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ASTR 1020 General Astronomy: Stars and Galaxies REVIEW Newton’s Laws • Law #1: A body at rest or in motion remains that way unless acted upon by an outside force. • Law #2: a=F/m • Law #3: For every action there is an equal and opposite reaction. Newton’s Law of Universal Gravitation Gm1m2 F21 = r2 Gm1m2 F12 = r2 (Law #3 Satisfied) G = 6.7x10-8 dyne.cm2/g2 in cgs units Value of G is measured. Nobody knows why it is the value it is. Electrical Force Equation Similar e1e2 Fe = 2 r Example Calculate the period of a planet that is the same distance from the star Sirius that the Earth is from the Sun. r=1.5x1013cm G=6.7x10-8 M=4x1033g (1.5 x1013 ) 3 4 x1039 13 12 6 7 P = 6.28 = 6 . 3 = 6 . 3 1 . 5 x 10 = 6 . 3 x 15 x 10 = 25 x 10 = 2 . 5 x 10 s 33 26 −8 6.7 x10 x 4 x10 2.5 x10 About 9 Months Escape Velocity R Fall from Large Height 1 2 GMm mv = 2 R Same Energy Needed to Reverse and Fly Away 2GM ve = R Escape velocity is the speed at which object must be thrown upward to escape and never come down. Surface Gravity Force of Gravity at Surface of Body is So GMm ma = R2 or GM a= 2 R F= GMm R2 The acceleration of a body near the surface. Independent of mass. Remember Galileo and the Leaning Tower of Pisa Formation of the Solar System Universe is about 12 Billion Years old (3x1017s) Milky Way 10 Billion Years old Sun and Planets – 4.6 Billion Years old Sun has done about 25 orbits of Milky Way Stars are being formed all the time -- some young, some old Stars are formed from clouds of gas A Star Is Held Up By Thermal Pressure From Below Gravity Outer Mass Individual Atoms Don’t Orbit Entire Inside of Star Like This They Jostle Each Other But Effect Is The Same Temperature Scales • Fahrenheit – – 0=salt water freeze 100=human body • Celsius – – 0=pure water freeze 100=water boil (sea level) C=(F-32)x5/9 • Kelvin – – – 0=absolute zero 100 degrees between freeze and boil K=C+273 -273C = 0K = Absolute Zero At Absolute Zero Atoms Stop Moving The Nuclear Core Envelope 1 Million K core 15x106K Photosphere 5000K At Surface Cosmic Composition • • • • • H He O C N hydrogen helium oxygen carbon nitrogen 89% by number 11% 0.1% 0.06% 0.015% Pretty much the composition of the entire universe. Sun and Jupiter have this composition Earth does not. Proton-Proton Chain Bottom Line: H+H+H+H → He 1 1 1H +1H → 1H2 + e+ + ν 2 1 1H +1H 3 3 2He +2He → 2He3 + γ → 2He4 + 1H1 + 1H1 5x106 < T < 2x107K CNO Cycle 12 1 6C +1H 13 7N → 6C13 + e+ + ν 13 1 6C +1H 14 1 7N +1H 15 8O → 7N13 + γ → 7N14 + γ → 8O15 + γ → 7N15 + e+ + ν 15 1 7N +1H 2x107 < T < 108K → 6C12 + 2He4 Net: 1H1 +1H1 + 1H1 +1H1 → 2He4 + 2e+ + 4γ +2ν hydrogen -> helium + energy Triple-α Reaction 4 4 2He +2He ⇔ 4Be8 + γ 8 4 4Be +2He → 6C12 + γ T < 108K Must be very dense for this to work Be8 decays back into helium very quickly unless struck by another He4 Net: 2He4 +2He4 + 2He4 +2He4 → 6C12 + 2γ helium -> carbon + energy Too low density in Big Bang Solar Schematic Sunspot Cycle During mid 1600’s sunspots became non-existent Maunder Minimum Solar Wind 5x105K Corona 2x106K Transition Region 105K Chromosphere 104K Photosphere 5500K Star Names • Arabic Names – Antares, Capella, Mira, etc. • Constellations α Orionis, β Cygni, … then 49 Ori, 50 Ori, etc. • Catalogues HD80591, SAO 733421, etc • RA and Dec – just position in the sky Proper Motion 2003 All stars move Nearby stars move faster Appear to move against fixed field 1900 Can Take Many Years Use Old Photographic Plates Parallax I year cycle The Parsec 1 parsec 1AU 1 arcsecond 360 degrees in circle 60 arcminutes per degree 60 arcseconds per arcminute 200,000AU = 1 parsec = 3x1018cm parsec ---- parallax second The Magnitude System Ptolemy Broke Stars into 5 magnitude groups m=1 the brightest, m=5 the faintest In 1700’s it was found