© 2005 Pearson Education Inc., publishing as Addison-Wesley The Sun, Our Star & The Origin of Atoms...

© 2005 Pearson Education Inc., publishing as Addison-Wesley

The Sun, Our StarThe Sun, Our Star&&

The Origin of AtomsThe Origin of Atoms

Solar Telescope Outside Class:

Light filter used: Hydrogen emission passes to camera. Reveals Chromosphere.


Announcements

• Telescope open tonight at Telescope open tonight at 8:30pm : last night !8:30pm : last night !

• Homework due Friday on Homework due Friday on

Extrasolar planets (Chap. 13)Extrasolar planets (Chap. 13)• Both Observation ReportsBoth Observation Reports

also due Friday. also due Friday.


HHeOCFe

Composition of the Sun(by Mass)

70%28%

0.2%0.3%

C, N, O, Fe: 1%

Hydrogen

He

Magnesium Sodium


Layers of the Sun

Core RadiationZone

ConvectiveZone

photosphere Corona

SolarWind


Photon Transport of Energy“Radiation Transport”

QuickTime™ and aDV/DVCPRO - NTSC decompressor

are needed to see this picture.


Energy Transport by Photons (Light)• Radiation Zone

• Energy travels as photons of light, which continually collide with particles

• Photons scatter, changing direction (random walk), and change wavelengths

• This is called radiative diffusion

• This is a slow process!

• It takes about 1 million years for energy to travel from the core to the surface.

Path of photon,scattered by electronsand atoms.


Layers of the Sun

Core RadiationZone

ConvectiveZone

photosphere Corona

SolarWind


Convective Transport of Energy



Wait 10 secFor flame


Convective Energy Transport

• Convection: Hot air rises; carries heat with it.• The bottom of the convection zone is heated … hot gas rises to the top

• cooler gas sinks to the bottom…similar to boiling a pot of water!

• Energy is brought to the surface via bulk motions of matter


Convection Visible atSurface of the Sun

QuickTime™ and aYUV420 codec decompressor



Layers of the Sun

Core RadiationZone

ConvectiveZone

photosphere Corona

SolarWind


Photosphere• T = 5,800 K; depth = 400 km

• This is the yellow “surface” that we see.


The Photosphere:Visible Surface of the Sun

• Photosphere:

opaque “surface”

human eye sees.• Granulation

(convection)• Sunspots




Journey Into the Sun

• Photosphere• Convection Zone• Radiation Zone• Core: proton-proton

nuclear reactions: Helium

QuickTime™ and aSorenson Video decompressorare needed to see this picture.


Photospheric Features

Granulation: the tops of convection cells seen “bubbling” on the Solar surface

Sunspots: dark spots on the surface where the temperature is cooler.

National Solar Observatory/AURA/NSFNational Solar Observatory/AURA/NSF


Sunspots and Convection atSurface of the Sun




Layers of the Sun

Core RadiationZone

ConvectiveZone

photosphere Corona

SolarWind

Chromosphere


QuickTime™ and aTIFF (Uncompressed) decompressor


Solar Chromosphere


Chromosphere



Temp = 10,000 KHydrogen Emission n = 3 to 2.


Chromosphere• T = 10,000 K; • Depth: Thin and patchy over surface• A thin hot layer above the photosphere where most of the Sun’s UV light is emitted.

SOHO

• UV image of the Sun Light emitted from

Helium at 20,000 K




Prominences from the Chromosphere

Hydrogen Alpha:Electrons drop from3rd - 2nd level.

Wait 10 secFor movie.


Prominences – Gas trapped in the magnetic fields is heated and elevated above the photosphere and chromosphere.

X-ray images from NASA’s TRACE mission.Movie. Click to launch.


Solar Prominences: Magnetic Ejections




Solar Flares: Magnetic Explosions






The Corona


Corona




Corona• T = 2 Million K• Thickness Radius of Sun (700,000 km)• The hot, ionized gas which surrounds the Sun.

– it emits mostly X-rays

• It can be seen in visible light during an eclipse.

X-ray image (YOHKOH telescope)Visible image


Coronal Mass Ejections




Solar Wind• The stream of electrons, protons, Helium nuclei and

other ions which flow out from the Sun.• It extends out beyond Pluto.

X-ray image of corona

UV image of solar wind

Visible image of solar wind

comet SOHO-6 (fell into Sun)

Sagittarius


Solar Wind

electrons, protons, He nuclei expelled by flares

Interact with Earth’s magnetic field to cause…


The Aurorae

• A strong Solar wind can affect human technology by:• interfering with

communications

• knocking out power grids

• damage electronics in space vehicles

the Northern & Southern Lights


Solar Magnetic Activity

• The photosphere of the Sun is covered with sunspots.• Sunspots are not constant; they appear & disappear.• They do so in a cycle, lasting 11 years.

• Sun’s magnetic field switches polarity (N-S) every 11 yrs

• So the entire cycle repeats every 22 yrs


Sunspots: Cool, Magnetic RegionsUmbra, Penumbra




What causes a sunspot?

Magnetic field slows down convection;Less heat is transported to surface; so that part of photosphere is cooler


11-year Sunspot Cycle




Magnetic Activity changes with Time :11-year Cycle (Last Maximum in Year 2000)




Sunspot Cycle


Magnetic Fields:Winding up, tangling in 11 years




Rotation Period of Sun: 30 days




The Sun:The Sun:How long will it Shine ?How long will it Shine ?

