Introduction to the Universe
Introduction to the Universe ASTR 1000
Popular in Course
verified elite notetaker
Popular in Astronomy
This 28 page Study Guide was uploaded by Adelia Adams on Monday October 12, 2015. The Study Guide belongs to ASTR 1000 at Georgia Southern University taught by James Higdon in Fall. Since its upload, it has received 45 views. For similar materials see /class/222011/astr-1000-georgia-southern-university in Astronomy at Georgia Southern University.
Reviews for Introduction to the Universe
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/12/15
Study Guide For Exam 1 Astro 1000 Fall 2008 This test will cover Lectures 16 the Nature of ScienceAstronomy the Changing Night Sky the Earthlike planets and Jupiter No calculators or electronic gizmos will be allowed none needed Strategies for preparation 1 Study the lecture notes and identify the major points 2 Study the chapters in the book amp read the chapter summaries 3 Work the ReviewDiscussion amp Conceptual Self Tests at the end of each chapter Lecture 1 Introduction to Astronomy What is Astronomy What does it deal with What does it try to explain 2 Why can one consider Astronomy to be the most inclusive science Why wouldageologist nd J 39 quot A quot 39 39 A computer scientist LA What is a Scienti c Theory What must it be able to do answer make precise amp testable predictions must be expressed in mathematics should be elegant should clear up lots of old questions amp lead to lots of new ones 4 Can you prove a Scienti c Theory How many experiments does it take to do this If you can t ever prove a theory then how does science make any progress at all Lecture 2 The Night Sky parts of Chap 8 1 What things do you see when you look up in the sky on a dark night Stars Planets the Milky Way comets 2 Why does the sky change from hour to hour From month to month LA What is special about the star Polaris 4 What are Constellations Are the stars in a constellation physically related How old are the constellations that appear in cave paintings UI Why do we have Seasons Why are the seasons reversed in the two hemispheres ie December means winter in Chicago but summer in Sydney Australia ON What are Solar Eclipses What are Lunar Eclipses Be able to explain how they are produced What did the ancient Greek scientists correctly deduce about the Earth based on observations of Lunar Eclipses 7 What is a Light Year Lecture 3 Intro to the Solar System amp The Earth parts of Chap 8 What is the de nition of a planet 3criteria given in class N What are the two families of planets in our solar system 3 What is the Central Problem in Astronomy answer guring out the Distance to something in space Once we have a distance many other properties can be determined 4 How do we measure masses of objects answer if they have something orbiting it UI The Earth s Interior Structure What are the four main regions crust mantle outercore innercore Describe their basic properties solid or molten Composition Temp The innercore would be liquid due to its high temperature 6000 K if not for the high pressure which squeezes it into a solid 6 How do we learn about the Earth s interior structure analysis of seismicwaves Earthquakes 9 seismicwaes P 7 or primary or Pressure waves Upampdown disturbances S 7 or secondary or shear waves Sidetoside disturbances P waves can travel through solid amp liquid rock S waves cannot travel through liquid rock 7 The Earth s Composition Changes with Depth Differentiation Why 8 Continental Drift How was continental drift rst discovered What is it What powers it How fast do the continents move on average Does this mean that continents are constantly changing position What happens when plates collide mountain rangesearthquakes What happens when plates move apart volcanoes What happens when plates brush by each other earthquakes 9 The Earth s Atmosphere know its basic composition 78 Nitrogen 21 Oxygen 09 Argon trace amounts of C02 amp water vapor how does the Atmosphere s height compare with Earth s radius know what Ozone is What does it protect us against How What is Ozone Depletion What causes it Why is this a big deal A 6year old asks you Why is the sky blue You answer 10 The Greenhouse Effect or Small Amounts of C02 amp H20 9 Big Impact know how the Greenhouse Effect works how different would the Earth be if not for the Greenhouse Effect what would happen if you start increasing the levels of atmospheric