this was a logarithmic scale, as that is how the naked eye responds. Also, faintest were about 100x fainter than brightest. Break the factor of 100 into 5 equal factors: Start with Vega Polaris 2.51x fainter 2.5x fainter than Polaris 2.5x fainter than that etc m=1 m=2 m=3 m=4 1mag = 5 100 = 2.51 Absolute Magnitude The magnitude a star would have were it at 10pc We see a star of magnitude m=10 at 100 pc. What would be its magnitude (M) if it were at 10 pc instead of 100pc? At 10 times closer the star would be 100x brighter = 5 magnitudes M = 10-5 = 5 M = m − 5 log10 d + 5 M = 10 − 5 log 100 + 5 = 10 − 10 + 5 = 5 Light Waves λ lambda is lower case Greek L stands for length Each photon is a sine wave moving at the speed of light Wavelength is usually measure in Angstroms 1Å = 10-8cm =10-10m about the diameter of an atom. Electric and Magnetic Fields Sloshing Back And Forth Parts of EM Spectrum Radio Infrared Visible Ultraviolet X-ray Gamma-ray λ > 1mm (107A) 1mm> λ > 10000Α 10,000Α > λ > 3500Α 3500Α > λ > 100Α 100A > λ > 0.1A 0.1A > λ Speed of Light Speed of Light c = 3x1010cm/s That’s a very odd statement 2 cars at 65mph 1 car at 130mph Cover same distance in same amount of time The Relative speeds are the same Frequency λ λ λ λ Moves λ during each cycle Frequency is the number of cycles per second, ν Moves distance λ for each of ν cycles each second λν = c Greek “nu” Energy of a Photon ε = hν h = 6.63x10-27 erg s Planck’s Constant ε = 6.6 x10 −27 x6 x1014 = 4 x10 −12 ergs Sunlight is 107 ergs/cm2/s energy of yellow photon Outside we have 1019 photons/cm2/s hit us Spectroscopy Spectrum is plot of number of photons as a function of wavelength Tells us huge amounts about nature of object emitting light. Thermal Radiation Planck’s Law I= 2hc 2 1 λ5 e hc λkT − 1 Temperature Determines Where Spectrum Peaks Position of Peak Determines Color Wien’s Law λ peak 3 x10 = T 7 Å (T in Kelvin) As T rises, λ drops Bluer with temperature 300K 5500 106 100,000A 5500 30 Earth Sun X-ray source Stefan-Boltzman Law L = σAT 4 σ = 5.67x10-5 A is area in cm2 T in Kelvins Example: The Sun L = 5.7x10-5 x 4 x 3.14 x (7x1010cm)2 x (5500K)4 = 4 x 1033 ergs 4x1033ergs = 4x1026 Watts = 100 billion billion MegaWatts!! Emission Lines Electron Drops Energy Levels of H Photon Escapes Can Only Happen Between Certain Pre-determined orbitals Each Element Has Different Orbitals So Each Element Has Different Lines Spectrum of Hydrogen Absorption Lines Light moving through cold gas can have photons removed. Creates dark wavelengths called absorption lines Stellar Classification Full range of surface temperatures from 2000 to 40,000K Spectral Classification is Based on Surface Temperature Hottest O B A F G K M { } Kiss Me Oh Be A Fine Girl Guy Each Letter has ten subdivisions from 0 to 9 0 is hottest, 9 is coolest Coolest Stellar Classification (2) Sun α Cen Sirius Antares Rigel G2 G2 + K5 A1 M1 B8 O5 B5 A5 F5 G5 K5 M5 40,000K 15,500 8500 6580 5520 4130 2800 Letters are odd due to confusion in sorting out temperature scale between 1900 and 1920 The Doppler Shift vt ct Observer D During t seconds, source emits n waves of wavelength λ. They move ct during that time. But source also moves vt during that time. So the n waves are scrunched into ct-vt instead of the usual ct Thus the wavelength is reduced from λ to λ ( ct − vt c−v =λ = λ 1− v c ct c ) The Doppler Formula ⎛ ⎝ v⎞ c⎠ λ = λ0 ⎜1 − ⎟ δλ λ0 − λ V = = λ0 λ0 c v is positive if coming toward us Wavelength λ decreases from lab value δν v − v0 V = = ν0 v0 c Frequency shifts up as source approaches The H-R Diagram Plot of Brightness vs Temperature -5 Giants Rigel Capella Brightness 0 Sirius Procyon Sun +5 Main Sequence α Cen B White Dwarfs +10 Sirius B Prox Cen +15 O B A F G Spectral Type K M MS Lifetime What determines amount of time a star stays