stars chap. 30 the sun 30.1 measuring stars 30.2 stellar evolution 30.3

StarsStarsChap. 30Chap. 30Chap. 30Chap. 30

The Sun 30.1

Measuring Stars 30.2

Stellar Evolution 30.3

The Sun 30.1The Sun 30.1

ObjectivesObjectives• explore the structure of the Sun• describe the solar activity cycle and how the Sun affects the Earth• compare the different types of spectra

I.I. How do we learn about it?How do we learn about it?

I.I. How do we learn about it?How do we learn about it?A.A. Using solar observatoriesUsing solar observatories

http://hesperia.gsfc.nasa.gov

Dunn Solar Telescope Dunn Solar Telescope Sacramento Peak, NMSacramento Peak, NM

I.I. How do we learn about it?How do we learn about it?

Solar Heliospheric Solar Heliospheric Observatory Observatory (SOHO)(SOHO)

A.A. Using solar observatoriesUsing solar observatories

B.B. Using satellitesUsing satellites

http://sohowww.nascom.nasa.gov/

II.II. PropertiesProperties

II.II. PropertiesPropertiesA.A. The Sun has a very large radiusThe Sun has a very large radius

RadiusRadius

Sun: 695,000 kmSun: 695,000 km

Earth: 6,400 kmEarth: 6,400 km


B.B. The Sun is very massiveThe Sun is very massive

MassMass

Sun: 2.0 Sun: 2.0 xx 10 103030 kg kg

Earth: 6.0 Earth: 6.0 xx 10 102424 kg kg



C.C. The density is similar to that of The density is similar to that of the gas giant planets.the gas giant planets.




1.1. Outer portion is not very denseOuter portion is not very dense




1.1. Outer portion is not very denseOuter portion is not very dense

2.2. Inner portion is much denserInner portion is much denser




D.D. Physical state of matter: Physical state of matter: ..




D.D. Physical state of matter: Physical state of matter: plasmaplasma..

III.III. Layers of AtmosphereLayers of Atmosphere

III.III. Layers of AtmosphereLayers of AtmosphereA.A. PhotospherePhotosphere


1.1. Lowest layerLowest layer

2.2. Only about 400 km thickOnly about 400 km thick

3.3. Average temp: 5800 KAverage temp: 5800 K

4.4. Emits light we can seeEmits light we can see


B.B. ChromosphereChromosphere



1.1. Thicker layer (about 2500 km)Thicker layer (about 2500 km)

2.2. Hotter (average temp: 30,000 K)Hotter (average temp: 30,000 K)

3.3. Difficult to see, except during Difficult to see, except during eclipseeclipse



C.C. CoronaCorona



C.C. CoronaCorona

1.1. Outermost layerOutermost layer

2.2. Extends several million kmExtends several million km

3.3. Very hot (1 to 2 million K)Very hot (1 to 2 million K)

IV.IV. Solar ActivitySolar Activity

Caused when sun’s magnetic field interrupts its Caused when sun’s magnetic field interrupts its atmosphereatmosphere

IV.IV. Solar ActivitySolar ActivityA.A. Solar WindSolar Wind


1.1. Charged particles from sun Charged particles from sun traveling at high speeds (400 km/s)traveling at high speeds (400 km/s)



2.2. Deflected by our magnetic fieldDeflected by our magnetic field



2.2. Deflected by our magnetic fieldDeflected by our magnetic field

3.3. Causes aurorasCauses auroras

http://www.castlegate.net/


B.B. Sun SpotsSun Spots

http://www.galacticimages.com/http://www.galacticimages.com/


B.B. Sun SpotsSun Spots1.1. Appear on photosphereAppear on photosphere



2.2. Look dark because they are coolerLook dark because they are cooler



2.2. Look dark because they are coolerLook dark because they are cooler

3.3. Associated with solar windAssociated with solar wind



C.C. Solar FlaresSolar Flares



C.C. Solar FlaresSolar Flares1.1. Violent eruptions from surfaceViolent eruptions from surface




