Chapter 3 The Solar System

How was it formed The Nebular Theory Started as nebula about 5 billion years ago Composed of hydrogen and helium Nearby supernova sent shock waves through galaxy caused gases to be pulled inward supplied new elements Shrank to a spinning disk –10 billion kilometers across Gravity heated center to protostar - the sun

How was it formed Other matter spun around the new sun gathered into clumps- protoplanets Near the sun the light weight gases boiled away Mercury, Venus, Earth, Mars In those far away the gases did not boil away Jupiter, Saturn, Uranus, Neptune the gas giants

How was it formed Around 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 Jupiter Jupiter’s gravity stopped a planet from forming Oort Cloud- Near the edge clumps of matter- home of comets.

History People have used the stars for ages. Used constellations to set planting times Used constellations to guide travels Some lights in the sky wandered through the constellations Called them “planets” which is Greek for wanderers

Ptolemy Greek scientist Placed earth at center of universe Other objects moved in orbits around the earth Because circle was considered a perfect shape, thought they moved in circular paths

Copernicus Polish astronomer Found Earth and planets revolved around sun In the same direction At different speeds Thought the orbits were circular

Kepler German mathematician and astronomer Used others observations (Tycho Brahe) Calculated the orbits of planets were ovals or ellipses Closer to the sun - shortest time of orbit Farther from the sun - greater time

Planets Move in an elliptical orbit

Planets Period of revolution the time it takes to go once around the sun one year Mercury 88 days, Pluto 248 years

What keeps them there? Law of inertia - objects motion won’t change unless acted upon by an outside force. Won’t change speed or direction Why do they curve? Gravity pulls them toward the sun

What keeps them there? Inertia Gravity

Rotation Planets spin on their axes One rotation is a day Mercury 58 days, Jupiter 10 hours

Special Features of the Planets Mercury Many Craters no atmosphere no erosion Slow rotation makes it hot and cold

Venus Thick atmosphere of carbon dioxide Sulfuric acid clouds Greenhouse effect carbon dioxide traps heat. Makes Venus hotter than Mercury Retrograde rotation - rotates backward

Mars Red planet- covered by iron oxide (rust) Mons Olympus - Largest volcano in the solar system Two ice caps north - water -never melts south -carbon dioxide melts in summer

Two moons of Mars Phobos Deimos

Jupiter

Jupiter Largest of the gas giants Huge storms - red spot Small solid core Liquid metal layer makes a huge magnetic field Magnetosphere Gives off more heat than it receives from the sun Thin ring

Jupiter Gives off more heat than it receives from the sun. By far the largest planet.

16 moons 4 seen by Galileo helped change science

Saturn Similar to Jupiter Clouds, magnetosphere, gives off heat Rotates in 10 hours - makes it bulge in the middle and flat at the poles Low density- would float in water

Saturn Many rings complex system made of water weave in and out

Saturn Many moons - Titan- the largest is like the early Earth.

Uranus Twice as far from the sun as Saturn. Covered with ocean of superheated water Tilted on axis Rings of methane ice Many moons

Neptune Like Uranus Hydrogen and helium atmosphere Surface of water and methane Rings made of dust Eight moons

Triton Large moon Thought to be captured Retrograde revolution out of plane of Neptune’s rotation

Pluto Moon sized Made of methane Pink atmosphere on the sunny side Moon Charon 1/2 the size of Pluto Scientists think it is a moon broken away from Neptune Orbit crosses Neptune Orbit not in plane with other planets

Other Stuff Meteor- the shooting star -the light you see the sky Meteoroid- solid rocky objects circling the sun Meteorite- When a meteor hits the ground Most don’t because they burn up in the atmosphere Some meteoroids are iron and nickel Some are stony Others are combinations

Meteorites Leave a crater where they hit the ground Meteorite Crater in Arizona Evidence of meteorites from the moon and from Mars

Comets Chunks of dust and gas from the Oort Cloud that orbit the sun When it gets close to the sun it gets hotter Some of the gas and dust form a cloud around the head called the coma Solar wind pushes the gases away from the sun and make the tail Tail is pushed by the solar wind Tail always points way from the sun

Solar wind Coma Tail Nucleus

Comets Comets orbit the sun Long period comets take a long time to go around Thousands of years Short period comets return every few years Halley’s every 75 to 79 years Last time in 1986 Suspect a nearby star disrupts the Oort cloud to send more comets toward sun.

Asteroids Chunks of planetlike material floating in space Most between Mars and Jupiter Most 1km in diameter Ceres- 1000km in diameter Some pass near Earth Caused craters on moon, and inner planets

Looking for life On other planets Need liquid water and moderate temperatures. Earth is just the right distance to have the right temperatures Looking for evidence of former life on Mars- used to have water. On Titan atmosphere like early earth.

Rockets 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 1000 Tube full of gunpowder with cap on one end.

Escape Velocity The minimum speed needed to leave the gravitational pull. Depends on mass of planet and distance from the center of planet. Earth 11.2 km/sec Moon 2.3 km/sec Jupiter 63.4 km/sec Pluto 0.3 km/sec Sun 616 km/sec

Rockets and Escape Velocity Solid rockets burn up fuel quickly Large thrust early Gravity eventually slows them down. Liquid fuels provide continuous thrust. Goddard- gasoline and liquid oxygen Space shuttle liquid hydrogen and liquid oxygen Multiple stages to reduce weight.

Spacecraft Probes have gone past all the planets except Pluto Have sampled comets tails Have taken pictures of planets and moons.