C02 ie Global Warming 11 The Earth s Magnetic Field amp MagnetoSphere what do we think generates the Earth s magnetic field what is the magnetosphere and Solar Wind How do they interact magnetosphere traps highenergy charged particles being emitted by the Solar Wind which streams away from the Sun what are the aurora Northern amp Southern Lights Why do they glow if not trapped by the Magnetosphere what would these highenergy particles do to us on Earth s surface Lecture 4 Mercury The Planet Nearest the Sun parts of Chap 8 l Orbit and Basic Properties orbit is very elliptical not a perfect circle l4Lh the Earth s diameter 5 ofthe earth s mass similar density implies what about likely composition very hot surface 2 Surface heavily cratered no signs of water weather or atmosphere Ever 3 Atmosphere None How can we explain this hint Vavg lt 017 Vesc what is the Escape Velocity Vavg and what factors in uence it 4 Magnetic Field Weak but definitely real None was expected 5 Surprise Mercury recently discovered to have a molten i e liquid interoirl This molten interior most likely generates the magnetic field via a dynamoeffect just like on Earth Lecture 4 Venus Earth s Evil Twin Chap 9 l Orbit amp Rotation very circular like Earth s 03 AU at closest Venus spins on its axis very slowly amp in opposite direction from other Earthlike planets prob Collided with another object very soon after formation 4 billion years ago 2 Basic Properties similar to Earth in mass diameter density ie twin of Earth atmosphere present 3 Atmosphere composition 96 C02 no oxygen 7 nearly all greenhouse gases mass 9times more atmosphere than Earth surface pressure amp temperature high amp hot 4 RunAway Greenhouse Effect on Venus explain how this came about as a result of Venus being closer to the sun and how it resulted in high surface temperatures 5 Surface of Venus mapped accurately by orbiting radar overall atter than the Earth no crustal plates No continents or continental drift Large craters visible on radar but few small craters Overall only 110 the cratering of Mercury or the Moon Why 6 Evidence for Volcanic Activity on Venus recall the radar images of volcanoes recall the radar images of lava ows recall the radar images of lava domes what is the evidence of ongoing volcanic activity changing SO in atmosphere possible lightning near volcanoes 7 Venus Magnetic Field surprise no magnetic field why not hint Venus rotates very slowly 8 Venus appears to have repaved its surface with lava 300 million years ago buried most of the craters under lava certainly the small ones Lecture 5 Mars The Red Planet Chap 10 l Orbit Rotation amp Basic Properties of Mars Mars has an elliptical orbit Martian day is 24hours Mars rotational axis is tilted like Earth s 9 Mars has Seasons Mars is N 12 the Earth s diameter Mars is N 110 the Earth s mass Mars average density is signi cantly lower than Earth Venus amp Mercury what can you conclude from this Mars has an extremely thin atmosphere 2 Surface of Mars Volcanoes the biggest in the solar system Craters splosh craters common Mariner Valley not a real canyon 7 ie not formed by water no crustal plates Crust is one piece No continents or continental drift Mars surface divided into two halves Northern Plain at low elevation few craters Southern Highlands rugged high elevation lots of craters Running water on Mars What is the evidence Gullies at crater edges ash ood ows ancient rivers Where did the water go Polar Ice Caps composition how they change with the seasons both polar ice caps are actually two ice caps in one How is this the ice caps are frozen C02 and H20 during a summer does the water ice cap disappear 3 The Atmosphere of Mars composition mostly C02 like Venus Mass extremely thin atmosphere not much protection from meteorites temperature and density cold and thin 4 A Runaway Greenhouse Effect in Reverse be able to describe this process ie greenhouse gases taken out of the atmosphere 5 Life on Mars The three experiments of Viking I amp 11 what were they what was so important about the sterilized sample from Earth Were the Viking experiments conclusive one way or the other Did they produce a de nite yes or no to the question of life on Mars It was claimed that fossilized Martian microbes were present in rocks that had been blasted to Earth after a meteor strike Why are these claims controversial Is the jury still out 6 The Martian Moons composition do they