Formation of the Solar Formation of the Solar SystemSystem

Chapter 19 Chapter 19

Section 3Section 3

Astronomy – A historyAstronomy – A history

The first record of the study of The first record of the study of astronomy was in Nabta, Egyptastronomy was in Nabta, Egypt Group of stones were arranged to line Group of stones were arranged to line

up with the sun on the longest day of up with the sun on the longest day of the year (summer solstice)the year (summer solstice)

Stonehenge, England – one of the Stonehenge, England – one of the world’s oldest observatoriesworld’s oldest observatories Stones are aligned with the winter and Stones are aligned with the winter and

summer solsticesummer solstice

The UniverseThe Universe THE SUM OF ALL SPACE, THE SUM OF ALL SPACE,

MATTER, AND ENERGY THAT MATTER, AND ENERGY THAT EXISTS, THAT HAS EXISTED IN EXISTS, THAT HAS EXISTED IN THE PAST AND THAT WILL EXIST THE PAST AND THAT WILL EXIST IN THE FUTURE.IN THE FUTURE.

Inside of this universe there are Inside of this universe there are galaxies that hold millions of galaxies that hold millions of stars. stars.

We are located in one of these We are located in one of these galaxies…THE MILKY WAY galaxies…THE MILKY WAY GALAXY.GALAXY.

The Milky Way GalaxyThe Milky Way Galaxy

Models of the EarthModels of the EarthHistory of the Universe ModelHistory of the Universe Model

The first models had the Earth in the The first models had the Earth in the center of the solar system – center of the solar system – GEOCENTRICGEOCENTRIC

Greeks were the first to try to Greeks were the first to try to determine Earth’s place in the determine Earth’s place in the universeuniverse

Aristotle used math and models to Aristotle used math and models to illustrate the universeillustrate the universe

Models of the EarthModels of the EarthHistory of the Universe ModelHistory of the Universe Model

Copernicus was the first to put the Copernicus was the first to put the sun in the center of the solar system sun in the center of the solar system (1543) – HELIOCENTRIC(1543) – HELIOCENTRIC

Also explained that the earth and Also explained that the earth and other planets orbited the sun in other planets orbited the sun in perfect circles.perfect circles.

Models of the EarthModels of the EarthHistory of the Universe ModelHistory of the Universe Model

Kepler (1605) – improved on the Kepler (1605) – improved on the Copernicus modelCopernicus model Explained that the orbits are actually Explained that the orbits are actually

ellipses or ovalsellipses or ovals At this time, there was no mathematical At this time, there was no mathematical

proof so it was not considered true.proof so it was not considered true.

Models of the EarthModels of the EarthHistory of the Universe ModelHistory of the Universe Model

Newton (1687) – Explained GravityNewton (1687) – Explained Gravity Helped to explain why the planets Helped to explain why the planets

traveled in elliptical orbits around the traveled in elliptical orbits around the sunsun

Explained that every object in the Explained that every object in the universe exerts a gravitational force on universe exerts a gravitational force on every other object.every other object.

Gravitational ForcesGravitational Forces

Every object in the universe has a Every object in the universe has a gravitational force. gravitational force.

Larger objects have more Larger objects have more gravitational pull compared to gravitational pull compared to smaller objects. smaller objects.

Smaller objects that are close Smaller objects that are close enough to a larger object will ORBIT enough to a larger object will ORBIT the larger object.the larger object.

Formation of the Solar SystemFormation of the Solar SystemThe NEBULAR MODELThe NEBULAR MODEL

This is the most widely accepted This is the most widely accepted model for the formation of the solar model for the formation of the solar system (-p. 648-649)system (-p. 648-649)

NEBULA – A large cloud of dust and NEBULA – A large cloud of dust and gas in space…region where stars are gas in space…region where stars are born or explodeborn or explode

According to this model the sun and According to this model the sun and planets formed from a cloud of gas planets formed from a cloud of gas and dust that collapsed because of and dust that collapsed because of gravity.gravity.

Steps in the Nebular ModelSteps in the Nebular Model 1. Young solar nebula collapses 1. Young solar nebula collapses

due to gravity.due to gravity. 2. Solar nebula begins to rotate, 2. Solar nebula begins to rotate,

flatten, and get warmer near the flatten, and get warmer near the center.center.

