© 2005 pearson education inc., publishing as addison-wesley the sun, our star & the origin of...
Post on 19-Dec-2015
214 views
TRANSCRIPT
© 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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
HHeOCFe
Composition of the Sun(by Mass)
70%28%
0.2%0.3%
C, N, O, Fe: 1%
Hydrogen
He
Magnesium Sodium
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Layers of the Sun
Core RadiationZone
ConvectiveZone
photosphere Corona
SolarWind
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Photon Transport of Energy“Radiation Transport”
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Layers of the Sun
Core RadiationZone
ConvectiveZone
photosphere Corona
SolarWind
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Convective Transport of Energy
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
Wait 10 secFor flame
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Convection Visible atSurface of the Sun
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Layers of the Sun
Core RadiationZone
ConvectiveZone
photosphere Corona
SolarWind
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Photosphere• T = 5,800 K; depth = 400 km
• This is the yellow “surface” that we see.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
The Photosphere:Visible Surface of the Sun
• Photosphere:
opaque “surface”
human eye sees.• Granulation
(convection)• Sunspots
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Sunspots and Convection atSurface of the Sun
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Layers of the Sun
Core RadiationZone
ConvectiveZone
photosphere Corona
SolarWind
Chromosphere
© 2005 Pearson Education Inc., publishing as Addison-Wesley
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Solar Chromosphere
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Chromosphere
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Temp = 10,000 KHydrogen Emission n = 3 to 2.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
Prominences from the Chromosphere
Hydrogen Alpha:Electrons drop from3rd - 2nd level.
Wait 10 secFor movie.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Solar Prominences: Magnetic Ejections
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Solar Flares: Magnetic Explosions
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Solar Flares: Magnetic Explosions
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
The Corona
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Corona
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Coronal Mass Ejections
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Solar Wind
electrons, protons, He nuclei expelled by flares
Interact with Earth’s magnetic field to cause…
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Sunspots: Cool, Magnetic RegionsUmbra, Penumbra
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
What causes a sunspot?
Magnetic field slows down convection;Less heat is transported to surface; so that part of photosphere is cooler
© 2005 Pearson Education Inc., publishing as Addison-Wesley
11-year Sunspot Cycle
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Magnetic Activity changes with Time :11-year Cycle (Last Maximum in Year 2000)
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Magnetic Fields:Winding up, tangling in 11 years
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Rotation Period of Sun: 30 days
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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”
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Fusion of 3 helium nuclei into Carbon
“Triple-Alpha “
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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”.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Planetary Nebulae
Cat’s Eye Nebula
Twin Jet Nebula
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Planetary Nebulae
Ring Nebula Hourglass Nebula
The collapsing Carbon core becomes a White Dwarf
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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 .
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Supernovae
Veil Nebula Tycho’s Supernova (X-rays)exploded in 1572
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
• 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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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.)
© 2005 Pearson Education Inc., publishing as Addison-Wesley
Quarks and Photons Annihilate:Equilibrium
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
t < 0.001 sec
• Quarks and Electrons as numerous as photons.
• T > 0.001 sec:
Quarks combined to form protons & neutrons
© 2005 Pearson Education Inc., publishing as Addison-Wesley
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
Protons and NeutronsAre Composed of 3 Quarks
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
The Universe since the Big Bang: Gravitational Attraction of material
Billions of years ago
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
• 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.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
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
© 2005 Pearson Education Inc., publishing as Addison-Wesley
“Standard” Candles
Bright = near dim = far
dust
dim & red=closer!
Hubble’s Diagram