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by: Ms. Adrian Buckridge


Marketplace > University of Florida > Astronomy > AST 1002 > DISCOVER THE UNIVERSE
Ms. Adrian Buckridge
GPA 3.72


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This 112 page Class Notes was uploaded by Ms. Adrian Buckridge on Friday September 18, 2015. The Class Notes belongs to AST 1002 at University of Florida taught by Staff in Fall. Since its upload, it has received 33 views. For similar materials see /class/206979/ast-1002-university-of-florida in Astronomy at University of Florida.




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Date Created: 09/18/15
Key Concepts Lecture 35 TheEarly Universe 3 Inflation and the very early Universe hob lans for the Standard Big Bang Theory 0 Horizon problem why is the Cosmic f39 1 I I I the same temperature in every direction 7 How did opposite sides of the observable Universe know about each other Flatness problem why is the density of the Universe so close to the critical value 7 Deviations away from the critical density grow an are ampli ed as the Universe expands so the present density requires initial conditions that were tuned VERY precisely to 1 part in 1015 I In ation Solves Horizon problem In ation GUT Grand Uni ed Theory phase transition 103935 seconds T1028K 7 Before all forces ofnature except gravity were the same uni ed T e nuclear strong force F4 I size or Lmverse my 7 Rapid expansion means entire observable universe was close together at one time 7 Thus the universe was causall connected The electromagnetic force iuquot s The weak force limestnce an Bang 7 A er transition strong force is no longer uni ed 0 False vacuum adds pressure to universe 7 Similar to super cooling water phase transition of liquid to solid energy is released 0 Universe grows by a factor of 1050 in 103932 seconds 0 o o o I a o 3939 IbVTmelOquot 5 Solves Flatness problem Curvature before in ation is expanded Grossly in ated unierse will be nearly at Radius 1048 m i Class website 9quot Discussion sections Tues ay penud41U4U7113U3mBryant3 Wednesday penud 8 3pm snpm Bryant 7 Thursday pmuds 1145mm 35pm Bryant 3 THE NEW SOLAR SVSIEM N Cords Saturn Nopluna t n uf cehr Thursday penud714Uper4UpmBryzn13 m znz i 39 i L g Telescope observing project see class website Homework 1 solutions on class website Homework 2 is on class website and is due 6pm Thur 18th Sept Midterm 1 is next week Thursday 25th Sept in class Other exam dates midterm 2 30th Oct nal 9th Dec Reading Intro Chapters 1 2124 41 5 ZWZZaSCLE iiifZiSZ Ji T Mars i Urnma Pluto Jupiter gt195quot gtP 9 Key Concepts Lecture 10 39 Tides as a consequence of Newton s Laws Recall Newton s Law of Universal Structure of the Earth Gravitation v Weight is the force of gravity pulling you Intro to Elements and Atomic Structure Radioactivity to the ground F constant X m m lth 39 you B 12 Evolution of Earth s Surface How much do you weigh on the Moon Spring amp Neap Tides sum Spnngquotodeswhzn5nnand smmm m n fmmwm rampmu canceleachathzrmn quotWWE 1 Jung m mm mm mmWh ananlydue m gnvnatmmlpu afthz Mann Sun39s effecnsabam 1mm slmng IMMWMWrng mmp kmnmw wnmmns m the Wm af odes rmm an m place MQQnigTd lt y O erm ng l EaI i J Mum mtates abuut um per munLh 5 that n aways 39 Dense Rucky Cmnpnsi nn presents the same facetu Earth Evnlving Surface muchisynungu man Inmany n misled faster but was sluwed dawn by udal 6m millinn yms fumes 39nm the Earth Atmnsphere nf Nitrnganznd Oxygm Theudes unthe Earth med by the Mum are 215 sluwmg dawn the Emh39smtanun the day s gemng n The Ea1th s Intenor mm hmym mpmmssm kgm 7 Wattxl lxm 7 Namancksm A kgm 72mm WW 7 stnnc ayzxs 7dznse mundsmks 13m mm nms mums mm Mm Emir mm Mummy M m km A mu am mm mm The Elements and Ammic Structure mh m Flank mg mg 5 cumsed mm durum e g Ham 1 Helmm 39le mm c Oxvgumol Imam em Amm Dmmxmm memrm Pzrd a me Nndnrdsuy e rmm mm m 4 1mm dam an RN myth m had MAM dauy sm x x 1mm Ssmmdz Dru Seeing Ins1de the Earth Inlenur strucmre xs pmbed by studying huw Waves Laval mmugh the Earth anhquakes gamma sasmm waves mama suund Waves me Lhs we mntell Earth has a hqmd Hula cure Imp o ance of Radioactive Decay anary source ofheat m the mtmor 7 Numbuarpmm 7 gram 7 same wuswmmwme mm my lua Used to devermme ages 7 murmmmsrmm mm clung um passes an 2mm ux S ha i g ktheGmsL Plate T ectumcsCunnnental Dn Vulcam aan Impacts Emsmn H at am Mmemdcaxe m Wumm a nesfmm h mmmmm am ummmrpdkd mm Pmcesstakesbmxms ufyears Evidence r r 0 Many volcanoes occur in regions where the crust is weakened by continental drift Some volcanoes are due to hotspots caused by rising lVIantle plumes e g Hawaiian island chain mu pm mlmnfsm um um It is not necessary to have m continental drift to have volcanoes 39 Objects Strike the earth I Gravity naturally attens the surface into a perfect sphere They create craters The