Until it burns up its available Hydrogen(in the core where T > 2 million degrees)

At Current Rate of Energy production:

5 billion more years


The Death of the Sunin 5 Billion Years

• Core becomes pure helium! No Hydrogen burning possible.• The Helium core begins to collapse.

– H shell (around Helium) heats up and H fusion begins there.– Outer layers of the Sun expand.– The Sun enters giant phase of its life.

Original Sun Expanding:“Giant Star”


Giant Star Phase• The He core collapses until it heats to 108 K

– He fusion begins ( 3 He C) Carbon forms!

• The star, called a Giant, is once again stable.– Gravity balanced by pressure, from He fusion reactions– Giant stars create, and release, most of the Carbon in the

universe: Key ingredient for organic molecules and life.

The Dying Sun: 5 billions years from now


Fusion of 3 helium nuclei into Carbon

“Triple-Alpha “




Planetary Nebula

• When the Giant star exhausts its Helium fuel in the central core:

– the Carbon core collapses.

– Low & solar-mass starsLow & solar-mass stars don’t have enough gravitational energy to heat to 6 x 108 K (temperature where Carbon fuses)

• The He & H burning shells produce huge amounts of energy.

• The energy blows away the star’s outer layers of gas:

• Making a “planetary nebula”.


Planetary Nebulae

Cat’s Eye Nebula

Twin Jet Nebula


Planetary Nebulae

Ring Nebula Hourglass Nebula

The collapsing Carbon core becomes a White Dwarf


When High Mass Stars Die:Supergiants

• They Contract, heat up to 600 million K. – C fuses into O.

• C is exhausted, core collapses until O fuses.

• The cycle repeats itself.– O burns to Ne.– Ne burns to Mg.– Mg burns to Si.– Si burns to Fe.

They exhaust H fuel.He C .


Supernova

• The mass of the iron (Fe) core increases

- No nuclear reactions: no energy production!– Gravity overwhelms the gas pressure

– Electrons are smashed into protons neutrons

• The neutron core collapses until abruptly stopped by neutrinos flying outward!– this takes only seconds

– The core recoils, bounces, and neutrinos force the gas outward in an explosion.


Supernova Explosions

Crab Nebula in Taurussupernova exploded in 1054

The explosion brings temperature toBillions of degrees:

The elements heavier than Fe are instantly created

Four supernovae have been observed in our part of the Milky Way Galaxy: 1006, 1054, 1572, & 1604


Supernovae

Veil Nebula Tycho’s Supernova (X-rays)exploded in 1572


Where did all the Hydrogen and Helium

Come from?

The 92 atomic elements were all constructed in the centers of stars

(except hydrogen, helium and lithium).

The Origin of the Atomic Elements

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.


• Explosion: Hot and Dense. Over a trillion degrees.• Universe expands ever since. Accelerating now.• Science can not describe what happened before the Big Bang.

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

• Time and Space Created.

• 13.5 Billion Years Ago.


t < 0.001 sec

• Quarks and Electrons as numerous as photons.

(No Protons or neutrons: At billions of degrees,any protons collide, break apart into quarks.)


Quarks and Photons Annihilate:Equilibrium




t < 0.001 sec

• Quarks and Electrons as numerous as photons.

• T > 0.001 sec:

Quarks combined to form protons & neutrons




Protons and NeutronsAre Composed of 3 Quarks


Era of Nucleosynthesis (t < 3 min)

• Protons & neutrons fuse ! 4p He• Some He nuclei torn apart by the high temperatures

• When Universe was 3 min old, it had cooled to 109 K.• At this point, the fusion stopped

• Afterwards, the matter in the Universe was:• 75% Hydrogen nuclei (i.e. individual protons)

• 25% Helium nuclei

• trace amounts of Deuterium (H isotope) & Lithium nuclei




The Universe since the Big Bang: Gravitational Attraction of material

Billions of years ago


Era of Galaxies ( t > 109 yr)

• The first galaxies came into existence about 1 billion years after the Big Bang.

• This is the current era of the Universe.


• Hot and Dense : Over a trillion degrees.• Science can not describe what happened before the Big Bang.

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

• Time and Space Created.

• 13 Billion Years Ago.


Luminosity “Standard Candles”Marking Distance in the Universe

• Giant Stars spilling mass onto white dwarfs• White dwarfs explode when Mass > 1.40 MSUN

White Dwarf

An explosion resulting from the thermonuclear detonation of a White Dwarf Star

Type Ia Supernova


The life of a Supernova Ia Age:Age: -6 days

Maximum

+26 days

+47 days

+102 days

5110

On the Rise for 6 days

2/1tDecline for 79 days


“Standard” Candles

Bright = near dim = far

dust

dim & red=closer!

Hubble’s Diagram


The Dim, the Distant

and the Dusty

Improved SN Ia distancesreveal motion of Local Group,constrains < 0.5 from flows

Riess et al 1995,1997

© 2005 Pearson Education Inc., publishing as Addison-Wesley The Sun, Our Star & The Origin of Atoms...

Documents

Transcript of © 2005 Pearson Education Inc., publishing as Addison-Wesley The Sun, Our Star & The Origin of Atoms...