© 2005 Pearson Education Inc., publishing as Addison-Wesley The Sun, Our Star & The 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 8:30pm : last night !Telescope open tonight at 8:30pm : last night ! Homework due Friday onHomework 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 Composition of the Sun (by Mass) 70% 28% 0.2% 0.3% C, N, O, Fe: 1% Hydrogen He MagnesiumSodium

© 2005 Pearson Education Inc., publishing as Addison-Wesley Layers of the Sun Core Radiation Zone Convective Zone photosphere Corona Solar Wind

© 2005 Pearson Education Inc., publishing as Addison-Wesley Photon Transport of Energy “Radiation Transport”

© 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 electrons and atoms.

© 2005 Pearson Education Inc., publishing as Addison-Wesley Layers of the Sun Core Radiation Zone Convective Zone photosphere Corona Solar Wind

© 2005 Pearson Education Inc., publishing as Addison-Wesley Convective Transport of Energy Wait 10 sec For 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 at Surface of the Sun

© 2005 Pearson Education Inc., publishing as Addison-Wesley Layers of the Sun Core Radiation Zone Convective Zone photosphere Corona Solar Wind

© 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

© 2005 Pearson Education Inc., publishing as Addison-Wesley Journey Into the Sun Photosphere Convection Zone Radiation Zone Core: proton-proton nuclear reactions: Helium

© 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/NSF

© 2005 Pearson Education Inc., publishing as Addison-Wesley Sunspots and Convection at Surface of the Sun

© 2005 Pearson Education Inc., publishing as Addison-Wesley Layers of the Sun Core Radiation Zone Convective Zone photosphere Corona Solar Wind Chromosphere

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

© 2005 Pearson Education Inc., publishing as Addison-Wesley Chromosphere Temp = 10,000 K Hydrogen 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 Prominences from the Chromosphere Hydrogen Alpha: Electrons drop from 3rd - 2nd level. Wait 10 sec For 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

© 2005 Pearson Education Inc., publishing as Addison-Wesley Solar Flares: Magnetic Explosions

© 2005 Pearson Education Inc., publishing as Addison-Wesley Solar Flares: Magnetic Explosions

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

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

© 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

© 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 Regions Umbra, Penumbra

© 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

© 2005 Pearson Education Inc., publishing as Addison-Wesley Magnetic Activity changes with Time : 11-year Cycle (Last Maximum in Year 2000)

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

© 2005 Pearson Education Inc., publishing as Addison-Wesley Magnetic Fields: Winding up, tangling in 11 years

© 2005 Pearson Education Inc., publishing as Addison-Wesley Rotation Period of Sun: 30 days

© 2005 Pearson Education Inc., publishing as Addison-Wesley The Sun: 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 Sun in 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 10 8 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 “

© 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 stars –Low & solar-mass stars don’t have enough gravitational energy to heat to 6 x 10 8 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 Taurus supernova exploded in 1054 The explosion brings temperature to Billions 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

© 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. Time and Space Created Billion Years Ago.

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

© 2005 Pearson Education Inc., publishing as Addison-Wesley t < sec Quarks and Electrons as numerous as photons. T > sec: Quarks combined to form protons & neutrons

© 2005 Pearson Education Inc., publishing as Addison-Wesley Protons and Neutrons Are 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 10 9 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

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 > 10 9 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. Time and Space Created. 13 Billion Years Ago.

© 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 M SUN 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: -6 days Maximum +26 days +47 days +102 days On the Rise for 6 days Decline for 79 days

© 2005 Pearson Education Inc., publishing as Addison-Wesley “Standard” Candles Bright = near dim = far dust dim & red=closer! Hubble’s Diagram

© 2005 Pearson Education Inc., publishing as Addison-Wesley The Dim, the Distant and the Dusty Improved SN Ia distances reveal motion of Local Group, constrains < 0.5 from flows Riess et al 1995,1997