craters are eroded and eventually subducted Wind water and ice slowly flatten mountains and craters Takes hundreds of millions of years Since the surface of the Earth is active it has only a few young craters left If the Earth was a geologically dead planet with no plate tectonics or atmosphere what would its surface look like today Key Concepts Lecture 18 Jovian Planets cont and Outer Solar System S aturn Titan Saturn Triton Neptune the smaller moons 19 satellites 7 7 satellites in regular orbits 0 Titan is the largest 0 Titan only one with atmosphere Uranus and Neptune 7 Several small moons orb1t near r1ngs 7 2 distant irregular satellites in retrograde orbit Beautiful set of rings Pluto and Dwarf Planets 7 broad amp at 7 huge collection of icy pieces in orbit around equator Titan Largest satellite of Saturn Titan s Atmosphere Active atmospheric chemistry Mostly nitrogen 7 Also some carbon monoxide methane ethane hydrogen cyanide cyanogen similar size mass amp density as Callisto composition rock amp ice W Substantial HST IR mumple 010 layers quot atmosphere methane 393 0 due to low temperatures may be liquid methane oceans uv Amerynu 1 Thick atmospheric surface pressure higher than Earth mum mm Huygens Probe Visits Titan Jan 05 Titan Earthlike geology chemistry involved is quite different 0 liquid methane instead of water 0 frozen water ice instead of silicate rock 0 hydrocarbon particles instead of dirt volcanoes spew very cold ice amp ammonia instead of lava ngs of Saturn 0 Rings are thin 20 m thick 39 3 broad bright rings 7 A B C 0 handful of narrow rings of which F is most substantial Gaps between rings Ring particles made up of ices and roc Small shepherd moons can create very narrow rings Tethys Uranus Ring amp satellite system are tilted a1 98 15 regular satellites 7 5 largest are comparable m size to moons of Satum 11 rings 7 marrow nbbons ofmatenal wrth broad gaps Pluto Dlseovered 1930 by Cly In 7 hrgaermelmauuhtu the eelmuethaa any plaaet 7 must ellmtaeal urhrt 7 urhrt emsseswrth the urhrt queptune 7 Or rt penud 248 years 7 very ta teal ams ufrutatmhlrke Uranus Ne tune tes 7 a regular satellrtes elusetu planet 7 z uregular satellrtes farther uut r Tntun urge segue arm has an atmsphere mm wleaheem ms ngs r nanuw amp famt Pluto cluhal Prupemes 7 Drameter722uuhm 7 Lawaehsrty7 mun kgm Has 1 satelllte r Charun 7 Dlametexr lzuuhh 7 Lawaehsrty7 lzun kgm nght am dark areas 7 Natelearwhueausesthem Plum ls vexth ta stuayheeause ar us great arstame lure seem a saeeerhall m Key Westrmm Gamesnlle As an ersnauvutz tu Planets of the Solar System Sim Em w mm rave mam n in u nm in v m writs mum Origin of Pluto Mercury I Different from Jovian planets 7 Not a gas giant too dense Probably icy Venus 31itjmlm 7 Very elliptical and inclined orbit Earth quot 3 r m Origin Mars 213 THERE r M was t39 39f ul s iiiLT WlTjSi A true planet Jupiter Marina lt rmquot quot 5 m l M W I Why no large amount of H amp He Saturn 53 a i md lnhclnlim Uranus m 4 warmed a mam m a m 5mm 7 Escaped moon of Neptune I Propem39es like a Jovian moon I BUT could not escape With satellite 7 Therefore probably related to Kuiper Belt Objects that formed independently in the outer solar system August 24th 2006 Historic day for astronomy I Why such an odd orbit NeEtune m that mm a man In lqu u in 5n H mm mm m of sew Astronomers name 39world of chans39 m HEW SOLAR srsrsn CQIQS Emh Neptune quottttTtg g TLT umnu Plulo l Jupller Vulus an m mm mm Dleu Key Concepts Lecture 17 Jovian Planet and Outer Solar System Overv1ew Rings and the Roche Limit All Jovian Planets have Moons Galilean Satellites of Jupiter 7 ngs 7 many satellltes Rings amp satellites orbit planet like minisolar system Composition of rings amp satellites I differs from objects in inner solar Pluto and KUIper Belt Comets system Titan Saturn Triton Neptune the smaller moons 7 temperatures in outer solar system much colder Orblts Most satellites of Jovian planets follow direct or regular orbits counter clockwise if viewed from above the north pole Ring systems are in regular orbits Irregular satellites 7 orbit in retrograde clockwise 7 or have highly elliptical orbits 7 or have highly inclined orbits 739 7 ts of Saturn s moons 39 Orbits Orbits give us information about the formation of the rings amp satellites Objects in regular orbits 7 probably formed at the same time as th planet 7 probably formed by processes similar t those that formed the planets Object in irregular orbits 7 probably formed far away and were capture an gs Particles follow Kepler s laws 7 inner particles orbit faster than those farther out 7 ring not rotating rather individual moonlets orbiting ifrirrg particles widely spaced move independently ifparticles are close gravitationally interact moons clear gaps irrrirrgs Rings 0 Rings consist of billions of small particles or moonlets orbiting