have the same composition as the planet Mars where are they thought to have arisen How did they wind up going around Mars They are very small and heavily cratered Lecture 6 Jupiter the King of the Planets Chap 11 1 Be Familiar With Orbit Rotation amp Basic Properties of Jupiter Jupiter is the largest planet in the Solar System Jupiter is 11X larger than the Earth Jupiter is not a perfect sphere but slightly attened at the poles This means it is not as solid as the Earth is but partially gaseous Jupiter is 300K more massive as the Earth 9 Jupiter s mass is twice that of all the other planets combined Jupiter s density is low 13 gcm3 This is not very far from the density of water 10 gcm3 Jupiter s magnetic eld is 20000 times stronger than Earth s Jupiter has lots of moons 61 at last count 2 Know the Composition amp Features in Jupiter s Atmosphere composition mostly Molecular Hydrogen Hz 86 amp Helium 138 with small amounts of methane ammonia amp water Jupiter s atmosphere is made up of alternating colored bands of clouds their colors arise from compleX chemical reactions taking place there many hurricane cyclone like storms are visible in Jupiter s atmosphere the largest of these storms The Great Red Spot Great Red Spot has existed for at least 300years it s diameter is 5X larger than the Earth what powers the Great Red Spot is still unknown 3 Understand the Basics of Jupiter s Internal Structure We know very little of Jupiter s interior But it is probably 1 rocky core 2 metallic hydrogen mantle 3 outer layer of molecular hydrogen and 4 the atmosphere we see 4 Jupiter s Magnetosphere Jupiter has a strong magnetic eld it rotates rapidly 10hour day and is believed to originate in the extensive metallic hydrogen layer the metallic hydrogen layer in Jupiter plays the role that the molten metallic Study Guide For Exam 2 Astro 1000 Fall 2008 This test will include the second half of Lecture 6 magnetic eld amp moons of Jupiter to Lecture 1 1 Radiation No calculators or electronic gizmos will be allowed none needed Strategies for preparation 1 Study the lecture notes and identi v the major points 2 Study the chapters in the book amp read the chapter summaries 3 Work the ReviewDiscussion amp Conceptual Self Tests at the end of each chapter Planets in General 1 Remember the definition of a planet 3criteria given in class What are the two families of planets in our solar system how do they differ in terms of size density chemical composition rings number of moons location in solar system make a table N Lecture 6 Jupiter the King of the Planets Chap 11 a Galilean Moons of Jupiter who discovered the Galilean Moons know their basic properties compare them to Mercury what is special about 10 what is interesting about Europa amp Ganymede what s interesting about Callisto what sort of mission is NASA planning for the Ice covered moons what might they be looking for b Jupiter and Comets Jupiter has absorbed millions billions of comets and asteroids some that might have collided with Earth Comet ShoemakerLevy in 1994 was an amazing example see Saturn lecture ShoemakerLevy was captured by Jupiter s gravity 200 years ago in 1992 it came within Jupiter s Roche Limit and brokeup into 20 kmsized pieces these impacted Jupiter s backside in l994 releasing huge amounts of energy Fireballs seen rising over Jupiter s edge Lecture 7 Saturn the Ringed Planet Chap 12 a Be Familiar With Orbit Rotation amp Basic Properties of Saturn Saturn s orbit is fairly elliptical distance varies between 90 7 101 AU Saturn is the 2quotd largest planet in the Solar System Saturn is 9X larger than the Earth Saturn is more squashed in shape then Jupiter implying that is more gaseous then Jupiter and much less rocky than the Earth Saturn is 95X more massive as the Earth Saturn s average density is less than water 7 07 gcm3 It would oat in water if you could build a big enough bathtub Saturn s magnetic eld is 1000 times stronger than Earth s Saturn has lots of moons 31 but not as many as Jupiter Most are very small Saturn is famous for its beautiful rings b Saturn s Atmosphere composition very similar to Jupiter s with one exception Saturn has much less Helium in its atmosphere than Jupiter aloes the helium has condensed into droplets in Satum s outer atmosphere and rained down to lower levels Saturn s atmosphere also shows alternating colored bands of clouds but the colors are much more subdued Less colorful than