The Solar System Chapter 2 2-1 The Solar System Evolves • Solar system began about 5 billion years ago – Changing ever since – Began as a cloud of dust and gases – Very cold • Solar system consists of the following: – Sun – Planets – Other objects that revolve round the sun • Nebular Theory – the solar system began as a huge cloud of dust and gas called a nebula, which later condensed to form the sun and its 9 planets The Sun forms First • Nebula, which solar system formed, primarily of Hydrogen and Helium • Planets contain a wide variety of gases • Star exploded in a supernova – Sending heavy metals into space – Seeded themselves into nebula – Nebula began to collapses, causing it to spin faster, flattening out with a protosun forming in the middle – As nebula continued to collapse protosun grew larger – Over millions of years gravitational forces caused Hydrogen atoms to fuse and form Helium – Gave off great heat and light causing a star to be born – The Sun The Planets Form • Gases continued to spin around the sun • Gravity caused for some gases to clump together, growing larger over time • Protoplanets – early stages of planets – Those near sun got so hot that lightweight gases, Hydrogen & Helium boiled away – Collections of rocky material and metals – Mercury, Venus, Earth, Mars • Protoplanets farther from sun maintained gases and grew to enormous sizes • Jupiter, Saturn, Uranus, Neptune • As planets cooled over time smaller clumps formed around them becoming satellites and moons • Astronomers believed a satellites broke away from Neptune and became known as Pluto • Small clumps exist known as Asteroids (rocklike objects) – Asteroid Belt found between Mars & Jupiter 2-2 Motions of the Planets • Planets got name from the Greeks meaning “wanderers” Earth at the Center? • Ptolemy – Greek scientist, proposed that the Earth was at the center of universe – All objects travelled in orbits around Earth, which didn’t move – Orbit – path 1 object takes when moving around another object in space – Orbits were perfect circles – Universe was unchangeable – Ptolemy’s theory held to be true for over 1400 years Sun at the Center? • Nicolaus Copernicus – Polish astronomer developed a theory that the Earth and other objects revolved around the sun • All planets revolve around sun in same direction • Each planet took different amt of time to revolve around sun • Also believed orbits were perfect circles Elliptical Orbits • Johannes Kepler – German mathematician and astronomer, supported Copernicus’ theory – Found that paths of planets were not perfect circles but elliptical in shape (oval or egg-shaped) – Kepler was correct – Planets travel in a counterclockwise elliptical orbit around the sun – Planets closest to the sun travel the shortest distance taking less time to orbit Inertia and Gravity • Sir Isaac Newton – English scientist explained why the planets stayed in motion instead of shooting off into space – Law of Inertia – a moving object will not change speed or direction unless an outside force causes a change in its motion – Sun’s gravitational pull was the force acting on the planets • Inertia and Gravity are 2 factors that keep planets in motion around the sun – Inertia causes planets to move in straight line – Gravity pulls planets toward sun – Combined cause an elliptical motion Period of Revolution • Period of Revolution – time it takes planet to make 1 revolution around the sun – Period of revolution is it’s year – The closer the planet is to the sun the shorter it’s year – Mercury’s year = 88 days – Earth’s year = 365 days – Pluto’s year = 90,520 days Period of Rotation • All planets spin/rotate on it’s axis – Axis – imaginary line that runs through the center of a planet – Period of Rotation – time it takes planet to rotate 1 time on it’s axis – Earth’s rotation = 24 hours or 1 day – Mercury’s rotation = 59 Earth-days (1416 hours) – Pluto’s rotation = 6 Earth-days (144 hours) 2-3 A Trip Through the Solar System • There are 9 planets in our Solar System – Each has unique surface and atmosphere – See page 68-69 Mercury – Faster that a Speeding Bullet • • • • • • Closest planet to the sun Little to no atmosphere, no weather No change to surface from billions of years prior Revolves around the sun in 88 days at 48 km/sec Named after the speedy messenger Roman god 1975 United States sent Mariner 10 to explore – Crater-covered world – Craters scooped out about 10 billion years ago from pieces of material striking the planet – Long steep cliffs, some hundreds of km across • Mercury rotates on its axis very slow – 59 Earth days for 1 rotation – Rotates 3 times abt its axis for every 2 revolutions around the sun – Produces a sun rise every 175 Earth days – Temperatures range from 427°C during the day and -170°C at night Venus – Greenhouse in the Sky • Named after Roman goddess of beauty & love • Abt same diameter, density, and mass as Earth – Once called Earth’s twin • Thick cloud cover (more that 5 times as dense as Earth’s clouds) • US spacecraft Pioneer Venus Orbiter and Magellan were placed in orbit and were able to map the surface – Winds more than 350 km/hr – Clouds made of droplets of sulfuric acid and carbon dioxide – Volatile atmosphere, lightning and acid rain – Rapid increase in temperature and pressure (hotter than Mercury) – Pressure is 91 times that on earth • • • • Deep canyons, craters, & vast plains Remains of once active volcanoes Clouds hide surface from sun Sun slowly rises in west and sets in east b/c Venus rotates east to west – Retrograde rotation – reverse motion – Rotates 1 time on it’s axis every 243 Earth-days – Takes 224 Earth-days to revolve 1 time around sun • Day is longer than its year • Scientists believe billions of years ago Venus was covered in vast oceans – Coastlines and dried up sea beds detected – As water evaporated as sun grew hotter as it got older, water vapor became trapped creating a Greenhouse Effect