on Main Sequence? Just like a kerosene heater: Amount of fuel and rate of burn. More Mass = More Fuel More Luminosity = Greater Burn Rate We can scale from the Sun: M = 1M~ L = 1L~ Sun lasts 1010 years M MSLife = 10 L 10 M in solar masses L in solar luminosities Some Lifetimes Sun Sirius Prox Cen Rigel Mass Luminosity Lifetime in Billion Years 1 2 .4 8 1 10 .001 10,000 10 2 4000 .008 Dinky little stars like Prox Cen will last trillions of years Huge stars like Rigel are gone in a few million There aren’t many large stars out there, because they don’t last. 10,000 O stars of the 100,000,000,000 Milky Way stars Chemical Energy for Sun? Chemical Energy Generates 2eV per atom in forming molecule (burning) 2eV = 3x10-19 Joules Number of Atoms in Sun: M 2 x1030 kg N= = = 1057 − 27 m p 1.6 x10 kg Available Energy E = 3 x10 −19 x1057 = 3 x1038 J Time it can run: E 3 x1038 J 11 t= = = 7 x 10 s = 20,000 years 26 L 4 x10 W Gravitational Energy? Available Gravity Energy: Time it can run: ( GM 2 6 x10−11 x 2 x1030 E= = R 7 x108 ) 2 24 x1049 41 = = 3 x 10 J 8 7 x10 E 3 x10 41 15 7 t= = = = 10 s 3 x 10 years 26 L 3 x10 Sun can only run 30million years on gravity. It does this during formation Best understanding of Sun until Einstein. Nuclear Energy for Sun? Nuclear Energy Generates 2MeV per atom in forming molecule (burning) 2MeV = 3x10-13 Joules Number of Atoms in Sun: E = 3 x10 −13 x1057 = 3 x10 44 J Available Energy Time it can run: M 2 x1030 kg N= = = 1057 − 27 m p 1.6 x10 kg E 3 x10 44 J 17 t= = = 7 x 10 s = 20,000,000,000 years 26 L 4 x10 W Sun can run 20 Billion years on nuclear energy Which is what it does. Outer Envelope of Star Expands Force of photon flux from below lifts outer parts of star. Core gets smaller and hotter, but Surface gets larger and cooler. What’s Happening in Core? H H H->He H->He He In the center, H is depleted, but He too cool to burn. “Shell Burning” describes source of nuclear power around dead center Electron Degeneracy •Helium Density Rises •Center of Sun has density of 10g/cc •When density in center of star reaches ~30,000g/cc •a new phenomenon kicks in •Electron Degeneracy •A purely quantum mechanical phenomenon Helium Flash When degenerate He core reaches about 108K, the nuclei can burn by the Triple Alpha Reaction. (He+He+He->C) They start to burn and release energy. Pressure rises and temperature rise, but volume does not increase. P and T rise some more. Finally, P gets so great it lifts the degeneracy and thermal pressure equilibrium is re-established. This is the “He Flash” Could blow a star apart, but it doesn’t. After the Flash H H H->He H->He He->C He->C C Helium Burns in the Center Starts to Development Dead C Core Red Giants Earth Orbit Nucleus Planetary Nebulae Gas blown out into space and illuminated by central star. The star is the degenerate C core. The Ring Nebula Hourglass 2 Next Explosion is Constrained and Expands as Hour-Glass White Dwarfs • • • • Held up by electron degeneracy About the size of the Earth R~5000km Mass Typically 0.8M~ Luminosity ~ .001 L~ Thin layer of “normal” H Degenerate Carbon Some Famous White Dwarfs • Sirius B • 40 Eridani B • Procyon B All in binaries around nearby stars. Establishes the WD is close and small. Earth vs White Dwarf Mass Radius Relation 1 R∝ 3 M As mass increases star gets smaller. Like ball of foam. WD Density 2 x1033 6 ρ= = = 1.5 x10 g / cc 8 3 4 3 4 x(7 x10 ) πR 3 M Water has a density of 1 g/cc Lead 11 g/cc Gold 19 g/cc 100,000 times density of gold! NOT NORMAL MATTER!! 