Jupiter hurricane cyclone like storms are present in Satum s atmosphere but they are more difficult to see 9 Nothing like Jupiter s Red Spot on Saturn a giant hurricane like storm has been observed at Satum s South pole d Saturn s Internal Structure Like Jupiter we know very little of Satum s interior But it is probably 1 rocky core 2 metallic hydrogen mantle 3 outer layer of molecular hydrogen and 4 the atmosphere we see e Saturn s Magnetosphere Saturn also has a strong magnetic field due to its rapid rotation and metallic hydrogen core 71000 times stronger than Earth s Saturn also has Aurora Northern amp Southern Lights f Saturn s Rings Saturn is surrounded by a system of very bright rings visible from Earth since Satum s aXis is tilted 267 degrees the rings look different during Satum s 294year orbit around the Sun the rings are extremely thin 7 only a few meters in places the rings are composed of large numbers of bits of debris sizes range from sand grain to tens of meters On average snowball sizeal the debris is coated in water ice which explains why they are so bright the rings are actually thousands of small ringlets The outermost ring Fring appears braided and is kept in place by two small Shepherd Moons The rings exist within a zone called the Roche Limit 9Any object held together by gravity straying inside the Roche Limit will be crushed into rubble by Satum s gravitational eld origin of the rings unknown not likely to have formed with the planet 4billion years ago ie the rings are not thought to be ancient one possibility icy debris chipped off Satum s moons by impacts may collect in to the rings and stay there another possibility an ice rich small moon of Saturn strayed within the Roche Limit and got crushed into rubble Lecture 8 Uranus Neptune amp Pluto Chap 13 parts of 14 a Orbit Rotation amp Basic Properties of Uranus amp Neptune Uranus orbit is fairly elliptical 1820 AU Neptune s is very circular Uranus amp Neptune have nearly identical diameters 4X larger than Earth Both have average densities similar to Jupiter s l5 gcm3 Uranus aXis is tilted into its orbital plane 7 it s laying on it s side 9 Uranus has extreme seasons 40year winters amp 40year summers at the poles 9 During winter the Sun is never visible During Summer the Sun never sets at the pole Neptune has a 29 degree aXis tilt giving it seasons like Earth Uranus takes about 84 years to orbit the Sun Neptune takes l63years both have 10 of moons Neptune generates 3X more energy than it receives from the Sun How Uranus discovered accidentally by William Hershel with his telescope Neptune discovered using mathematics Uranus orbit seemed funny as if another more distant planet were tugging on it Calculations said mystery planet would be found at a certain location which is where Neptune was situated b Uranus amp Neptune s Atmosphere composition of both are very similar Both similar to Jupiter amp Saturn molecular hydrogen 84 Helium 14 Methane 23 blue color of both is due to Methane in atmosphere which readily absorbs red photons from the Sun Neptune shows Jupiterlike storms including a Great Dark Spot that disappeared in 1990 s c The Wackv Magnetic Fields of Uranus amp Neptune magnetic elds are not centered on the planet cores neither point along the rotational axis d Internal Structure of Uranus amp Neptune both are thought to have rocky core iceliquid slush layer and a molecular hydrogen layer no metallic hydrogen layer in Uranus or Neptune as pressure is too low how might this explain their peculiar magnetic elds e Uranus Rings discovered accidentally by ying IR telescope Kuiper Observatory very skinny like Satum s Fring at least one pair of Shepherd moons f Neptune s Rings three very faint rings g Pluto s Discovery at first it appeared another more distant planet was perturbing the orbit of Neptune Calculations indicated the location and American Clyde Tombaugh found the planet Pluto with an optical telescope actually the calculations were in error there were no problems with Neptune s orbit and Pluto was discovered purely by chance h Properties of Pluto Pluto is small 20 the size of the Ealth and much less massive Pluto s density is 40 of Earth s 9 21 gcm what does this tell you Pluto has three moons 7 Charon plus the newly discovered Pl amp P2 Pluto s orbit is most elliptical in Solar System d 3049 AU from Sun Pluto s orbital plane is l7degrees out of the Solar System at times ie 19791999 