close to their planet 7 size of particle ranges from grain of sand to housesized boulders Origin of Rings Breakup of shattered satellite Or remains of particles that were unable to come together and form satellite Gravity plays important role 7 differential force of gravity ie tidal forces 0 tear bodies apart 0 inhibit loose particles from coming together Roche Limit 7 Ring Formation mmdwmwrmnvuxc m wwmmnnmmmm mm Surface is canshndyclungmg Io s Volcanoes Variety ofvolcanic hot spots e large lavalakes made ofllquld sulfur Europa size amp density similar to oon mainly rocky composition e heat from Jupiter during early evolution evaporated mue dune lee smooth surface few impact craters Io s Volcanoes Why so much volcanic activity 39lldal heatingbanpiter other it from becoming tidally locked to HM Sm Jupiter Thus 10 is continuall mason Images stretched and pulled leads to heating Europa Surface isice covered extensiveampc0mplex network of cracks in i eintemal geological activity Europa qumd Water 15 rare m the Sular system Eumpaxs guud place m luuk fur extrartenestnal hfe Galilean moons ve awa an away 39nm Sun Ganymede at Callxsm Emma mgis knm mth mama may mum dnk mm myamm mmmgma mm mnmauvk a mmmmm dnkmkn x m Kmme mum mm mummy mmymd n m amaammm ms Wmmsm a mm m wins 15 mumw may x Jupiter s Rings 74 ngs dlscuvaed by Key Concepts Lecture 24 The Sun as aStar Nuclear Fusion the source of the Sun s energy Structure of the Sun and other stars Question Remember that the luminosity of a star was found be to related to its mass LOCM4 Now we know that stars get their energy by converting their mass directly into energy so the total amount of energy a star has is proportional to its mass EOCM Will a massive star live a longer or shorter time than a low mass star Answer given and described in class lecture Energy From Fusion Converting mass directly into energy is the most efficient way to get energy from matter If 10 of the Sun s Hydrogen is converted into Helium the Sun will shine at its current rate for 10 Billion Years 10 X 10er Nuclear Fusion The ProtonProton Chain mim quotm r Nam 11gt mm r v k 39 Wotan mrh i 26 x f u w Copyright o 2007 seam Prentice Haquot lne W 1s produces neutrinos The of the Stars arrange themselves to balance the forces Within them Gravity tries to pull all matter together Solar Neutrinos Neutrinos Very lowmass particles produced as a side product of nuclear fusion They hardly interact with matter so they can travel completely out of the Sun undisturbed Millions pass through you every second Detection of Neutrinos Difficult since they interact so weakly with matter Takes very large detectors Several have been built to detect different types of neutrinos from inside the Sun Pressure of the gas prevents collapse Pressure of escaping radiation also helps to prevent collapse If not enough pressure star will contract until pressure increases to balance gravity If too much luminosity and pressure gt Con rms fusion is occurring in center of Sun star Will expand until pressure drops Photosph3lt Cogth Pre Matter iinterior Structure of the Sun The pressure of a gas 1s due to motlon of gas atoms Pressure increases as you move Higher temperature faster speeds higher pressure deeper into the Sun Higher density more atoms higher pressure Must hOId up all the OVe aymg material Density and temperature increase Only in core is it hot and dense Compressing a gas increases pressure Dlslance Worn Center km l Heating a gas E 13 enough for nuclear fusion Fusion M m 7 needs very hot cond1tlons because 7 1 Increases pressure quot K the protons need to move fast a W w enough to overcome their h 3 electrostatic repulsion L All energy is generated in core w 5 Gquot quot km Copyright 2007 Pearson Prentice Hall Inc I Energy Escaping From the Sun Energy always ows from hot regions to cold regions So heat ows from the core to the outer layers and then into space Two major ways to transport energy out 7 Photons Radiation Transport 0 Deep interior relatively transparent to light so photons can carry the energy out 7 Currents of hot gas Convection 0 Outer parts are opaque to light so gas motions must move the energy out Cnpy igM mum pearsnn 3mm Hall Inn Question 0 In the Star Trek movie Generations The evil Dr Zorron launches a missile into a star The missile stops fusion inside the star so it blows up during a life and death battle between Zorron Kirk and Picard How long would they really need to be ghting before they would notice fusion had stopped in the star Random Walking Even in the relatively transparent interior of the Sun a photon only travels about 1 cm before it is absorbed A photon is absorbed and remitted billions of times before it wanders out of the Sun Reemitted in random directions each time It takes about 1 million years for a photon to work its way out The Main Sequence