed needed to leave the gravitational pull.Depends on mass of planet and distance from the center of planet.Earth 11.2 km/secMoon 2.3 km/secJupiter 63.4 km/secPluto 0.3 km/secSun 616 km/sec
42Rockets and Escape Velocity Solid rockets burn up fuel quicklyLarge thrust earlyGravity eventually slows them down.Liquid fuels provide continuous thrust.Goddard- gasoline and liquid oxygenSpace shuttle liquid hydrogen and liquid oxygenMultiple stages to reduce weight.
43Spacecraft Probes have gone past all the planets except Pluto Have sampled comets tailsHave taken pictures of planets and moons.