Pluto was closer to the Sun than Neptune i Nature and Origin of Pluto why do many astronomers hesitate to call Pluto a planet How is Pluto different from the other planets Is Pluto a moon of Uranus that was kickedoff during a collision problem then how did it acquire its own moon No moons have moons astronomers now consider Pluto to be a new class of object 9 Dwarf Planet Pluto may simply be one of the largest members of this new class ie the dwarf planet UB3 13 aka Xena is slightly larger than Pluto several dwarf planets also have their own moons ie UB3 13 there may be hundreds like Pluto and UB3l3 in the Kuiper Belt Do we want to call all of these objects planets Lecture 9 Space Junk Aster0ids Comets amp Meteors Chapter 14 a Asteroids History amp Properties know what Bode s Law is and that it predicted a planet 28 AU from the Sun ie between Mars amp Jupiter Giuesppe Piazzi priest amp astronomer found Ceres 1801 200000 eventually discovered between 233 AU ie the Asteroid Belt too small for planets they are called Asteroids starlike bodies all the asteroids taken together would not have the Moon s mass know the differences between the three types of asteroids Ctype carbon rich Stype silicon rich Mtype metal rich know what the Earth Crossing asteroids are and why they are a concern hint remember Comet ShoemakerLevy what would happen if a 10m asteroid slammed into the Earth what would happen if a 150m asteroid slammed into the Earth what would happen if a 10 km asteroid slammed into the Earth know how asteroids look from flyby missions irregular shaped super space potatoes with lots of craters How do they compare with the moons of Mars Know the two leading explanations for the origin of the Asteroids l they are the remains of a destroyed planet 2Jupiter prevented them from ever merging into a planet Which one is the best explanation and why hint mass amp composition b Comets History amp Properties comets are basically 5 10 km sized snowballs with gravel amp dust 9 ie Dirty Showballs remember that comets were viewed as bringers of bad news know how the orbits of comets differ from planets extremely elliptical know the difference between Long Period Comets travel thousands of AU from Sun taking thousands or millions of years to orbit the Sun once Come from the Oort Cloud Short Period Comets orbits extend out to maybe Pluto take far less time to orbit Sun eg Halley s Comet every 76years Come from Kuiper Belt know the basic components of a comet nucleus coma dust tail ion tail understand why a comet changes appearance as it moves towards the Sun c Meteors 7 Shooting Stars know the difference between meteors amp meteorites understand how meteor showers arise from the destruction of a comet d Chicxulub and the End of the Dinosaurs what is the CretaceousTertiary boundary What date does it correspond to What major group of creatures disappear in crossing this boundary the thin layer in between is rich in soot volcanic glass beads and what rare chemical element iridium is rare in the Earth s crust but abundant on what solar system bodies What is the Alvaraz Hypothesis How big is the Chicxulub crater Where is it located How is it tied into the demise of the Dinosaurs 655 million years ago How would a 10 15 km asteroid damage the Earth s ecosystem e Mass extinctions and Nemesis the fossil record shows periods in Earth s history when both the number of species and total number of living creatures decreases dramatically these events are called Mass Extinctions 7 life on Earth takes it on the chin Mass extinctions appear to happen every 2530 million years 7 Periodic and strangely repeatable Nemesis proposed small amp faint companion of the Sun Nemesis takes 2530 million years to make one orbit When Nemesis is at its closest to the Sun NIlight year its gravity field disturbs the orbits of comets in the Oort cloud some of these comets fall into the innersolar system one or two hit the Earth devastating the ecosystem and killing off many species problem nobody has ever seen Nemesis Some astronomers are looking Lecture 10 Theories of Solar System Formation and Other Solar Systems Chapter 15 a Scientific Theories of the Formation of the Solar Svstem what are the regularities in the solar system 1 all the planets lie in the same orbital plane 2 all the planets orbit the sun in the same sense as the Sun rotates 3 with 2 exceptions the planets rotate in the same sense as Sun 4 all Earthlike