1 cubic centimeter masses one ton! Surface Gravity GM 7 x10 −11 x 2 x1030 6 2 a= 2 = = 3 x 10 m / s R (7 x10 6 ) 2 This 300,000 gees If you weigh 150lbs on Earth, you would weigh 45 million pounds on a White Dwarf! What would happen to you and your spaceship? Escape Velocity 2GM 2 x6.7 x10 −11 x 2 x1030 13 6 Ve = = = 4 x 10 = 6 x 10 m/s 6 R 7 x10 Speed of light is 3x108 m/s, so escape velocity is .02c. Chandrasekhar Limit A peculiarity of Degeneracy Pressure is that it has a maximum mass. Each electron added must find its own quantum state by having its own velocity. But what happens when the next electron has to go faster than light? The Chandrasekhar Limit for a White Dwarf is 1.4M~ No White Dwarf Can have more than 1.4M~ Otherwise it will groan and collapse under its own weight. We’ll come back to this later. WDs are Common Every star with less than 5M~ will end up as a White Dwarf Most stars with mass above 1.3M~ have reached end of MS life. White Dwarfs are VERY common ~ 10% of all stars Closest is only 2.7pc away. (Sirius B) Will become increasing common as universe ages. Immortal Stars Regular stars need thermal pressure to balance gravity, and they need nuclear reactions to maintain the pressure, so the die when they run out of fuel. Not so White Dwarfs. They are as stable as a rock. Literally. A quadrillion years in the future all the stars will be gone, but the White Dwarfs will still be here. Their glow is fossil energy left from their youth as a regular star. Might die in 1031 years if protons prove to be unstable themselves. That’s 10,000,000,000,000,000,000,000,000,000,000 years! Really don’t know if universe will still be here. Binary Stars • • • • • • Optical Double appear close together but aren’t really binary Visual Binary orbiting, but we can see them both Astrometric Binary proper motion wiggles to show orbit Spectrum Binary spectra of two stars of different type Spectroscopic Binary Doppler shift shows orbital motion Eclipsing Binary light varies Half of all stars are in binaries…. Binary stars are formed at birth. Both components will have same age and composition. Can vary in mass Can be very distant (0.1pc) or touching Spectroscopic Binary Variable Stars Some stars just expand and contract. Eclipsing Binary Algol – “The Devil Star” Close Binaries Equal Energy Curves Gravity Mid-Point Contact Binaries Very Close Touching Common Envelope Two Nuclear Cores “W Ursa Majoris” star Mass Transfer Binary Accretion Disk Material Swirls In Friction allows the material to fall and heats while it falls. All the way to the surface Energy Released GMm 6.7 x10 −11 x 2 x1030 x1 E= = = 2 x1013W / kg 6 R 6 x10 Huge amounts of energy are released as the material swirls in. Material get hot. Really hot. Like a million degrees Kelvin. Emits ultraviolet and x-rays. We can see these accretion disks with x-ray telescopes! A Newtonian Black Hole Energy Falling To Surface Kinetic Energy GMm 1 2 = mv 2 R OR 2GM R= 2 c if v=c Schwarzschild Radius 2GM R= 2 c Two errors cancel. This is the radius of the “Event Horizon” The event horizon is a true singularity in space-time. It is a place where time and space cease to exist. Properties - Size 2GM R= 2 c R= 2 x6.7 x10 −11 x 2 x1030 (3x10 ) 8 2 = 3000m The radius of a black hole is 3km per solar mass There is no limit on size or mass. Note: Volume rises as the cube of the mass. Implies the larger the black hole gets, the lower is its density. A sphere of water the size of Saturn’s orbit would be a black hole! Properties – Escape Velocity No way. Not even light can escape. No signal can escape No particle Nothing Properties – Orbital Period 2πRS 6.28 x3000 P= = = 60 μs 8 c 3 x10 Material orbiting a black hole will have milli-second periods Properties - Basic 1. Mass (Schwarzschild Black Hole) 2. Electric Charge (doesn’t happen) 3. Angular Momentum (Kerr Black Hole) 4. Thermal Temperature No “Surface” Features No Magnetic Fields No Pulsing “No Hair” Properties – Energy Emitted • Energy Released from accretion • about 0.1mc2 Time Dilation δt = δt∞ RS 1− r Some event takes δt∞ out in free space. Same event takes