Chapter 23Chapter 23Our Solar SystemOur Solar System

23.1 The Solar System23.1 The Solar System From Earth, other planets are just dots of lightFrom Earth, other planets are just dots of light

– Tend to be mistaken for starsTend to be mistaken for stars– Telescopes & space probes revealed so Telescopes & space probes revealed so

much moremuch more Early Ideas about the Solar SystemEarly Ideas about the Solar System

– Earth Center Theory:Earth Center Theory:Early Greeks believed Earth was the Early Greeks believed Earth was the

Center of the UniverseCenter of the UniverseAll objects were imbedded in circular All objects were imbedded in circular

paths around uspaths around us– Their order of the universe:Their order of the universe:

EarthEarth Moon Moon Sun Sun Mercury Mercury Venus Venus Mars Mars JupiterJupiter Saturn Saturn Stars Stars

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Heliocentric ModelHeliocentric Model

1543: Nicholas Copernicus (Polish Astronomer)1543: Nicholas Copernicus (Polish Astronomer)– Proposed a series of different views:Proposed a series of different views:

The Earth is a planetThe Earth is a planetThe moon revolves around the EarthThe moon revolves around the EarthPlanets revolve around the SunPlanets revolve around the SunThe apparent movement of the sun & The apparent movement of the sun &

planets is due to Earth rotating on it’s axisplanets is due to Earth rotating on it’s axis– Galileo Galilei supported CopernicusGalileo Galilei supported Copernicus

Showed Venus goes through phases just like Showed Venus goes through phases just like the moonthe moon

Only possible if Venus orbits the sun Only possible if Venus orbits the sun

Modern View of the Solar SystemModern View of the Solar System 10 Planets revolve around our Sun10 Planets revolve around our Sun

– Mercury, Venus, Earth, MarsMercury, Venus, Earth, Mars– Asteroid belt (separates inner & outer Planets)Asteroid belt (separates inner & outer Planets)– Jupiter, Saturn, Uranus, Neptune, Pluto, XenaJupiter, Saturn, Uranus, Neptune, Pluto, Xena

Most planets have at least one moon orbiting Most planets have at least one moon orbiting themthem

The sun containsThe sun contains 99.86 %99.86 % of all solar system of all solar system massmass

Gravity controls motion and orbital pathsGravity controls motion and orbital paths

Formation of the Solar SystemFormation of the Solar System 5 b.y.a. large cloud of gas, ice & dust existed5 b.y.a. large cloud of gas, ice & dust existed Began to contract & slowly rotateBegan to contract & slowly rotate

– Contraction increased density & rotationContraction increased density & rotation– Gravity began to pull material toward the centerGravity began to pull material toward the center– Density increases = increased rotation & gravityDensity increases = increased rotation & gravity– Begins to form disk with large centerBegins to form disk with large center– Central mass begins to heat up due to contractionCentral mass begins to heat up due to contraction

Temperatures reach 10 million Temperatures reach 10 million 00CC Hydrogen atoms begin to fuse together forming Hydrogen atoms begin to fuse together forming

HeliumHelium Fusion occurs, driving the formation of our SunFusion occurs, driving the formation of our Sun

– The material outside the central mass forms planetsThe material outside the central mass forms planets

This is known as the This is known as the BIG BANG THEORYBIG BANG THEORY

The Parts of Our Solar SystemThe Parts of Our Solar System The sun is the center of the Solar SystemThe sun is the center of the Solar System

– Inner Planets:Inner Planets: First four planetsFirst four planets Solid, rock like structuresSolid, rock like structures

– Asteroid belt:Asteroid belt: band of rocks orbiting the sunband of rocks orbiting the sun

– Outer Planets:Outer Planets: Six planets farthest from the Six planets farthest from the sunsun

4 are made up of mainly lighter element gases4 are made up of mainly lighter element gases Last two are frozen materialsLast two are frozen materials