2.2. Occur in coronaOccur in corona




2.2. Occur in coronaOccur in corona

3.3. Some the size of EarthSome the size of Earth

IV.IV. Solar ActivitySolar ActivityD.D. Solar ProminenceSolar Prominence


1.1. Less violent than flaresLess violent than flares



2.2. Cool sheets of gas that condense Cool sheets of gas that condense from coronafrom corona

IV.IV. Solar ActivitySolar Activity


2.2. Cool sheets of gas that condense Cool sheets of gas that condense from coronafrom corona

3.3. Some rain back material on surfaceSome rain back material on surface

D.D. Solar ProminenceSolar Prominence

V.V. Interior of SunInterior of Sun

V.V. Interior of SunInterior of SunA.A. CoreCore

V.V. Interior of SunInterior of Sun

1.1. Site of fusion (energy production)Site of fusion (energy production)

2.2. Density of 160 g/cmDensity of 160 g/cm33 (15 (15 xx denser denser than lead)than lead)

3.3. Temperature of about 15 million KTemperature of about 15 million K

4.4. Extends 25% to outsideExtends 25% to outside

A.A. CoreCore


B.B. Radiative ZoneRadiative Zone


B.B. Radiative ZoneRadiative Zone1.1. Extends another 60% to outsideExtends another 60% to outside

2.2. Temp. is about 2 million KTemp. is about 2 million K

3.3. Passes energy (photons) from atom Passes energy (photons) from atom to atomto atom



C.C. Convective ZoneConvective Zone



C.C. Convective ZoneConvective Zone1.1. Final 15%Final 15%

2.2. Energy is carried via moving gas Energy is carried via moving gas volumesvolumes

3.3. Temp. is about 5700 KTemp. is about 5700 K

VI.VI. FusionFusion

VI.VI. FusionFusionA.A. Joining of nucleiJoining of nuclei


B.B. Occurs at very high temp./pressureOccurs at very high temp./pressure



C.C. Opposite of fissionOpposite of fission




D.D. Mass is lost during processMass is lost during process

E = mcE = mc22




D.D. Mass is lost during processMass is lost during process

E.E. Tremendous amount of energy Tremendous amount of energy producedproduced

1354 J/m1354 J/m22

VII.VII. Three types of SpectraThree types of Spectra

VII.VII. Three types of SpectraThree types of SpectraA.A. Continuous spectraContinuous spectra

Shows all the colors with no breaksShows all the colors with no breaks


B.B. Emission spectraEmission spectra

Only certain lines produced (depending on Only certain lines produced (depending on elements presentelements present


B.B. Emission spectraEmission spectra

C.C. Absorption spectraAbsorption spectra

Light passes through a gas and some of it is Light passes through a gas and some of it is absorbed (leaving dark, ‘missing’ sections)absorbed (leaving dark, ‘missing’ sections)

VIII.VIII. Composition of SunComposition of Sun

VIII.VIII. Composition of SunComposition of SunA.A. Hydrogen (70%)Hydrogen (70%)


B.B. Helium (28%)Helium (28%)


B.B. Helium (28%)Helium (28%)

C.C. Trace elementsTrace elements

(O, C, Ne, Fe, N, Si, Mg, S)(O, C, Ne, Fe, N, Si, Mg, S)

The End

Measuring the Stars – 30.2

ObjectivesObjectives• describe star

distribution and distance

• classify the types of stars

• summarize the interrelated properties of stars

I.I. Groups of starsGroups of stars

PleiadesPleiades

I.I. Groups of starsGroups of starsA.A. ConstellationsConstellations

Groups of stars named after animals/mythological creaturesGroups of stars named after animals/mythological creatures


OrionOrion

A.A. ConstellationsConstellations


OrionOrion


BetelgeuseBetelgeuse

RigelRigel


A group of stars that are bound by gravityA group of stars that are bound by gravity