planets are in the inner Solar System 5 all Jupiterlike planets are found in the outer Solar System 6 the planets are widely separated from each other 7 Their orbits are very nearly circles 7 even Mercury amp Mars 8 The Kuiper Belt is in the plane of the Solar system 9 The Kuiper Belt also orbits the Sun like the planets b What is the Planetarv Capture Theorv of the Solar System Sun moves through space and captures free planets via its gravity What are the major problems with this idea can t explain why the planets amp Kuiper Belt are in the same plane can t explain similar rotation senses of the planets or why the rocky planets are all in the innerpart of the Solar System can t explain where planets come from why we haven t seen any c What is the Collision Theorv of the Solar Svstem Another star collided with the Sun the solar system formed out of the debris What does this idea explain example may explain why all the planets are in one plane What is the chief problem with this idea hint collisions between stars are extremely rare d Best Theory Solar Svstems form as a direct result of Star Formation be able to describe the overall process of star formation collapsing gas cloud 9 large disk of dust amp gas plus star Planets form out of leftover material in rotating disk be able to describe how planets can form out of a cloud of gas amp dust what is Condensation How can it explain the fact that rocky planets are found nearer the Sun while Jupiter planets are in the outer parts of the Solar System what is Accretion What role did it play in planet formation e The disk of gas amp dust around voung stars is called The Solar Nebula Have we found examples in space of them How are they located What do they look like hint look for stars showing excessive infrared emission 7 ie dust heated by the young stars f What are collisions needed to explain hint Venus backward spin Uranus lies on its side g ExtraSolar Planets how do we currently find them Direct imaging Why does this only work using infrared telescopes Best way so far Detecting the wobble of a star as planets circle it how many have we detected One Two Many more what sort of planets are they Are they Earthlike stars do these planets tend to be far away from their parent stars Very close do these other Solar Systems look like our Solar System If not what s ali erent Does this mean that our Solar System is unusual Understand what a selection e ect is Why is this relevant for solar system searches Lecture 11 Radiation Chapter 3 a IT J A Light as an ElectroMagnetic wave Wavelength 7t 7 distance between wave creststroughs Frequency v 7 how many wave crests pass by in one second Amplitude A 7 how high is the wave Energy E7E hvhc7t Speed c 186000 milessec 300000 kms b What is the ElectroMagnetic EM Spectrum Understand the differences between Radio Infrared Xray UV radiation ie their wavelengths and how much energy they carry c Energy of Light vs v v 39 39 M of Light The energy of light can be written E hc 7t ie energy is inversely proportional to wavelength bigger wavelengths carry smaller amounts of energy More energetic light has smaller wavelengths c What parts of the EM spectrum are blocked bv the Earth s 39 e d Understand what Blackbody Radiation is why is Blackbody Radiation important in astronomy Does Blackbody Radiation depend on chemical composition Density On Temperature How does emission from a Blackbody change as the temperature changes What is Wien s Law What does it relate Why is it useful lepeak constT What is Stephan Law What does it relate Why is it useful EnergyArea o T4 Example I have two identical bowling balls A amp B But ball B is ten times as hot as ball A Which one emits more energy per square inch Answer B from Stephan s Law How much more energy is emitted per square inch Answer 104 10X10X10X10 10000 times more energy is emitted per square inch by the hotter Blackbody chellenphygeorgiasouthern eduNjhigdon Study guides are 0nlin e Don t wait until the last second Trying to cram for a nal will result in a disaster The History of the Universe The Cosmological Principle I The Laws of Physics Relativity Quantum Mechanics Quantum Electrodynamics are the same throughout the Universe and do not change with time 9 This assumption is actually testable S 0 far the constants of physics do not seem to have changed to parts in a million since the observable Universe was N14 of its current age Field of view