3. Small “planetismals” begin to 3. Small “planetismals” begin to formform

4. Larger “planets” begin to 4. Larger “planets” begin to collect dust and gas from the collect dust and gas from the nebula nebula

5. ACRETION – smaller 5. ACRETION – smaller planetismals collide with the planetismals collide with the larger “planets” causing them to larger “planets” causing them to growgrow

6. Remaining dust and gas are 6. Remaining dust and gas are eventually removed…leaving eventually removed…leaving planets around the sunplanets around the sun

7. A NEW SOLAR SYSTEM IS 7. A NEW SOLAR SYSTEM IS FORMED!FORMED!

The Big Bang TheoryThe Big Bang Theory

The theory that all matter and The theory that all matter and energy in the universe was energy in the universe was compressed into an extremely small compressed into an extremely small volume that 10 to 20 billion years volume that 10 to 20 billion years ago exploded and began expanding ago exploded and began expanding in all directions.in all directions.

Red Shift and Blue ShiftRed Shift and Blue ShiftThe Doppler EffectThe Doppler Effect

Based on wavelengths of light.Based on wavelengths of light. Longer wavelengths show red shiftLonger wavelengths show red shift Shorter wavelengths are blue shiftShorter wavelengths are blue shift Red Shift relates to the movement of Red Shift relates to the movement of

objects away from the observer (our objects away from the observer (our universe has red shift so it is believed to universe has red shift so it is believed to be expanding)be expanding)

Blue shift relates to the movement of Blue shift relates to the movement of objects towards the observerobjects towards the observer

GalaxiesGalaxies

Contain millions to billions of starsContain millions to billions of stars Distances between galaxies are Distances between galaxies are

extremely large.extremely large. 3 Types of Galaxies – Spiral, 3 Types of Galaxies – Spiral,

Elliptical, and IrregularElliptical, and Irregular

Spiral GalaxiesSpiral Galaxies

Have spiral arms Have spiral arms made of gas, dust, made of gas, dust, and stars.and stars.

Example: Milky Example: Milky Way GalaxyWay Galaxy

Elliptical GalaxiesElliptical Galaxies

Have no spiral Have no spiral arms and are arms and are egg shaped.egg shaped.

They contain They contain mostly older mostly older stars.stars.

Irregular GalaxiesIrregular Galaxies

Lack regular Lack regular shapes and do shapes and do not have a well-not have a well-defined structuredefined structure

Stars: Life and DeathStars: Life and Death

Chapter 20Chapter 20

StarsStars

A large celestial body that is A large celestial body that is composed of gas and emits lightcomposed of gas and emits light The SUN is a typical star that is just The SUN is a typical star that is just

closer to earth than other starscloser to earth than other stars The Greeks grouped stars into shapes The Greeks grouped stars into shapes

called constellationscalled constellations Core temperature is more than 15 Core temperature is more than 15

million Kelvinsmillion Kelvins

Nuclear Fusion in StarsNuclear Fusion in Stars

Takes place in the core of the starTakes place in the core of the star Combines Hydrogen atoms fusing Combines Hydrogen atoms fusing

together because of high temperature and together because of high temperature and pressurepressure

Energy from fusion is released as radiation Energy from fusion is released as radiation and convection through the star layersand convection through the star layers

Light travels at 3 x 10Light travels at 3 x 1088 m/s m/s From the sun to the earth it takes 8 minutesFrom the sun to the earth it takes 8 minutes

BrightnessBrightness

Depends on the star’s temperature Depends on the star’s temperature and distance from earthand distance from earth

Sirius – brightest star in the night skySirius – brightest star in the night sky

Star ColorStar Color

Related to its temperatureRelated to its temperature Hotter objects glow brighter and have shorter Hotter objects glow brighter and have shorter

wavelengthswavelengths (closer to blue)(closer to blue)

Cooler objects have less intense color and have Cooler objects have less intense color and have longer wavelengthslonger wavelengths