B.B. Star ClustersStar Clusters


Stars are loosely bound by gravityStars are loosely bound by gravity


B.B. Star ClustersStar Clusters1.1. Open clusterOpen cluster

PleiadesPleiades

http://upload.wikimedia.org/wikipedia/commons/4/4e/Pleiades_large.jpg


Tightly bound stars, relatively close togetherTightly bound stars, relatively close together



M13, in HerculesM13, in Hercules

1.1. Open clusterOpen cluster

2.2. Globular clusterGlobular cluster


Two stars that are gravitationally bound.Two stars that are gravitationally bound.



C.C. BinariesBinaries

Algol – a blue dwarfAlgol – a blue dwarf

II.II. Stellar Positions and DistancesStellar Positions and Distances

II.II. Stellar Positions and DistancesStellar Positions and DistancesA.A. Stellar distanceStellar distance


The distance traveled by light in one year.The distance traveled by light in one year.

A.A. Stellar distanceStellar distance

1.1. Light year (ly)Light year (ly)

Calculate this!Calculate this!

Light travels at a speed of Light travels at a speed of 300,000 km/s. How many 300,000 km/s. How many miles is a light year?miles is a light year?

Calculate this!Calculate this!

Proxima Centauri is 4.24 light Proxima Centauri is 4.24 light years. How many kilometers years. How many kilometers is this star?is this star?


The distance of a star when it appears to shift The distance of a star when it appears to shift one second of a degree due to parallax.one second of a degree due to parallax.

1 pc = 3.26 ly.1 pc = 3.26 ly.



2.2. Parsec (pc)Parsec (pc)


The apparent shift in position of an object as The apparent shift in position of an object as the observer’s location changesthe observer’s location changes



2.2. Parsec (pc)Parsec (pc)

3.3. ParallaxParallax

Calculate this!Calculate this!The brightest star in The brightest star in the sky (besides the the sky (besides the Sun) is Sirius. It is Sun) is Sirius. It is 2.6 pc from Earth. 2.6 pc from Earth. How long does it How long does it take light from take light from Sirius to reach us?Sirius to reach us?

II.II. Stellar Positions and DistancesStellar Positions and DistancesB.B. Other Properties of StarsOther Properties of Stars

http://astronote.org


1.1. Apparent MagnitudeApparent Magnitude

How bright a star appears. (affected by How bright a star appears. (affected by luminosity and distance)luminosity and distance)

MagnitudeMagnitudeThe lower the number the brighter The lower the number the brighter the object.the object.

Each value increase equates to Each value increase equates to about 2.512 decrease in brightness.about 2.512 decrease in brightness.

Magnitude of celestial objectsMagnitude of celestial objects



2.2. Absolute MagnitudeAbsolute Magnitude

How bright a star would appear at 10 pc. (How bright a star would appear at 10 pc. (This This

can be calculated if you know the actual distance.)can be calculated if you know the actual distance.)




3.3. LuminosityLuminosity

The energy output from the surface of a star. The energy output from the surface of a star. Can be measured in joules/second or watts.Can be measured in joules/second or watts.





4.4. Spectra of StarsSpectra of Stars

The types (colors) of light given offThe types (colors) of light given off






Cooler stars have more lines in spectra Cooler stars have more lines in spectra

a.a. Determined by temperatureDetermined by temperature






O5, A4, A5, G2 (sun), etc.O5, A4, A5, G2 (sun), etc.

a.a. Determined by temperatureDetermined by temperature

b.b. Given a letter & number rankingGiven a letter & number ranking





4.4. Spectra of StarsSpectra of Starsa.a. Determined by temperatureDetermined by temperature

b.b. Given a letter & number rankingGiven a letter & number ranking

c.c. Light spectra can shift due to Light spectra can shift due to motionmotion






5.5. H-R diagram (Hertzsprung-Russell)H-R diagram (Hertzsprung-Russell)

Used to classify stars based on spectra & magnitudeUsed to classify stars based on spectra & magnitude