place at radius r from center of a black hole. Now view it from free space. Takes δt instead. Longer. It looks like things are moving slower. If you are near the black hole, the rest of the universe appears to be moving faster. Time Dilation δt = δt∞ RS 1− r As r approaches Rs δt gets longer and longer. When r reaches the event horizon, time stops. We know how to make a time machine with a forward switch only! Just fly to a black hole and orbit above the surface. But you can fall in really fast as viewed from outside. Hawking Radiation The vacuum makes pairs of electrons and positrons that pop into existence and then annihilate without any net effect. Above a black hole, one can get sucked in. The other annihilates above the surface to cause radiation. Since its close to the surface, the light gets redshifted escaping, but it carries energy with it! 100 Billion Stars Orbital Period R3 (10000 x3 x1016 ) 3 15 8 = 6.28 x = 3 x 10 s = 10 years P = 2π −11 12 30 GM 6.7 x10 x10 x 2 x10 Takes the Sun 200million years to orbit Milky Way. Sun is 4600 million years old. The Sun is 23 Galactic Years Old. Milky Way – Edge-On Formation of Milky Way • Analogous to formation of the Sun • Start with big blob of gas • Let it collapse Disk Stability Again Globular Clusters Gas has friction and collapses to disk. Stars have huge momentum with small cross section. When a star forms it remains frozen in its initial orbit forever. Little knots of high density are first to form into stars. These are the globular clusters. They each contain a million stars. There are about 100 orbiting the Milky Way. Black Hole in Milky Way Dead Center in the middle of the Milky Way. 2.7 Million Solar Masses! Rotation Curves Winding Problem In under a billion years spirals would be wiped out. Spiral Density Waves Interstellar Medium • 10% of normal matter in gas – 90% stars • New stars form from this gas • Fundamental Part of the evolution of galaxy • Very Dynamic Place Reflection Nebulae HII Regions Star Forming Regions High Density leads to high star formation Dust Cloud • Dust forms from C,O,Si,Fe etc. • Like dust storm at sunset • Reddens stars beyond Molecular Clouds Dust in Space Dark dust clouds Very cold in the middle & shielded from UV Molecules Form H, C, N, O H2 H2O NH3 CH4 Even Ethyl Alcohol! Bubbles Stellar Wind Interstellar Gas Supernova Remnants • Four Phases • • • • Free Expansion 200 years Energy Conserving 10,000years Momentum Conserving 100,000 years Confusion 1,000,000years Super Bubbles Shock Wave Hot Bubble New Stars Form Superbubble Grows Takes Millions of Years to Grow Galactic Fountain Hot Material Churns Upwards Rains back down Galactic Halo Galactic Fountain Much like a bubble bath Local Group MW M31 Magellanic Clouds M33 M31 The Great Nebula in Andromeda M33 The Third Wheel of the Local Group Our Region 15,000,000pc Local Group Virgo Cluster M81,82 Hubble Sequence (not an evolutionary sequence!) Rotation Curves Without Dark Matter Hydrogen emits a radio emission line at λ = 21cm Doppler shift allows us to measure orbital velocity of gas clouds vs radius Dark Matter Mass to Light Ratio: Mass in Solar Masses divided by Luminosity in Solar Luminosities Sun has M/L of 1 (by definition) Rigel M=20 L=2000 --Æ M/L = .01 Pros Cen M=.1 L = .001 Æ M/L = 100 Galaxies typically have M/L of 7 to 10 Something like 85% of the mass is dark matter Dark Matter Dark matter is in Ball Æ We can measure its distribution even though we don’t know what it is. Dark Matter Regular Matter What is Dark Matter? WHAT IS DARK MATTER????? Some possibilities: Ionized Gas Small Stars Planets Baseballs Black Holes Neutrinos Neutralinos A flaw in Newton’s Laws MAssive Compact Halo Objects (Machos) Weakly Interacting Massive Particles (Wimps) Astronomers don’t know what most of the matter in the