(closer to reds)(closer to reds) The sun appears yellow because the peak The sun appears yellow because the peak

wavelength of the sun is near the color wavelength of the sun is near the color yellow …Yellow also corresponds to a yellow …Yellow also corresponds to a temperature near 6000 kelvintemperature near 6000 kelvin

The Life Cycle of a StarThe Life Cycle of a Star

Stars appear different when they are in Stars appear different when they are in different stages of the life cycledifferent stages of the life cycle

Stars are born, they develop, and they Stars are born, they develop, and they diedie

Stars are “born” from a NEBULA (cloud Stars are “born” from a NEBULA (cloud of gas and dust)of gas and dust)

The SUN is thought to be in middle age The SUN is thought to be in middle age and has about 5 BILLION years left in it.and has about 5 BILLION years left in it.

Star Life CycleStar Life Cycle

Low Mass/Medium Low Mass/Medium Mass StarMass Star

1.1. NebulaNebula

2.2. ProtostarProtostar

3.3. StarStar

4.4. Red GiantRed Giant

5.5. Planetary NebulaPlanetary Nebula

6.6. White dwarfWhite dwarf

7.7. Black dwarfBlack dwarf

High Mass StarHigh Mass Star

1.1. NebulaNebula

2.2. ProtostarProtostar

3.3. StarStar

4.4. Super GiantSuper Giant

5.5. Super NovaSuper Nova

6.6. Neutron star or Black Neutron star or Black holehole

A Star is BornA Star is Born Stars are formed from Stars are formed from

a Nebula collapsing a Nebula collapsing inward and spinning inward and spinning faster and faster. faster and faster.

The center core The center core increases in increases in temperaturetemperature

Nuclear forces begin Nuclear forces begin the process of fusionthe process of fusion

And the star is turned And the star is turned onon

A Dying StarA Dying Star Fusion begins to slow down, pressure Fusion begins to slow down, pressure

in the core drops and the core will in the core drops and the core will contract…causing core temperature to contract…causing core temperature to rise.rise.

RED GIANT – A large reddish star late RED GIANT – A large reddish star late in its life cyclein its life cycle

WHITE DWARF – a small, hot, dim star WHITE DWARF – a small, hot, dim star that is the leftover center of an old starthat is the leftover center of an old star No longer fuses elementsNo longer fuses elements Most stars in our galaxy end as white Most stars in our galaxy end as white

dwarfsdwarfs

SuperGiant StarsSuperGiant Stars

Massive stars that evolve faster than Massive stars that evolve faster than smaller starssmaller stars

Develop hotter cores…create heavier Develop hotter cores…create heavier elements through fusionelements through fusion

Fuses Iron atoms right before its Fuses Iron atoms right before its deathdeath

When fusion stops, the core collapses When fusion stops, the core collapses and causes a shock wave … and and causes a shock wave … and causes a bright explosion.causes a bright explosion.

SuperNovaSuperNova

A gigantic explosion A gigantic explosion from the collapsing from the collapsing of a massive starof a massive star

Supernova Supernova explosions cause explosions cause NEUTRON STARS or NEUTRON STARS or BLACK HOLESBLACK HOLES

Neutron StarNeutron Star

Black HoleBlack Hole An object so massive and dense that not An object so massive and dense that not

even light can escape its gravityeven light can escape its gravity Since no light can escape a black hole Since no light can escape a black hole

cannot be seen directlycannot be seen directly They have a very strong gravitational pull.They have a very strong gravitational pull.

Hertzsprung-Russell DiagramHertzsprung-Russell Diagram P. 673 shows an exampleP. 673 shows an example Helps astronomers understand how stars change Helps astronomers understand how stars change

over timeover time Vertical axis indicates brightnessVertical axis indicates brightness Horizontal axis indicates surface temperature of Horizontal axis indicates surface temperature of

the starthe star When stars are born, they appear as protostarsWhen stars are born, they appear as protostars Position of a star changes as they go through Position of a star changes as they go through

their life cycletheir life cycle Red giants are cool and bright so they are in the Red giants are cool and bright so they are in the

upper rightupper right White dwarfs are faint and hot so they are in the White dwarfs are faint and hot so they are in the

lower left.lower left.