The End

Stellar Evolution – 30.3ObjectivesObjectives• Explain how

astronomers learn about the internal structure of stars

• Describe how the Sun will change during its lifetime and how it will end

• Compare the evolutions of stars of different masses

I.I. IntroductionIntroduction

I.I. IntroductionIntroductionA.A. A star is balances two forcesA star is balances two forces


1.1. Inward force: Inward force: .


1.1. Inward force: Inward force: gravitygravity

2.2. Outward force: _________________Outward force: _________________


1.1. Inward force: Inward force: gravitygravity

2.2. Outward force: Outward force: fusion and radiationfusion and radiation

I.I. IntroductionIntroductionB.B. Structure of a star depends on:Structure of a star depends on:


Elements a star is made ofElements a star is made of

1.1. CompositionComposition

B.B. Structure of a star depends on:Structure of a star depends on:


The total amount of material in a starThe total amount of material in a star


2.2. MassMass



Pull inward which is balanced by force outwardPull inward which is balanced by force outward


2.2. MassMass

GravityGravity



Higher temperature counter higher gravity.Higher temperature counter higher gravity.


2.2. MassMass

GravityGravity

TemperatureTemperature



When temperatures increase so do reaction rates.When temperatures increase so do reaction rates.


2.2. MassMass

GravityGravity

TemperatureTemperature Rate of FusionRate of Fusion



Star produces more energy, and is brighter.Star produces more energy, and is brighter.


2.2. MassMass

GravityGravity

TemperatureTemperature Rate of FusionRate of Fusion

LuminosityLuminosity


II.II. FusionFusion

Energy producing reaction in starsEnergy producing reaction in stars

II.II. FusionFusion

Most stars fall in this categoryMost stars fall in this category

A.A. Main sequence Main sequence starsstars

II.II. FusionFusion

1.1. Start by fusing H + H to HeStart by fusing H + H to He

A.A. Main sequence starsMain sequence stars

II.II. FusionFusion


2.2. He + He + He to CHe + He + He to C


II.II. FusionFusion



3.3. He + C to He + C to oxygenoxygen


II.II. FusionFusion




4.4. He + O to He + O to neonneon


II.II. FusionFusion





5.5. He + Ne to He + Ne to magnesiummagnesium


II.II. FusionFusion





5.5. He + Ne to He + Ne to magnesiummagnesium

6.6. This stops at iron because fusion of This stops at iron because fusion of larger elements is no longer larger elements is no longer favorable.favorable.


III.III. Life cycle of SunLife cycle of Sun

III.III. Life cycle of SunLife cycle of SunA.A. Star formationStar formation


1.1. Nebula collapses on itself from its Nebula collapses on itself from its own gravityown gravity

A.A. Star formationStar formation

Nebula is an interstellar cloud of gas and dustNebula is an interstellar cloud of gas and dust

Orion NebulaOrion Nebula


1.1. Nebula collapses on itself from its Nebula collapses on itself from its own gravityown gravity

2.2. Protostar forms in center of disk Protostar forms in center of disk shape, emitting lots of infrared lightshape, emitting lots of infrared light

A.A. Star formationStar formation

III.III. Life cycle of SunLife cycle of SunB.B. Fusion begins. . .Fusion begins. . .


1.1. when minimum temperature is when minimum temperature is reachedreached



2.2. this often illuminates surrounding this often illuminates surrounding gasesgases

Rosette NebulaRosette Nebula



2.2. this often illuminates surrounding this often illuminates surrounding gasesgases

3.3. star enters main-sequence phase – star enters main-sequence phase – primarily converting H to He.primarily converting H to He.

True or False?True or False?

Large main-sequence stars last Large main-sequence stars last longer than smaller main-sequence longer than smaller main-sequence stars.stars.

True or False?True or False?

Large main-sequence stars last Large main-sequence stars last longer than smaller main-sequence longer than smaller main-sequence stars.stars.