Galactic k plane South Galactic pole 2 The Universe is Isotropic on large scales That is it looks the same in every direction This must be true everywhere in the Universe 9 the number of galaxies galaxy clusters etc you observe per square degree is the same in any direction provided you look far enough away i e gt 300 Mpc The Cosmological Principle 3 0n sufficiently large scales 3 00 Mpc say the Universe should look the same everywhere That is the Universe is Homogeneous on large scales Redshift 010 Distance MP0 This assumption is consistent with best studies of structure on the largest scales there are no structures larger than N3 00 Mpc as far as we can tell Take a cube 3 00Mpc on a side and set it anywhere in the Universe The contents of this big box should be approximately the same The Cosmological Principle We don t know for sure that these assumptions are 100 correct everywhere However they are consistent with all current observations If we accept the Cosmological Principle several implications follow I There can be no edge to the Universe 9 Ifyou re at the Universe s edge you will count d erent s ofgalaxies in di erent directions Also a 300Mpc wide box inside the edge will not look the same as a 300Mpc wide box outside the edge 2 The Universe has no center 9 An observer at the center would see a di erent Universe comparedwith an observer somewhere else There is no preferred position in the Universe General Relativity General Relatxvxty m Emstem s theory afgravxty It helps descnbes the Umverse an largestscales quot39edwrli 2 WW mm 157 15 mu a General Relativity to m ave thes e smught mes are a enmity curv ed Mann 121k Watttime how to bendSpace 39mz elk 1 u e 4 WW Einstein s Field Equations You think you have math problems Einstein in a letter to a girl complaining aboutAlgebra A Static or Evolving Universe Einstein found solutions of the equations of General Relativity that were consistent with the then standard view among scientists the Universe is unchanging eternal amp static Hubble s Law and the Big Bang Hubble found and Lemaitre predicted that the further away a galaxy is the faster it appears to be moving away from us What does this tell us about the Big Bang Recessional velocity kms 30000 20000 10 000 5000 3000 2000 I 1 I 2 3 5 10 20 30 50 Distance to galaxy Mp6 Recall Recessional Velocity distance X HO Where H0 72 kmsMpc Hubble s constant Q How long has it taken a given galaxy to reach its observed distance Note this is true for w galaxy we could have chosen Hubble s Law inwlies that 14 billi0n years ago all galaxies were in the same place Where Was the Big Bang It is incorrect to think of the Big Bang as having taken place at some point in the Universe Rather the entire Universe matter energy spacetime was created in the Big Bang Recovering Hubble s Law Consider one of the coins galaxies on the inflating balloon Universe and the distances to two other coins one very close and one very distant Velocity DistanceTime The more distant galaxy B has moved a larger distance in the same time as galaxy A has This is Hubble s Law 9This will be true for any galaxycoin Redshift and recessional speed Absorption Lines from our Sun Lines from a distant galaxy Vrecession N C Z Re interpreting Redshifts We explained the redshift of galaxies i e spectral features shifting to longer wavelengths as a Doppler shift due to their motion wr to us This is wrong Photons traveling from distant galaxies have their wavelengths increased by the expansion of Spacetime It has nothing to do with velocities at all The redshi of a photon emitted by a distant galaxy measures the amount by which the Universe has expanded since that photon was emitted T he further it travels the more the Universe expands the more stretched out the photon becomes the longer its wavelength becomes Evidence for the Big Bang There are Three Pillars of evidence for the Big Bang One is Hubble s Law The second is the Cosmic Microwave Background radiation CMB A team at Princeton University started building a telescope to search for these photons Evidence for the Big Bang In 1964 two engineers Robert Wilson amp Arno Penzias are trying to identify and eliminate sources of radio noiseinteiference for US telephone service Using their funky sugarscoop radio antenna they notice a persistent hiss coming from all directions in space They tried and eliminated all sorts of possible sources for this hiss including fermenting