Revisited Like the Sun all stars arrange themselves to balance the force of gravity and their interior pressure 7 As mass increases gravity increases Pressure increases inside the star 0 Stars generate more energy and are more unity quotIn my luminous Stars are hotter and larger to let the energy out This equilibrium sequence of mass is the Main Sequence mm m sumac Iemperawm K mew swam Iasilllcs nn Key Concepts Lecture 29 Relativity Special Relativity General Relativity Falling into a Black Hole Speed of light 7 alileo tried to measure it by timing a light ash 7 Danish astronomer Olaus Roemer 1675 Timing moons of Jupiter Americans Michelson and Morley 1887 7 The speed oflight is the same no matter how fast the observer is moving EXPERIMENTAL The Problem with Light e 3 gifl lt3 I Space and Time Before Einstein 0 Galileo and Newton 7 Space and time are absolute I same grid independent of velocity 0 Velocities simply add together 7 Nolan sees the ball going 5040 feetsecond 7min iafm Einstein 5 Special Relativity 1905 Special relativity only applies for situations With no acceleration a 3 7 An inertial reference frame I t n 0 First Postulate 7 The physical laws 0fmlture are the same in every inertial reference frame 7 First stated by Poincare 18981904 Second Postulate 7 The speed of light is the same in ever inertial reference frame Einsteinius Special Relativ Velocities do not simply add 7 Light must appear to move at the same speed Space and time are relative 7 Distances between and times of events must be different as viewed by different moving observers 7min 100000000 ms mm T an 5000Wl70 mJ Nolan W lax 51k W W p13 a A parked train 7 Light moves up and down in the same amount of time for each observer 0 9 A movmg train 7 Light moves further as seen by the stationary ob server NI NF aceT1me 0 Time can be considered as a natural dimension like the 3 dimensions of space 7 the 43911 dimension The distance between events in spacetime will change depending on how fast you move 0 Space and time are Relative not absolute I Consequences of p39eclal Relanvny Time Dilation slowing of time 7 A clock will appear to move more slowly on a moving object 7 At the speed of light a clock will seem to stop ConSequences of Special Relativity The Twin Paradox Contraction of space 7 A moving object will appear shorter in its direction of 39 You y Off in a 59396 rOCket at 99 0f the motion speed of light to v1s1t a star 100 light years 7 Something moving at the speed of light would appear away Whlle your twm Stays on Earth to have zero length After a short stay of a few days you return from the star at the same speed What do you find when you return to the Earth answer discussed in class Hm SLHJMrCV sitting still Mass and Energy Mass and energy are the same things The Cosmic Speed Limit As an object moves faster its energy increases It behaves like it is more massive 7 It becomes harder to accelerate A little mass can be converted into a lot of energy At the speed of light its mass becomes infmite 7 It will require in nite force to accelerate it Energy can be converted to mass Nothing can go faster than the Emc2 speed of light The General Theory of Relativity General Theory of Relativity 1916 7 Einstein wanted to understand how gravity affects light 7 A new theory to explain gravity not as a force but rather as the curvature of spacetime he Principle of Equivalence 7 You can not tell the difference between acceleration and gravity 7 Acceleration by gravity is independent of the mass being accelerated Curved 2D Space l i A Precession of Mercury s orbit Gravitational redshift Einstein s Universe 0 Newton s notion of space 7 Is an absolute grid of coordinates Einstein s notion of space 7 Space describes the motion of objects with no forces on them 7 Space is altered by matter Tests of General Relativity Bending of star light by the Sun s mass m 39 7 May 29 1919 Solar eclipse m 7 Due to strong curvature of space near the Sun 7 Stronger the gravity the slower the clock 7 Tested by clocks in buildings amp space An Object Falling Into aBlack Hole Time appears to slow down for an object in a strong gravitational field At the event horizon time appears to stop as viewed from outside Light from the object falling in to the black hole gets redshifted further and further to longer wavelengths Photons emitted from the event horizon are infinitely stretched out infinite wavelength zero energy impossible to detect Black Holes What if remnant mass gt 3 Msun 7 Neutron pressure can not hold it up l I 7 Collapses even further if r 7 Escape velocity is greater than a speed of light 7 Density is so high even light cannot escape 0 light amp matter go in but they don t come out 7 Essentially completely cutoff from our universe Tidal Shredding Near Black Holes Strength of gravity depends on distance as lr2 If you were to