Download CH .20 The Solar System I. Observing the solar system – sun

CH .20 The Solar System
I. Observing the solar system – sun, planets, minor planets, comets, asteroids, + metiors
A. Ancient astronomers – Greeks
1. all stars move together through sky
2. planets – looked like stars that wandered in relation to other stars
3.geocentric system – Earth center of universe, all other objects orbit
Earth
a. Ptolmey – explained star and planet motion
1) ideas believed true for next 1400 years
B. Copernicus – early 1500’s – heliocentric system – sun center of solar system,
all planets orbit sun
1. Galileo’s observations in 1600’s support heliocentric system
2. Kepler discovers planet orbits are ellipses – oval shaped
C. Gravity and inertia maintain orbits
1. inertia – more massive objects are harder to stop or turn direction
a. keeps planets moving forward in orbit
2. gravity – more mass and less distance cause more gravitational pull
a. pulls planets toward the sun, causing curved orbit of planets
II. The Sun – the star we orbit
A. Interior of Sun
1. core – center of sun
a. high temp. and pressure enables nuclear fusion
1) nuclear fusion – hydrogen atoms smash together to
make helium
a) some mass turns into energy in the form of heat
and light
2. sun is about 5 billion years old, and should have enough fuel to burn
another 5 billion years
B. Sun’s Atmosphere – has 3 layers
1. photosphere – inner layer outside of core – makes light
2. chromosphere – middle layer
a. can be seen as red layer during an eclipse
3. corona – outer layer – looks like a halo
a. solar winds – electrically charged particles sent out of sun
1) bad for health
2) blocked by Earth’s atmosphere
3) causes auroras – northern lights
C. Features of Sun
1. sunspots – dark spots on surface of sun caused by cooler gas
a. may influence weather on Earth
2, prominences – reddish arches of gas connecting sun spots
3. solar flares – explosions from sun surface
a. increase solar wind
b. can damage or interfere with satellites
III. Inner Planets – small with rocky surfaces – called terrestrial planets
A. Mercury, Venus, Earth, and Mars
1. Earth – only planet with liquid water
a. 3rd from Sun
2. Mercury – closest to Sun
a. about size of Earth’s moon
b. has no moons of its own
c. greatest range of temperatures
3. Venus – 2nd planet
a. about same size as Earth
b. retrograde roatation – a day (8 Earth months) is longer than a
year (7.5 Earth months)
c. thick atmosphere
1) 90 times pressure on Earth
2) made of carbon dioxide and sulfuric acid clouds
3) hottest planet due to greenhouse effect
4. Mars – 4th planet
a. thin atmosphere – mostly CO2
b. 2 small moons
c. evidence of water and volcanoes in past on surface
IV. Outer Planets – Jupiter, Saturn, Uranus, Neptune
A. are gas giants – much larger than Earth and no solid surface
1. high mass leads to high gravity which holds lots of gas into thick
atmospheres
a. composed of mostly hydrogen and helium like the sun
2. solid cores – not much known
B. Jupiter – largest planet, 5th from Sun
1. red spot – a large storm
2. many moons
a. 1st to be discovered – by Galileo
b. Io – has volcanoes – most geologically active moon in solar
system
c. Europa – Ice surface with water gysers – may contain life
C. Saturn – 2nd largest planet
1. Many rings – largest and most visible of all planetary rings
a. all gas giants have some rings
b. made of ice and small rock
2. moons
a. Titan – largest moon in solar system
D. Uranus – twice as far from Sun as Saturn
1. not Discovered until 1781 by Herschel
2. rotates sideways
3. many moons
E. Neptune – discovered 1846
1. has visible clouds
2. many mons – one has ice caps and dark mineral eruptions
V. Dwarf Planets – new classification in 2006
A. very small planets that have not cleared their orbits of large debris
2B 5 currently recognized – including Pluto and Eris
1. may be thousands more undiscovered
2. many located in the Kuiper Belt – area beyond Neptune – not well
explored
1) not much light that far from Sun to see
VI. Comets, Asteroids, and Meteors
A. Comets – dirty snowballs with long narrow orbits (diagram)
1. more visible when near sun
a. ice turned to gas, which reflects sunlight as a “tail”
b. solar wind blows tail away from sun
2. Classifications
a. short period comets – originate in Kuiper Belt
b. long period comets – originate in Oort Cloud (area outside
Kuiper Belt to half way to nearest star)
B. Asteroids – large chunks of rock orbiting sun
1. asteroid belt – between Mars and Jupiter where most asteroids orbit
2. some asteroid have strange orbits and occasionally collide with planets
a. cused dinosaur extinction 65 million years ago
C. Meteors – chunks of small rock and dust that burn up and make a bright
streak when they enter Earth’s atmosphere
1. meteorite – meteor that hits Earth
a. often made of iron and nickel, so heavy
VII. Life beyond Earth – extraterrestrial - most astronomers think it is very likely
A. Goldilocks planets – have right conditions for possible life
1. liquid water and moderate temperature
2. Kepler satellite telescope searching - has found several so far
a. may be millions in galaxy