bird droppings in the antenna They eventually realized that they were detecting photons left over from the Big Bang scooping the team at Princeton University amp winning the I 978 Nobel Prize in physics DIFFUSE INFRARED BACKGROUND EXPERIMENT FAR NFRAR39ED ABSOLUTE sPEcTRoPHoTOME IE 3 03 t MICROWAVE RADIOMEYER I INSTRUMENT AND SPACECHAFT ELECTRONICS v MICROWAVE RADIDMEYERS n r amp 1 w w I I T E 01 The solid line is a Blackbody spectrum T2 735 K g t to the C OBE data black dots T he t is g astonishingly good note the error bars are smaller E 001 than the size of the dots D 0001 Evidence for the Big Bang Stellar nucleosynthesis does a marvelous job of acctmnting for the abundances of heavy elements However there appears to be far too much Helium in the Univers 9Most helium could not have been formed in the interiors of stars It must have another origin neutron 9 deuteron IOUseconds after Big Bang T N10 K and Universefilledwith photons electrons 4 neutrons andprotons Protons outnumber neutrons 5to1 proton a a At these temperaturesdensities protons neutrgv proton by high energyphotons amp neutrons canfuse to make a deuteron hatan b But the deuteron ispromptly destroyed H I b Evidence for the Big Bang After 200seconds the Universe has expanded andcooled enough to allow deuterons to survive neutron Step 1 proton amp neutronfuse together resulting deuteron H n in a deuteron heavy hydrogen nuclei 4 proton deuteron Helium3 Step 2 deuterons can now live long enough tofuse together leaving a helium3 nucleus light helium 4 Step 3 for the next looseconds the helium3 nuclei can capture a neutron forming 4p a nucleus ofhelium O Helium4 Evidence for the Big Bang Helium production takes place for only a brief window in the early Universe from 200 sec to 3 00 sec after the Big Bang Afterwards the Universe has expanded enough to make it reduce the temperature and density below the levels needed to sustain these reactions Helium production abruptly stops after 300 sec deuteron Helium 3 Detailed calculations byAlpher amp Gamow showed that during this time one helium I nucleus forms for each I 6 protons I helium nucleus 12 protons I helium nucleus Helium 4 4 14 25 by mass 16 9 Indirect Evidence for the Big Bang I Quasars are currently extremely rare in the local universe But once they were very common I c 395 a tquot N 395 E m 6 m a c Q on a m a 5 0 H 04 06 Age of Unwerse to a 1 The F ormatt on of Structure The Early Universe was extremely uniform and homogeneous How did walls voids clusters and galaxies ever form out of this Clues came from an orbiting radio telescope Cosmic Mcrowave Background Explorer CUBE from the 1990s The Formation of Structure This map from COBE shows pattern of small temperature variations in the CMB radiation The CMB emission is actually remarkably uniform The variations visible above as blue amp red Splotches represent variations of N5 parts in 100000 or about 00001 K around the 2 7 K CMB These veiy small temperature MetalIlium represent and arise from uctuations 39 the matter distribution in theEarly Universe z 1000 The Formation of Structure COBE wasfollowed by another orbiting mission with higher angular resolution the Wilkinson Microwave Anisotropy Probe to look more closely at the CMB Temperature fluctuations visible in WMAP 6TT10395 pp 10394 Structures visible today have much higher density contrasts pp 103 rich galaxy clusters pp 106 massive galaxy The Formation of Structure The big question how do we get from a nearly perfectly homogenous early Universe to the very clumpy one we see all aroundus The answer extremely small over dense regions grew progressively denser under their own self gravitation Eventually these regions became dense enough to form the laments walls and voids and clusters of galaxies The Formation of Structure The Universe appears to have started as a mixture of mostly dark matter and ordinary matter A fewthousand years after the Big Bang the dark matter started to clump due to its own gravity The dark matter clumps grew into large scale structures laments walls clusters etc and ordinary matter flowed into it eventually forming galaxies 9 Dark matter formed the structures Ordinary matter followed its overall distribution Densny Dark matter i Normal many Space a Trme r second Densny Space b Time 1000 years Dark matter Ga axwesc uslers normal Density maner Space c Time 105 years 14
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'