approach a black hole feet first your feet would be pulled more strongly than your head Near a black hole this difference in force can be enough to stretch you out into something resembling spaghetti Black Holes Schwarzschild Radius is where the escape speed speed of light Event Horizon is a sphere of radius Schwarzschild radius 7 For 3an core this is 9km General Relativity predicts there is a singularity inside the event horizon 7 density and gmvity become in nite 7 Laws of physics break down need new physics Worm holes Newmatter Causality violated Energy conservation violated Formulae you Will be given this sheet in Midterm 1 Speed distancetime Key Concepts Lecture 13 Angular size 6 size distance The Moon Kepler s 3rd Law P2 a3 Newton s version of Kepler s 3rd P2 cx a3m1m2 Newton s 2nd Law F m a Structure Newton s Law of Gravity F cx m1 m2 r2 Density mass voume Volume of a sphere 43rrr3 Formation Surface area of sphere 4an Frequency f 1Period Speed of wave light frequency x wavelength c f A Exploring the Moon Moon rst observed through a telescope by Galileo in 1609 First orbited by Soviet spacecraft Luna 2 in 1959 Natural Satellite of Earth Only extraterrestrial body to be visited by humans 7 first manned landing July 20 1969 0 Apollo 11 0 Neil Armstrong amp Buzz Aldrin 1st to walk on the Moon Recent missions to the Moon Clementine 1994 Lunar Prospector 19981999 Basically no atmosphere on the Moon Discoveries from the Apollo Missions Structure is differentiated like arth s 7 low density rocky crust 60 km W thick 7 uniform amp thick mantle 71000 km 7 thick solid unlike Earth s more plastic mantle a few very weak Moonquakes 7 liquid center possible small iron core 7740 km thick Impact Craters WA 0 Nearly all features on the Moon are due to impacts 7 Probably no volcanoes Size of crater depends on 2 things 7 size of object bigger bigger 7 speed of object faster bigger Discoveries Ancient surface which preserves early history 7 heavily cratered areas are old 0 from dating of rock samples brought back to Earth 0 provides method to date surfaces of bodies in solar system using only their appearance Discoveries from the Apollo Missions Surface rocks are very old 7 yuungestrucksln rnana dark luw areas uldeitrucksln nrgnlands light enlnred areas A bllhnnyeaxsald Possible scenario for Moon formation Discoveries from the Apollo Missions 7 means Earth amp Moon formed from same material Moon is less dense than Earth 7 less lron e relatively small core for size compared to Earth Moon s formation nn Earth was hlt by a body llke Mars Discoveries from the Apollo Missions Lifeless e no fossils e no organic rnalenal The Moon is asymmetric l 7 Crust is inside D1 c0ver1e39s of Apollo lDrsCoverles of Apollo toWard Earth V 7 Maria mostly on Earth Moon melted early on and differentiated facing side 7 Low density material oated to surface amp formed highlands 7 44 46 billion years ago Very large impactsasteroid 7 created great basins The heavier side always points toward the Earth Cru39 upptm as km Mk Y738 M 7 filled W1th lava E 0 3239 billion years ago m 3 V NM 0 The only lunar vulcanism my WWI Moon is TidallyLocked to Earth l Water on the Moon 7 39 Clementine 0 Moon rotates about once per month so that it always 7 ew over Pole Moon Presents the same face to Earth39 7 at pole some craters are always in shadow 0 Initially it rotated faster but was slowed down by tides 7 mdar measurements detect ice in the raised by the Earth bottoms ofthese dark cmters The tides on the Earth raised by the Moon are also Emh radar found no evidence form slowing down the Earth s rotation the day is getting longer con icts with Clementine result However Lunar Prospector 1998 did con rm Clementine results But it is not clear exactly how much water there is or in w form it resides Key Concepts Lecture 15 Venus structure surface magnetic field atmosphere runaway greenhouse Use of radar transparency of atmospheres in radio Doppler effect Comparison of Terrestrial Planets Exploration of Venus Telescopic observation of Venus 7 Only see cloud layers 7 re ect 76 of incoming sunlight Visited by 20 spacecraft 7 Mariner 2 rst to visit in 1962 7 Venera 7 Soviet Space Cra rst to land on another planet 7 Venera 9 rst photographs of surface 7 Magellan detailed maps ofsurface from radar Venus Overview l Second planet from Sun Earth s sister planet 7 similar sizes masses densities cratering amp chemical compositions Atmo sphere Rotation amp Revolution Orbit of Venus around Sun 7 most circular orbit of all planets v 7 225 Earth days for 1 complete orbit Rotation of Venus 7 Retrograde in opposite direction of most other planets and most satellites in solar system 7 Very slow 243 Earth days for 1 complete rotation Earth Venus Structure of Venus Interior structure similar to Earth 7 similar mass size amp density Metallic core 7 somewhat