Motion of the PlanetsMotion of the Planets Johannes KeplerJohannes Kepler studied planetary orbitsstudied planetary orbits

– Discovered orbits areDiscovered orbits are elliptical elliptical Farther from the sun, larger the ellipseFarther from the sun, larger the ellipseRealized the Sun is not exactly central in Realized the Sun is not exactly central in

our solar systemour solar system– Planets travel at different speeds through Planets travel at different speeds through

their orbittheir orbitPlanets closer to the sun move fasterPlanets closer to the sun move fasterPlanets change speed during their orbit Planets change speed during their orbit

as wellas well

23.2 The Inner Planets23.2 The Inner Planets

Called Called Terrestrial PlanetsTerrestrial Planets– First four planets: First four planets: MercuryMercury, , VenusVenus, , EarthEarth, ,

MarsMars– All have a solid crust surfaceAll have a solid crust surface– Most have an atmosphere of some kind Most have an atmosphere of some kind – Most have at least one moonMost have at least one moon

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Mercury:Mercury: Closest planet to the SunClosest planet to the Sun

– Revolution time:Revolution time: 88 days88 days– Rotation time:Rotation time: 59 days59 days

Third smallest planetThird smallest planet Probed by Probed by Mariner 10 (1974-1975)Mariner 10 (1974-1975)

– Imaged 45% of surfaceImaged 45% of surface– Surface crater riddled (similar to our Moon)Surface crater riddled (similar to our Moon)– Has large cliff lined valleysHas large cliff lined valleys– Has a weak magnetic field (indicates iron core)Has a weak magnetic field (indicates iron core)– Very thin atmosphere: Very thin atmosphere:

Hydrogen, Helium, Sodium & PotassiumHydrogen, Helium, Sodium & Potassium– Surface Temperature:Surface Temperature:

Daytime: 842 Daytime: 842 ooFFNight: -274 Night: -274 ooFF

Venus:Venus: Second planet from the sunSecond planet from the sun

– Revolution: 255 daysRevolution: 255 days– Rotation: Retrograde = spins backwardsRotation: Retrograde = spins backwards– Probed by Venera (Russian) in 1970Probed by Venera (Russian) in 1970– Probed by Magellan (US) in 1990 to 1994Probed by Magellan (US) in 1990 to 1994

““Earth’s Twin Sister”Earth’s Twin Sister”– Size, Mass, Gravity similar to EarthSize, Mass, Gravity similar to Earth

Atmosphere: Thick & toxicAtmosphere: Thick & toxic– Air Pressure = 90 times that of EarthAir Pressure = 90 times that of Earth– Mostly carbon dioxideMostly carbon dioxide– Clouds: Rain sulfuric acidClouds: Rain sulfuric acid– Only allow 2% of sunlight through to surfaceOnly allow 2% of sunlight through to surface

Solar energy trapped = extreme Greenhouse EffectSolar energy trapped = extreme Greenhouse Effect Surface temperature = 878 Surface temperature = 878 ooFF

– Surface covered by craters, fault lines, & VolcanoesSurface covered by craters, fault lines, & Volcanoes– Winds = 300 km / hr.Winds = 300 km / hr.

Earth:Earth: ““Third Rock from the Sun”Third Rock from the Sun” Average distance from the sun = Average distance from the sun =

93,000,000 miles93,000,000 miles Only planet water exists as 3 states of Only planet water exists as 3 states of

mattermatter– Solid, Liquid, & GasSolid, Liquid, & Gas

Atmosphere protects the planetAtmosphere protects the planet– From meteor strikes (most burn up)From meteor strikes (most burn up)– Intense Solar Radiation (UV, X-Rays, Intense Solar Radiation (UV, X-Rays,

Gamma Rays, etc.)Gamma Rays, etc.)

