Chapter 3 The Solar System. How was it formed l The Nebular Theory l Started as nebula about 5 billion years ago – Composed of hydrogen and helium l Nearby.

Chapter 3

The Solar System

How was it formedThe Nebular TheoryStarted as nebula about 5 billion years ago

– Composed of hydrogen and heliumNearby 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 formedOther matter spun around the new sungathered into clumps- protoplanetsNear 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 formedAround 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 JupiterJupiter’s gravity stopped a planet from

formingOort Cloud- Near the edge clumps of

matter- home of comets.

HistoryPeople have used the stars for ages.Used constellations to set planting timesUsed constellations to guide travelsSome lights in the sky wandered through

the constellationsCalled them “planets” which is Greek for

wanderers

PtolemyGreek scientistPlaced earth at center of universeOther objects moved in orbits around the

earthBecause circle was considered a perfect

shape, thought they moved in circular paths

CopernicusPolish astronomerFound Earth and planets revolved around

sun In the same directionAt different speedsThought the orbits were circular

KeplerGerman mathematician and astronomerUsed others observations (Tycho Brahe)Calculated the orbits of planets were

ovals or ellipsesCloser to the sun - shortest time of orbitFarther from the sun - greater time

PlanetsMove in an elliptical orbit

PlanetsPeriod of revolution the time it takes to go once around the

sunone yearMercury 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 directionWhy do they curve?Gravity pulls them toward the sun

What keeps them there?

Inertia

Gravit

y

RotationPlanets spin on their axesOne rotation is a dayMercury 58 days, Jupiter 10 hours

Special Features of the PlanetsMercury

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

MarsRed planet- covered by

iron oxide (rust)Mons Olympus - Largest volcano in the

solar systemTwo ice caps

– north - water -never melts– south -carbon dioxide

melts in summer

Two moons of Mars

PhobosDeimos

Jupiter

JupiterLargest of the gas giantsHuge storms - red spotSmall solid coreLiquid metal layer makes a huge

magnetic fieldMagnetosphereGives off more heat than it receives from

the sunThin ring

JupiterGives off more heat than it receives from

the sun.By far the largest planet.

16 moons 4 seen by Galileo

helped change science

SaturnSimilar to JupiterClouds, magnetosphere, gives off heatRotates in 10 hours - makes it bulge in

the middle and flat at the polesLow density- would float in water

SaturnMany rings

– complex system– made of water– weave in and

out

SaturnMany moons - Titan- the largest is

like the early Earth.

UranusTwice as far from the

sun as Saturn.Covered with ocean

of superheated water

Tilted on axisRings of methane

iceMany moons

NeptuneLike UranusHydrogen and

helium atmosphere

Surface of water and methane

Rings made of dust

Eight moons

TritonLarge moonThought to be

capturedRetrograde

revolutionout of plane of

Neptune’s rotation

PlutoMoon sizedMade of methane Pink atmosphere on the sunny sideMoon Charon 1/2 the size of PlutoScientists think it is a moon broken away

from Neptune– Orbit crosses Neptune– Orbit not in plane with other planets

Other StuffMeteor- the shooting star -the light you

see the skyMeteoroid- solid rocky objects circling the

sunMeteorite- When a meteor hits the groundMost don’t because they burn up in the

atmosphereSome meteoroids are iron and nickelSome are stonyOthers are combinations

MeteoritesLeave a crater where they hit the groundMeteorite Crater in ArizonaEvidence of meteorites from the moon

and from Mars

CometsChunks of dust and gas from the Oort

Cloud that orbit the sunWhen it gets close to the sun it gets

hotterSome of the gas and dust form a cloud

around the head called the comaSolar wind pushes the gases away from

the sun and make the tailTail is pushed by the solar windTail always points way from the sun

Solar wind

Nucleus

Coma

Tail

CometsComets orbit the sunLong 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.

AsteroidsChunks of planetlike material floating in

spaceMost between Mars and JupiterMost 1km in diameterCeres- 1000km in diameterSome pass near EarthCaused craters on moon, and inner

planets

Looking for lifeOn other planetsNeed liquid water and moderate

temperatures.Earth is just the right distance to have the

right temperaturesLooking for evidence of former life on

Mars- used to have water.On Titan atmosphere like early earth.

RocketsRely 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 VelocityThe 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 oxygenMultiple stages to reduce weight.

SpacecraftProbes have gone past all the planets

except PlutoHave sampled comets tailsHave taken pictures of planets and

moons.