lower density than Earth 7 somewhat smaller core than Earth Large rocky mantle Rocky crust Surface Varied Terrain 7 mountains 7 high plateaus 7 canyons 7 ridges 7 craters Overall relatively at compared to Earth 7 10 of Venus surface above 10 km V Magnetic Field 0 Very very weak magnetic eld Why 7 Venus rotates much more slowly 243 times than Earth 0 internal dynamo weaker weaker magnetic eld 10000 times weaker than Earth 0 Interaction with solar wind differs from Earth 7 solar wind runs right into upper atmosphere of Venus 7 carries off some of the atmosphere Radar to map surface Atmospheres are quite transparent in the radio wave band Sand measure rotation rates Uses Doppler effect Surface of Venus waves are Few craters Radar map compressed 1f 0 Several upland emitting object is plateaus moving towards us resembling and vice versa contlnents Lowland lava plains 0 Some volcanoes maybe active as revealed by variable gas emissions in atmosphere l J o o n a o a Surface of Venus Volcanoes Volcanoes occur in complex groups Shield volcanoes relatively at 0 often having a collapsed central volcanic crater at summit No small craters 7 small meteoroids burn up in Venus dense atrnosphere Craters come in bunches 7 large meteoroids that reach surface break up in atmosphere Atmo sphere of Venus WlndS 7 Upper atmosphere very Windy 7 speeds 7 350 krnhour 7 in direction of rotation 7 causes planet Wide circulatio 7 winds blow from equator to poles in large cyclones 39 100 500 km in diameter 39 vortices at polar caps Wind speed decreases lower in the atmosphere No Wind at surface Constituents 7 96 carbon dioxide 7 35 nitrogen 7 water sulfuric acid cloud hydrochloric acid Twat450 wrung 27w AnnaMuir a Temperature amp PreSsure Greenhouse Effect on Venus Temperature increases as 39 76 of sunlight re ected b clouds amp you get closer to the surface never reacges surface of mmmws 7 surface temperature 800 K g 7 WWW Venus Surface Pressure increases g Yet surface temperature F g as You get closer to the eXtremely hlgh 39 f t l in 7397 i 0 Surface tem erature hi h 7 surface 200 400 500 m p g 1m 6 CWW due to very strong I quotxx 7 90 atm 90 t1mes greater WWW greenhouse effect 39mrm ML 5 than Earth s surface NO oceans or life to Wquot W Pressure remove CO2 Questions about Venus The Terrestrial Planets Winadd hatnickel Why is its rotation retrograde Perhaps due WW am mime 333 W to giant impact mm quotmquot Why did Venus atmosphere evolve so v differently than the Earth s Probably Mercury Mars arth All terrestrial planets are differentiated enus because conditions never arose for large amounts of liquid water oceans too hot initially or not enough supplied by comets Larger planets take longer to cool and still have active mantles plate tectonics on Earth active volcanoes on Earth amp Venus and liquid cores The T rre t alPlsani l l Eunh Mars mummysingnnensmulplaneu mu Mm Ham 0 coal new In Lair u I 5w matMn 7 quotpuma Honel watlesilom pbnolv mak 5 e cm onus My info cl blawiu39imnIv r no inst Nu cruising vadr NM w hm co 922 N 152 N A m 02 2v 4o mmm i di hmnllem m 39 OK I m vacox 1w ow 7 aprum o lul IMx 47 71 mm minim rum M m on who O Volcanic activity creates secondary atmosphere Gravity holds atmosphere Light atoms escape most easily Higher temperatures allow heavier atoms to escape Water and life remove CO2 and life creates O2 lnluiov cold m mm mm my Small planets cool fastest and go through this planetary Lsix91 t39 11 faster l Key Concepts Lecture 22 Measuring the properties ofstars Th HertzsprungRussell HR Diagram L versus T The StefanBoltzmann Law flux emitted by a black body 0T4 Binary Stars used to measure stellar mass The Hertzprung Russell Diagram Hertzprung and Russell found 7 Stars did not occur with all possible combination of temperature and luminosity 7 Stars tended to group together 7 A large number of stars including the sun were found in a band they calE7 the Main Sequence This suggested that the observed properties of stars are interrelated Luminosity 5 5 m In an attempt to understand the physical nature of the stars astronomers tried to find correlations between their observed properties Temperature or Spectral Class 7 Luminosity The American Henry Norris Russell ca 1913 and the Danish engineer The Hertzprung Russell Diagram Ejnar Hertzsprung ca 1911 independently made a diagram sho wing these stellar properties Stars group themselves in various parts of the diagram Question Why would stars with the same temperature spectral class andor color have very different luminosities Luminosity and Sizes of Stars Luminosity Classes Stars with the same StefanBoltzman Law the energy emitted temperatures but every second by an object at temperature T different luminOSities is proportional to T4 and is proportional to fall into LuminOSitY the surface area of the object Classes Therefore total