Mars:Mars: Fourth Planet from the Fourth Planet from the

SunSun ““The Red PlanetThe Red Planet”” Surface mainly iron Surface mainly iron

oxide dust (Rust)oxide dust (Rust) Revolution time: 687 Revolution time: 687

daysdays Has polar ice capsHas polar ice caps

– Northern: frozen Northern: frozen Water (HWater (H22O)O)

– Southern: frozen Southern: frozen Carbon Dioxide (COCarbon Dioxide (CO22))

Discoveries on MarsDiscoveries on Mars Mariner 9Mariner 9 (1971–1972) (1971–1972)

– Discovered dried riverbedsDiscovered dried riverbeds– Olympus Mons:Olympus Mons: Largest know volcano in the Solar Largest know volcano in the Solar

SystemSystem– Rift Zones: Deep crustal tearsRift Zones: Deep crustal tears

Viking 1 & 2 (1976)Viking 1 & 2 (1976)– Each consisted of Orbiter & LanderEach consisted of Orbiter & Lander– Photographed entire Martian surface (Orbiters)Photographed entire Martian surface (Orbiters)– Studied meteorological, chemical, & biological Studied meteorological, chemical, & biological

aspectsaspects Discovered barren, rocky, windswept surfaceDiscovered barren, rocky, windswept surface Atmosphere: very thin; Carbon Dioxide, Nitrogen Atmosphere: very thin; Carbon Dioxide, Nitrogen

& Argon& Argon Surface Temperatures: 95Surface Temperatures: 95ooF (day) to -274 F (day) to -274 ooF F

(night) (night) Temperature changes create intense winds & Temperature changes create intense winds &

dust stormsdust storms NO evidence of life (past or present)NO evidence of life (past or present)

Martian MoonsMartian Moons Mars has small, crater riddled moonsMars has small, crater riddled moons

– 1)1) Phobos: Phobos: 25 km in diameter 25 km in diameter Slowly spiraling toward MarsSlowly spiraling toward Mars Expected impact of surface in 50 million yearsExpected impact of surface in 50 million years

– 2) 2) Deimos:Deimos: 13 km in diameter 13 km in diameter Both are irregularly shapedBoth are irregularly shaped Both orbit Mars several times a dayBoth orbit Mars several times a day

23.3 Mission to Mars23.3 Mission to Mars How should Mars be explored?How should Mars be explored?

– Travel time to Mars is a considerationTravel time to Mars is a consideration Orbits at their closest = 1.5 years travel timeOrbits at their closest = 1.5 years travel time Orbits at their farthest = over 5 years travel timeOrbits at their farthest = over 5 years travel time

– Length of travel time invites great risks to humansLength of travel time invites great risks to humans Should humans explore Mars?Should humans explore Mars?

– Humans do more meticulous & detailed work than Humans do more meticulous & detailed work than probesprobes

– Zero gravity travel weakens muscles & bonesZero gravity travel weakens muscles & bones– Body fluids move upward (increase kidney function)Body fluids move upward (increase kidney function)– Radiation exposure drastically increasedRadiation exposure drastically increased

Should robots explore Mars?Should robots explore Mars?– Robots aren’t affected by 0 G’s; travel time not a Robots aren’t affected by 0 G’s; travel time not a

factorfactor– Robots using videotronics can be controlled from Robots using videotronics can be controlled from

EarthEarth Signals can have up to 20 min. delaySignals can have up to 20 min. delay Robots cannot improvise & adapt to changing Robots cannot improvise & adapt to changing

situations situations

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23.4 The Outer Planets23.4 The Outer Planets 4 planets are gaseous giants4 planets are gaseous giants ( (Jovian Jovian

PlanetsPlanets)) Last 2 are frozen spheresLast 2 are frozen spheres

– Voyager 1 & 2 probed the 4 gaseous giantsVoyager 1 & 2 probed the 4 gaseous giants Jupiter, Saturn, Uranus, NeptuneJupiter, Saturn, Uranus, Neptune

