Chapter 8 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.
The Origin of the Moon Giant Impact Hypothesis A very large body crashed into the Earth. Debris from the impact made a moon.
4.6 byr ago -- Moon formed, possibly due to collision of Earth and a large, Mars-sized object. • If Earth already differentiated, most material expelled would be mantle material, not iron core
Rock at impact heated, losing volatile elements • Some debris falls back to Earth, some forms Moon. • Earth and Moon each pulled back into spherical shape by gravity.
Why Do We Think This? • The moon has no iron • Earth’s iron had already concentrated in the core by the time of the impact • The iron core of the impactor melded with that of the Earth, leaving the moon with no iron of its own • The moon and Earth share isotopes of oxygen that are not found on other planets or objects far from Earth
Surface Features on the Moon Two types of Surfaces • Highlands • More heavily cratered surface is older. • Maria (“Seas”) • Less heavily cratered surface is younger.
What causes tides? 2 Bulges from Gravitational Attraction & Centrifugal Force
Gravitational Attraction • All masses are drawn to each other. • The moon because of its closeness to the Earth exerts a greater gravitational effect on the Earth than the Sun, despite the fact that the Sun is much more massive than the Moon.
Centrifugal Force • unequal masses of Earth and Moon • center of rotation lies beneath the Earth’s surface. • second tidal bulge • ocean shifts away from center of rotation
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 • 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
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
The Sun • An average star • Over 1 million earth’s would fit inside • 1/4 the density of the Earth • made of 4 layers
Corona- Outermost layer • Temp-1,700,000ºC • Few particles Chromosphere- middle of atmosphere • Temp-27,800ºC • 1000’s of km thick
Photosphere- • Temp-6000ºC • 550 km thick • Surface of the sun Core- 1,000,000ºC 15,000,000ºC
Activity on the Sun • Storms on the sun • Prominences- Loops or arches of gas that rise from the chromosphere • Solar Flares- Bright bursts of light, huge amounts of energy released • Sunspots- Dark areas on the suns surface • in the lower atmosphere • Motion shows the rotation of the sun • Interferes with radio
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