luminosity of stars 7 tiggi gjtsars are more L 4 7393 R2 0 T4v 7 White dwarfs are 39 temperature smallest StefanBoltzman constant 7 Supergiants the largest Radius of star The Sizes of Stars 0 If you know the luminosity ofa star and its temperature you can The find its size Sizes of 7 StefanBoltzman law L74ch2 0T4 Main 7 So we have S equence R2 L 4 313 0 T4 Stars Sizes of Stars Rise of MS is due to both temperature and size 7 Hot MS stars about 10X the size of Sun 7 Cold MS stars about llOX the size of Sun Super giants are about 1000X the size of the Sun White dwarfs are about 1100X the size of the Sun umuw 15m um 30000 20000 0 ii i r A I 000 5000 ympcmw Melvin Visual Binaries Binary systems for which both stars can be seen and period of orbit amp separation can be directly observed Visual binaries give us the best information about stellar masses Newton s adaptation of Kepler s 3rd Law m1m2gtP2 a3 w pm 1345 9 3 l 51 Binary Stars Binary stars Two stars orbiting each other due to mutual gravitational attraction About half of stars we see in the sky are actually binary stars but they are too close to separate with our eyes If we can measure the orbit it allows direct measurement of masses of stars by using Newton s adaptation of Kepler s 3rd Law just like measuring the mass of Jupiter by measuring the orbit of its moons 39lt39 I Some binaly staIs are too far from us for us to see the separate staJs I Using spectm We can detect the presence of tWo stars 7 Presence of spectral features rewect tr the u server VcA7tt characteristic oftwo ditfererrt types of stars 7 A periodic Doppler shi ing of spectral unes blue sht ed s m rrmtmrt I Bmaly systems Where one star For Main Sequence passes 111 front ofthe other Th m b gm fth stars the lmmnoslty I eappare 11 nesso e 1mm 01 system changes peIi dically due to 15 re 6 0 6 mass the eclipses ofthe stars I From light curves 7 Details oforbits e Shapes and sizes of stars 7 Relative temperatures of stars mquot a 0 as I 2 s m an MtLuLmun The Reason for the Main Sequence The main sequence is a sequence of stellar mass 7 Low mass stars appear cool r umul 7 High mass stars are hot The relation between radius temperature and mass is determined by the balance between gravity and the pressure that prevents the star from collapsing or blowing itself apart mummy a Key Concepts Lecture 11 Earth s Atmosphere and Greenhouse Effect Intro to LightEectroMagnetic Radiation Earth s Oceans Temperature set by energy in energy out 7 Energy In From sunlight 50 reaches the ground 7 Energy Out Infrared light from heated surface Without Atmosphere Taverage 18C With Atmosphere Taverage 15C 7 Atmosphere is transparent to optical sunlight 7 Water and Carbon Dioxide is opaque to infrared from surface energy is trapped and heats 30933 gsnoH 119919 aql Atmospheric Composition Protects the surface Atmosphere 7 78 Nitrogen 7 21 Oxygen 7 1 Argon 003 Carbon dioxide Water 7 Blocks ultraviolet radiation from Sun 7 Blocks cosmic rays and radiation 7 Blocks small impacts Regulates Surface Temperature 7 Clouds re ect sunlight 7 Atmosphere traps and hold heat 7 Atmospheric circulation moderates temperatures l J o o Light Electra Magnetic Radiation One way we can uavelangth think of light is as a wave of electric and lz mpli m magnetic fields J a f The vieciric rim Rom an isoiaied po sltwe charge 1i ie wmic HAM vim a ii isoiaiea negative change i J o o o n a o a Light ElectroMagnetie Radiation 39 At each point in space the eld amplitude oscillates as e Wave oes b the Period P of the Wave number of periods in one second is the frequency f1P eg 50 oscillations per second is a frequency of 50 Hertz In one period the Wave travels one Wavelength 7 the speed of the Wave is cdistancetime MP 7 f Light fromEverything B body Radiation All objects with a temperature above absolute 0 273C 459F 0K emit light the light Waves carry energy Temperature is a measure of how quickly the atoms in an object are moving and vibrating Hotter objects emit more light energy because the motions ofthe electrons are more violent larger amplitude ofWaves in electric field Hotter objects emit shorter Wavelength light because the frequency of oscillation of electrons is higher The time of one oscillation is Speed of light is constant in urn c constant so high frequency light has a short Wavelength The ElectroMagneti e Spectrum Electromagnetic waves of different wavelengths Visible light is only a very small part of the whole EM spectrum m w W am new m w Earth 5 temperature is about 300K Room temperature objects ie T300K emit light that peaks in the infrared with wavelengths 10 microns This is about 20 times longer than visible light and is not visible to our eyes Temperature set by energy in ener out 7 Energy 1n 7 From sun hght 7 50 reaches the ground 7 Energy Out 7 Infraredlight from heated surface Without Atmosphere