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Jupiter:Jupiter: Largest Planet in our Solar SystemLargest Planet in our Solar System Fifth planet in orderFifth planet in order Revolution = 11.9 years to orbitRevolution = 11.9 years to orbit Rotation = 10 hrs. (fastest of all planets)Rotation = 10 hrs. (fastest of all planets) Voyager 1 & 2 (1979) probed JupiterVoyager 1 & 2 (1979) probed Jupiter

– Gathered information about Jupiter’s Moons’ Gathered information about Jupiter’s Moons’ AtmospheresAtmospheres

– Discovered 3 more moonsDiscovered 3 more moons– Discovered a faint dust ring orbiting JupiterDiscovered a faint dust ring orbiting Jupiter

Jupiter’s Composition: Jupiter’s Composition: – Hydrogen, Helium, Ammonia, Methane, & water vaporHydrogen, Helium, Ammonia, Methane, & water vapor– Gaseous Atmosphere, Liquid Mantle, & Solid CoreGaseous Atmosphere, Liquid Mantle, & Solid Core– Clouds form color bands; Winds up to 400 km/hr.Clouds form color bands; Winds up to 400 km/hr.

– Great Red SpotGreat Red Spot: : ContinuousContinuous Atmospheric Storm Atmospheric Storm

– Lightning has been observed in the atmosphereLightning has been observed in the atmosphere – Radiates 2x as much heat as it receivesRadiates 2x as much heat as it receives– Believed to be a star “that just didn’t make it”

Jupiter’s MoonsJupiter’s Moons Jupiter has at least 16 moons

– Four Largest = Galilean Moons (Discovered in 1610)

Io, Europa, Ganymede, Callisto– Io: Closest of the Large moons to Jupiter

Most volcanic objects in out Solar System Sulfuric Lava produces Reddish/Orange color Holds a thin sulfur dioxide atmosphere

– Europa: Composed of solid rock covered with ice Tectonic activity Thin oxygen atmosphere

– Ganymede: Largest moon in the Solar System Larger than Mercury, Surface covered in Ice Slushy Mantle, Solid rock core

– Callisto: Composed of heavily cratered Rock/Ice Crust

Water/Ice mantle with a rocky core

Galilean MoonsGalilean MoonsIo with eruption Europa

Ganymede Callisto

Saturn:Saturn: Sixth planet; 30 year orbit; 11 hr rotationSixth planet; 30 year orbit; 11 hr rotation 1980 & 1981 surveyed by the Voyagers1980 & 1981 surveyed by the Voyagers

– ““Ringed Planet”Ringed Planet”– Second Largest planetSecond Largest planet– Very low density (would float in water)Very low density (would float in water)

Atmospheric composition:Atmospheric composition:– Mostly hydrogen & helium; also ammonia, methaneMostly hydrogen & helium; also ammonia, methane– Liquid Hydrogen/helium mantleLiquid Hydrogen/helium mantle– Small rocky coreSmall rocky core

Rings composed of 100’s of ringletsRings composed of 100’s of ringlets– Ringlets are made up of ice & rock particlesRinglets are made up of ice & rock particles

At least 18 moon orbit Saturn (Most of any planet)At least 18 moon orbit Saturn (Most of any planet)– Largest moon = Titan (2Largest moon = Titan (2ndnd largest in Solar System) largest in Solar System)

Real atmosphere of nitrogen, argon, & methaneReal atmosphere of nitrogen, argon, & methane Thick, smog clouds cover TitanThick, smog clouds cover Titan Surface temp. = -180 Surface temp. = -180 00C (-292 C (-292 ooF)F)

Uranus:Uranus: Smallest of the gas planets Smallest of the gas planets Discovered in 1781Discovered in 1781 77thth planet, 84 year orbit, 17 hour rotation ** planet, 84 year orbit, 17 hour rotation ** Average Temp. = -328Average Temp. = -328ooFF Voyager 2 surveyed (1986)Voyager 2 surveyed (1986)