Mars – The Rusty Planet • 4th planet from the sun • Named after the Roman god of war due to its reddish color (blood) • 2 moons circle Mars: Phobos & Deimos • Surface rocky and heavily cratered • Viking 1 & Viking 2 (US spacecrafts) – Landed on Mars – Analyzed Martian soil • Soil is similar to Earth’s • Contains a lot of Iron oxide giving it the reddish color • Has a very active past such as huge volcanoes – Olympus Mons – largest volcano on Mars & Solar System • Wider than Hawaii and 3 times as tall as Mt Everest – When volcanoes were active they poured out lava and steam (steam cooled and fell as rain) – Rushing rivers gouged out channels across Mars – No liquid water found – Frozen water found in Northern Icecaps (never melts) – Southern Icecaps made of frozen carbon dioxide – Melt in summer (only 0°C in summer due to thin atmosphere The Asteroid Belt • Thousands of rocks and “flying mountains” known as “minor planets” – Sweep around sun btwn orbits of Mars and Jupiter Jupiter – Planet that was almost a Star • Named after the Romans king of the Gods • Made primarily of Hydrogen & Helium gases – Similar to the sun • Temperature: 30,000°C in the core – Scientist believe if Jupiter had gotten any larger in the formation of the solar system that it may have undergone nuclear fusion and became a star • Can only see Jupiter’s atmosphere from Earth – Appear as bands of color made of hydrogen & helium • Huge storms swirl the atmosphere of Jupiter • Giant Red Spot – 3 times the size of Earth, is a hurricane-like storm in Jupiter’s atmosphere – Over 20,000 years old • Huge atmospheric pressure due to thick cloud cover • Surface covered by huge Hydrogen oceans – Due to high pressure the liquid Hydrogen acts like a metal that surrounds the core – This layer causes Jupiter’s gigantic magnetic field called the Magnetosphere – Stretches millions of km beyond the planet – Largest single structure in the solar system • Jupiter gives off more heat than it receives from the sun • Voyager 1 & 2 flew past Jupiter in exploration – Discovered a thin ring around it – Enormous lightning bolts in atmosphere – Mysterious shimmering sheets of light in sky • Galileo observed 4 moons orbiting Jupiter – Known as the Galilean satellites – Today more that 16 moons have been discovered • Io – innermost and large moon of Jupiter – Rich in colors of red, yellow, and orange – has a very young surface due to the active volcanoes constantly covering the surface with new material • Europa – ice-covered, smaller that Io – Smooth, bright white surface – Photos show a volcano that appears to spew out water and ammonia ice • Ganymede – largest moon in solar system – Half ice, half rock – Mostly craters • Callisto – most heavily cratered moon in solar system – Took billions of years to create all the craters – Very little activity Saturn – A World of Many Rings • Surrounded by beautiful rings – Made of icy particles – Range in size from .001 mm – 100 km diameter – Farthest ring is 30,000km from planet • Spins very fast on its axis – So fast it flattens at its poles • Made of Hydrogen and Helium gases • Many violent storms and huge lightning storms • Clouds form bands around planet – Bands alternate in color giving off a reddishorange color in its southern hemisphere • Giving off a similar look as Jupiter’s Giant Red Spot – Gives off more heat that it receives from sun – Huge magnetic field – Least dense planet in solar system • Saturn has more moons than any other planet – Titan is its largest moon & surrounded by many deadly gases (hydrogen cyanide, methane, etc) Uranus – A Planet on its Side • Named for the father of Saturn in Roman mythology • Twice as far from sun as Saturn • Gas giant like Jupiter and Saturn – Covered by thick atmosphere of Hydrogen, Helium, & Methane • Greenish in color • Very cold at top of clouds (-220°C) • Uranus’ axis is tilted at a 90° angle – Appears to be tipped on its side • 9 rings made of methane ice surround planet • 15 moons that vary in size Neptune – The Mathematician’s Planet • Roman god of the seas – Named for its bluish color • Altered the orbit of Uranus due to gravitational forces • Neptune & Uranus known as “Twin Giants” – Similar in size, mass, & temperature • Covered by thick clouds of Methane float in a Hydrogen & Helium atmosphere • Voyager 2 discovered Neptune has 5 rings – Made of dust particles formed from meteorites that crashed into Neptune’s moons • 8 moons – Triton – 4th largest moon in solar system • Covered in frozen Methane • Orbits Neptune backward/retrograde Pluto – A Double Planet • Discovered in 1930 by Clyde Tombaugh • Named for Roman god of the Underworld • Smallest and least massive planet in solar system • Been removed from solar system as a planet Comets • Oort Cloud – vast collection of ice, gas, & dust – 15 trillion km from sun – Gravitational pull of a star will pull a “dirty snowball” out and send it speeding toward the sun – Mountain sized object known as a Comet • Nucleus – core of comet • Coma – cloud of gas & dust surrounding nucleus • Nucleus and Coma make up the Head of comet – Gets hotter and larger the closer it gets to sun • Solar winds blow coma outward into a long tail – Streams away from sun – Tail of incoming comet streams out behind it – Tail of outgoing comet streams in front of it • Long period comets orbit the sun over & over again – Long, elliptical orbits, reaching the edge of solar system – Take thousands of years to make 1 orbit • Short period comets return every few years – Halley’s Comet most famous – Returns every 75-79 yrs Meteoroids, Meteors, and Meteorites • Meteoroids – chunks of metal or stone that orbit the sun – Come from Asteroid Belt or comets • Meteor – streak of light produces by a burning meteoroid – Known as “Shooting Stars” – Most burn up in the atmosphere • Meteorite – meteor that survives the atmosphere and strikes the Earth – Composed mainly of Iron, Nickel, and Stone