FalseFalse – larger stars get hotter, and use – larger stars get hotter, and use their fuel up faster.their fuel up faster.

III.III. Life cycle of SunLife cycle of SunC.C. Becoming a Red GiantBecoming a Red Giant

A larger, cooler star that is very luminous.A larger, cooler star that is very luminous.

BetelgeuseBetelgeuse


1.1. After about 10 billion years, hydrogen After about 10 billion years, hydrogen is used upis used up



2.2. Core of star is made of HeCore of star is made of He




3.3. Layer of gas surrounding core does Layer of gas surrounding core does fusion, causing gases to expand and fusion, causing gases to expand and coolcool





4.4. Outer layers are driven away due to Outer layers are driven away due to decrease in surface gravitydecrease in surface gravity





4.4. Outer layers are driven away due to Outer layers are driven away due to decrease in surface gravitydecrease in surface gravity

5.5. He in core reacts to form CHe in core reacts to form C

III.III. Life cycle of SunLife cycle of SunD.D. Becoming a White DwarfBecoming a White Dwarf


1.1. Star is not big enough to further react Star is not big enough to further react carboncarbon



2.2. Gases surrounding star expend and Gases surrounding star expend and are driven offare driven off




3.3. Core remains as small, hot, earth-Core remains as small, hot, earth-sized objectsized object




3.3. Core remains as small, hot, earth-Core remains as small, hot, earth-sized objectsized object

4.4. This star is made of carbonThis star is made of carbon

IV.IV. Massive StarsMassive Stars

MonocerotisMonocerotis

IV.IV. Massive StarsMassive StarsA.A. Same beginning – but hydrogen Same beginning – but hydrogen

fusion happens quicklyfusion happens quickly



B.B. Star expands and contracts to Star expands and contracts to repeatedly, forming variety of repeatedly, forming variety of elements (not bigger than Fe)elements (not bigger than Fe)



B.B. Star expands and contracts to Star expands and contracts to repeatedly, forming variety of repeatedly, forming variety of elements (not bigger than Fe)elements (not bigger than Fe)

C.C. Mass if lost by stellar windMass if lost by stellar wind

IV.IV. Massive StarsMassive StarsD.D. Size determines fateSize determines fate


1.1. If star’s mass is If star’s mass is < 1.4 x Sun’s size< 1.4 x Sun’s size it it becomes a white dwarf.becomes a white dwarf.



2.2. If star’s mass is > 1.4 x Sun’s size it’s If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging gravity pulls gases inward, merging protons and electrons in protons and electrons in ..



2.2. If star’s mass is > 1.4 x Sun’s size it’s If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging gravity pulls gases inward, merging protons and electrons in protons and electrons in neutronsneutrons..



2.2. If star’s mass is > 1.4 x Sun’s size it’s If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging gravity pulls gases inward, merging protons and electrons in protons and electrons in neutronsneutrons..a.a. These are neutron starsThese are neutron stars




b.b. They are very dense – 3x Sun’s They are very dense – 3x Sun’s mass squeezed into 10 km radius.mass squeezed into 10 km radius.




b.b. They are very dense – 3x Sun’s They are very dense – 3x Sun’s mass squeezed into 10 km radius.mass squeezed into 10 km radius.

c.c. Particles from outer layer bounce Particles from outer layer bounce off neutron star creating supernovaoff neutron star creating supernova



2.2. If star’s mass is > 1.4 x Sun’s size it’s If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging gravity pulls gases inward, merging protons and electrons in protons and electrons in neutronsneutrons..

3.3. If star’s mass is 3 x Sun’s size it If star’s mass is 3 x Sun’s size it becomes a black hole.becomes a black hole.

The End

stars chap. 30 the sun 30.1 measuring stars 30.2 stellar evolution 30.3

Documents

solar wind slide

photosphere slide

chromosphere slide

kms slide

corona slide

dense slide

solar wind b

nm slide