– Discovered 10 unknown moons (making 15 total)Discovered 10 unknown moons (making 15 total) 5 largest almost identical5 largest almost identical Dark color, lack atmosphere, crater riddledDark color, lack atmosphere, crater riddled

– Discovered several dark ringsDiscovered several dark rings– Detected a magnetic field tilted 60Detected a magnetic field tilted 6000 from axis from axis– Atmosphere: Hydrogen, Helium & MethaneAtmosphere: Hydrogen, Helium & Methane

Methane gives planet a blue/green tintMethane gives planet a blue/green tint Liquid mantle of water, methane, & Liquid mantle of water, methane, &

ammoniaammonia Rocky coreRocky core

– ** Rotational axis lays on its side ** Rotational axis lays on its side (spins like a tire)(spins like a tire)

Neptune:Neptune: Last of the gas planets; discovered in 1846Last of the gas planets; discovered in 1846 Orbit overlaps Pluto’s at 2 pointsOrbit overlaps Pluto’s at 2 points

– Change position 8 Change position 8 9 & 9 9 & 9 8 8– 1 orbit = 165 years; 1 rotation = 16 hrs1 orbit = 165 years; 1 rotation = 16 hrs

Atmosphere: Hydrogen, Helium, MethaneAtmosphere: Hydrogen, Helium, Methane– Methane gives Neptune bluish tint Methane gives Neptune bluish tint – Winds = 2200 km/hr; Temperature = -417 Winds = 2200 km/hr; Temperature = -417 00FF– Has a dark spot = storm in it’s atmosphereHas a dark spot = storm in it’s atmosphere– Liquid mantle: water, methane, & ammoniaLiquid mantle: water, methane, & ammonia– Core: solid rockCore: solid rock

Voyager 2 detected 6 moons (Totaling 8)Voyager 2 detected 6 moons (Totaling 8)

– Largest moon = Largest moon = TritonTriton Has a thin nitrogen atmosphereHas a thin nitrogen atmosphere Constantly erupting methane geysersConstantly erupting methane geysers

– Neptune also has rings (thin & thicken at different places)Neptune also has rings (thin & thicken at different places)

Pluto:Pluto: Discovered in 1930; smallest planetoidDiscovered in 1930; smallest planetoid Between 1979 & 1999 Pluto orbited inside NeptuneBetween 1979 & 1999 Pluto orbited inside Neptune

– Rest of the time the ninth planetRest of the time the ninth planet– Orbit = 248 yearsOrbit = 248 years– Has a different orbital plane (tilted 17Has a different orbital plane (tilted 1700 from other from other

planets)planets) Surrounded by a minimal atmosphereSurrounded by a minimal atmosphere

– Temperature = -364 Temperature = -364 ooFF Solid rocky crustSolid rocky crust One Moon, Charon (½ diameter of Pluto)One Moon, Charon (½ diameter of Pluto)

– Orbits very close to PlutoOrbits very close to Pluto– Sometimes considered “a double planet” with PlutoSometimes considered “a double planet” with Pluto

Xena:Xena:

Discovered January 8Discovered January 8thth, 2005, 2005– 20 % larger than Pluto20 % larger than Pluto– Orbital time unknown; Orbital time unknown;

Rotational time unknownRotational time unknown– Has one known moonHas one known moon– Dark & cold (below -225 Dark & cold (below -225 00C C

or -373 or -373 ooF)F)– Has not been “officially” Has not been “officially”

named yetnamed yet

Kuiper BeltKuiper Belt Discovered by the Hubble TelescopeDiscovered by the Hubble Telescope Vast disk of icy cometsVast disk of icy comets Located near Neptune’s orbitLocated near Neptune’s orbit