universe is! Cluster of Galaxies CD Galaxy A Galactic Cannibal M87 has eaten 100 of its own. The Distance Scale All the things astronomers have done to gain a handle on distance Parallax to 100pc I year cycle Main Sequence Fitting to 55,000pc Plot enough stars and the Main Sequence becomes clear. This works out to Magellanic Clouds. Beyond that, MS stars too faint Period-Luminosity Relationship Cepheids are bright and can be seen at very large distances. Type I Supernovae All Type Ia supernovae are the same brightness. That white dwarf that implodes and then explodes is always about the same. And they’re bright. You can see them at billions of parsecs! Apparent magnitude can be converted to distance. Redshift of Galaxies Hubble found that galaxies are redshifted. The absorption lines are those of the stars that make up the galaxy. Hubble’s Law The more distant the galaxy, the greater the redshift. The more distant is the galaxy, the faster it is flying away from us. v = H 0d H0=70 km/s/Mps A Modern Hubble Diagram Expanding Universe Current Universe Early Universe The volume of the universe is increasing. The Age of the Universe v = Hd ⎛1⎞ d = ⎜ ⎟v ⎝H⎠ d = vt Notice: At time zero, d = 0 All galaxies are at zero distance! The universe has zero volume! when t=1/H The Begining 1 t= H0 H = 70km / s / Mpc = 70 x1000m / s /(3 x1016 x10 6 m) = 2.3 x10 −18 s −1 1 17 H= = 4 x 10 s = 13Billion _ years −18 2.3 x10 Before 13 billion years ago, there was no before. Time and space started with the Big Bang We will return to this in a few more lectures The Cosmic Web The Redshift λ − λ0 z= λ0 z = 0 implies local z of 1 or more implies near far edge of universe Seyfert Galaxies Quasar QUAsi Stellar Radio source Æ Quasar (Sometimes QSO) Completely enigmatic for 1960-1980 Jets Cygnus A Full Model Superluminal Expansion Radio interferometers see blobs emitted by AGN’s from base of jet. Watch them expand. Know distance, so can measure speed. v = 900,000km/s v = 3c Superluminal ! ? Is Einstein’s ghost worried? The Intergalactic Medium The Cosmic Web Structure of the Universe Where is the center of the Universe? Where are the edges? What happens if you fly to the edge and stick your finger through? Newtonian Universe must be infinite. Cosmological Principle: The Universe is Everywhere the Same (when averaged over grand scale) Cosmological Principle • Cosmological Principle applied to expanding Euclidean Universe • New matter must be formed of nothing to keep density everywhere the same. Olber’s Paradox If universe is infinite with stars everywhere, then there an infinite number of stars. Any line of sight will eventually intersect the surface of star. Sky would be as bright as the surface of the Sun. Well it isn’t. So why not? Geometry of Universe Space Curves in on itself There’s no path out! Negatively Curved Universe Its warped so it cannot close back on itself. Is infinite in extent. Open vs Closed Universe is either open or closed. If closed: Positive Curvature Finite Mass Finite Lifetime Finite Volume If open: Negative Curvature Infinite Mass Infinite Volume Infinite Lifetime That’s INFINITY Folks!!! Astronomers have prejudice in favor of closed universes. All measurements have been inconclusive. We live near the edge! Critical Density • Whether Universe is open or closed depends on the average DENSITY of matter. • Above 10-29 g/cc the universe is closed • Below 10-29 g/cc the universe is open • We are very close to that density • Coincidence? ρcrit is about 1 atom per liter History and Fate of Universe Universe is one of these (maybe). Best Guess Size • Diameter of Universe is about 1024 times larger than the part we can see. • That makes the volume 1072 times larger. • But still finite • How big is 1072 ? Heat Death of Universe • • • • If universe is open, then it will