Voyagers’ Continuing MissionVoyagers’ Continuing Mission After passing Saturn in 1980 Voyager 1 After passing Saturn in 1980 Voyager 1

headed out of our Solar Systemheaded out of our Solar System After passing Pluto in 2000 Voyager 2 After passing Pluto in 2000 Voyager 2

headed out of our Solar Systemheaded out of our Solar System Both are still transmitting information back Both are still transmitting information back

to Earth about deep space, and our sun’s to Earth about deep space, and our sun’s long range influence of charged particleslong range influence of charged particles

23.5 Other Solar System Objects23.5 Other Solar System Objects Comets:Comets:

– Controlled by a star’s gravityControlled by a star’s gravity– Travel through planets’ orbits, out of the Solar Travel through planets’ orbits, out of the Solar

System, & back in againSystem, & back in again

– HALLEY’S COMET:HALLEY’S COMET: Most famous (last seen Most famous (last seen 1986)1986)

Returns every 76 yearsReturns every 76 years Will return in 2062Will return in 2062

– HALE-BOPP:HALE-BOPP: Most recent cometMost recent comet Discovered in July 23, 1995Discovered in July 23, 1995 Visible from Earth during 1997Visible from Earth during 1997

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Halley’s CometHale-Bopp Comet

Comet Information:Comet Information: Comet Composition: Comet Composition:

– Dust, rock, frozen methane, ammonia, and waterDust, rock, frozen methane, ammonia, and water– Comets normally look like dirty snowballsComets normally look like dirty snowballs– When they get close to stars, they changeWhen they get close to stars, they change

They begin to vaporize & GlowThey begin to vaporize & Glow Forms aForms a comacoma (tail) from the(tail) from the nucleusnucleus (head)(head)

– Coma:Coma: glowing trail of particles glowing trail of particles – Always points away from the starAlways points away from the star

– Comets eventually break up into space debrisComets eventually break up into space debris Oort Cloud:Oort Cloud: large collection of comets beyond large collection of comets beyond

PlutoPluto

Meteoroids, Meteors, & MeteoritesMeteoroids, Meteors, & Meteorites

Meteoroids:Meteoroids: chunks of rockchunks of rock– Randomly moving through spaceRandomly moving through space– Usually leftover comet or asteroid debrisUsually leftover comet or asteroid debris

Meteor:Meteor: Meteoroid that enters Earth’s Meteoroid that enters Earth’s atmosphereatmosphere– Heat up & begin to glow = shooting starHeat up & begin to glow = shooting star– Most burn up before reaching the surfaceMost burn up before reaching the surface– Many meteors at one time = meteor Many meteors at one time = meteor

showershower Meteorite:Meteorite: Meteor that does not totally burn Meteor that does not totally burn

up, & strikes the Earth’s surfaceup, & strikes the Earth’s surface– Impact creates a craterImpact creates a crater

LARGEST METEORITE TO HIT LARGEST METEORITE TO HIT EARTH – Namibia, AfricaEARTH – Namibia, Africa

Largest US Meteorite – Kansas Largest US Meteorite – Kansas under 6 feet of earth.under 6 feet of earth.

AsteroidsAsteroids Large rocks located between Mars & JupiterLarge rocks located between Mars & Jupiter

– Asteroid belt: Large orbiting ring of asteroidsAsteroid belt: Large orbiting ring of asteroids– Believed to be a planet that never formedBelieved to be a planet that never formed– Range in size from dust to Moon sizeRange in size from dust to Moon size

Some Named Asteroids:Some Named Asteroids:– Ceres: 940 km (Largest known)Ceres: 940 km (Largest known)– Pallas: 523 kmPallas: 523 km– Vesta: 501 kmVesta: 501 km– Juno: 244 kmJuno: 244 km– Gaspra & Ida: Gaspra & Ida: – Photographed by Galileo probePhotographed by Galileo probe– Ida even has a smaller asteroid orbiting itIda even has a smaller asteroid orbiting it