last forever But stars will all burn out 1014 years Protons decay 1031 years Orbits will decay into black holes at center of the galaxies 1060 years • Giant black holes evaporate 10100 years • Nothing left but redshifting photons More on Infinite Universe • If Cosmological Principle holds and universe is infinite, there’s infinite mass. • Infinite Planets • Infinite Earth-like planets • Infinite planets just like you. • Infinite You’s • Far away: About 10118 10 meters away The Origin of it All? • Good Question • Perhaps a bubble in a hyper-universe • Perhaps its “unknowable” • But it appears Universe started as a very tiny bubble. How small, we don’t know. The “Planck Era” • When quantum fluctuations exceed the radius of the universe our theories are definitely inadequate. • R < 10-35m • t < 10-44 seconds • Density of Universe > 1093 g/cc • T > 1032 K • Then it starts to expand and cool…. The Inflationary Universe • Idea: Vacuum of space-time created with excess energy Æ folded upon itself • At t=10-37s, T=1028K, starts to relax • From 10-37 to 10-33s it expands by the creation of new space. • Universe expands from 10-28m to 0.1m • That’s 10cm in 10-33s = 1032m/s v = 3x1023 c !!! The Annihilation Era • After inflation settles down and resumes normal expansion • So hot that matter and anti-matter are in equilibrium. • For every 100,000,000 antimatter particles, there are 100,000,001 matter particles. • Basic Asymmetry From Planck era is not understood, but it’s why we’re made of matter. .001 Seconds • Jump from 10-33s to 10-3s • T = 1012K • Neutrons and Protons now have cooled so that can annihilate with anti-neutrons and anti-protons. • Leave mostly photons and an occasional particle of matter. 1 Second • Electrons and Positrons have cooled to point where they are no longer in equilibrium. T=1010K • Create photons. • One matter particle in hundred million is left. • Those are today’s electrons. Era of Nucleosynthesis • T = 109 K • t = 100s • Hydrogen and Helium form from neutrons and protons. • Tiny amounts of Li and Be are created. • No carbon: density too low for triple alpha • This is when the initial elements form The Plasma Era • From 100s to 100,000 years universe is a soup of ionized hydrogen and helium • But its expanding and cooling • Ends at 100,000years when the temperature falls below 3000K. • Hydrogen and Helium nuclei combine with electrons to form neutral atoms • At that moment, universe becomes transparent Sky Aglow • At moment of de-ionization, sky is glowing as blackbody at 3000K (M star) • Photons released are no longer re-absorbed • They travel into the universe and are travelling today • But they redshift. • Now 1000 times longer wavelength than then (makes them microwaves) The Cosmic Microwave Background • Microwave Antenna at Bell Labs – 1965 • Penzias and Wilson • Microwaves coming from sky, but not Earth. Uniformly • Predicted as part of a “Big Bang” by Gamov in the early 1950’s • Inescapable proof of the “Big Bang” • Killed all steady state theories • Now we’re studying it. At 100 Million Years • No Galaxies yet – or perhaps protogalaxies • Gas mostly smooth through universe • Clumps cause gravitational spots that create even greater density fluctuations. • Size: • Remember: Dark matter dominates Primordial Density Enhancements Grow • Now (12.4Billion years) we have structure • Galaxies and clusters Dark Energy • Expansion of Universe is Accelerating!!! • Implies New Inflationary Era (Why Now?) • Acceleration takes energy New Cosmology • • • • 70% of mass is Dark Energy (E=mc2) 25% of mass is Dark Matter 3.5% of mass is in Intergalactic Medium 1.5% of mass is regular matter in galaxies • Together they add to exactly critical density. • We’re right on the edge of open/closed • Universe is either finite and very big, or infinite.