Tavemge18C with Atmosphere Taverage715c 7 Atmosphere is transparent to optical sunhght 7 Water and Carbon Dinxideis opaque to infrared from surface 7 energy is trapped andheats The Primordial Atmosphere The original atmosphere hydrogen and helium 7 These are the most common elements in the universe 7 Came from formation of Earth Atmosphere was lost 7 Light atoms move faster than heavy 7 Hydrogen and Helium have low mass 7 Their velocity is above escape velocity 19933 9snoH Heals 9111 Question so Since the industrial revolution no man has been burning more trees and fossil fuel This has caused the amount ofCO2 to increase in the atmosphere wumolm rm 5 g 5 E What effect would you expect this to have on temperatures on Earth Atm0spherlc ESCape Propenies of a gas 7 behaves like a group ofhard balls moving and colliding 7 S tide cmknnthete Light gas panicles move faster 7 When they collide with more massive particles they recoil at higher speeds The gravity of a planet holds the gas in 7 More massive p1anets can hold 1ighter gasses IUer O f a Evolution of the Atmosphere Second atmosphere from outgassmg earmee meurseeneurmrnem CHLM om Remevmg the carbon drexrde eeeaaaeme aaaee aee e arenaa m ae mere germane mnlymmm 1s x Fermauer esz and co2 umwhxnmwmkwmm mama Magmaeaeaemaeeaa can 4 km Helpsregulaleandmudaale amt Impunanl fur evaluan er atmnsphere Must have lxqmdvala39 fur Me Cun39ams much erme Me unEanh Very mue pnmordAal oxygen 7 Almnstm axygeanxlhanyurs age 2 afumnsphzn ms 01 7 6m mlan yzars age ereeearaereaae Ongm of oxygen 7 Bmlagwalum y mdd 5b11mn yzars age 7 Plan canvm cog mm 01 aamaapeareea e Deadbmmassxstnppdmthz Earthmd member Water En bererraeved by subdumun Question If the Earth had no water and therefore life had never occurred what would the Earth s atmosphere be like If you were trying to locate a planet with life on it what atmospheric constituents would you look for Key Concepts Lecture 16 Jovian Planets What are the Jovian Planets Background Discovery Basic properties rotation orbits seasons 4 Giant Planets in the outer solar system beyond Mars 7 Jupiter Known to Internal Structure Atmosphere clouds winds storms 7 Saturn the ancients 7 Uranus Discovered relatlvely recently Magnetic field 7 Neptune with telescopes and Newton s Laws Space Mlssmns T0 Ollter Planets Characteristics of Jovian Planets Much larger and more massive than terrestrial planets They are not solid gaseous All have rings All have many satellites Voyager Characteristics of Jovian Planets Questions Which of the above planets experience seasons and why What would the seasons be like Rotation amp Orbits Fast rotation ie quite short days Orbital periods obey Kepler s 3rd Law P2a3 Jupiter 7 aXis of rotation tilted by 3 no seasons Saturn 7 aXis tilted by 27 has seasons Neptune 7 aXis tilted by 29 has seasons 7 seasonal changes slower than Saturn s Uranus mzomgtmm 7 aXis tilted by 98 strange seasons 0 H and He are light and can Seasons on Uranus Orbit takes 84 years 1 A Slt PN Amount of sunlight varies dramatically amp depends on 5 5m 39 locatlon 51 5 31quot 7 poles see sun for 42 years then darkness for next 42 years What caused this extreme tilt 7 Perhaps a collision With a large body during formation Why do they have H and He Jam escape more easily than heavier atoms Ea SE d 39uamp smum Neptune nr Sp Spaadkmr s gvm tn np mama N The gas giants are massive so they have high escape velocities They are far from the Sun so they are cold and the atoms in their atmosphere move quite slowly mums so new 400 405 me 300 mu 7 r gt L 20 1 Ion 20a 00 son em Temperature Composition amp Structure of J ovians Mostly Hydrogen amp Helium They have low densities At most they have only small rocky cores Internal Heat Sources Primordial Heat from gravitational contraction associated With formation 7 Larger planets are heated more strongly during formation by collapse of material and rapid initial differentiation Also it is more dif cult for this heat to escape from a larger planet takes longer to cool down 0 Continued generation of heat by gradual differentiation eg condensation of He in Saturn Radioactive decay relatively unimportant because heavy elements are smaller fraction of total mass Effect of internal heat raises the temperature of interior amp atmosphere to higher values than expected from only Sun s heating Wmds amp Clrculanon 39 Fatures ubsa ved are due m nrculauun ufduuds at summers lumen planelsare stmtamrs r hmmmxlcxrculmmn pmms pnn ehn mm 39 Nu suhd surface 7 155 mm faxurmlh nn mm m Ins enzng 7 mu m shims r cmhnve mm mm mew mm mm Inlanal hat suurce muses va uml cunvemun curmuts Clouds amp AcmoSth Atmnspha39e mumy Hydrugm at Helxum Cluuds gve Jumans may appmnce 7 plum Sam pp dank affmun Amman NH 39lnwzx cksrammamnm hydms dzNH51Drdark yzllnws ampbmwns mum 39anms 15 feamnless 7 sub atmnsphzxe Jupiter Movie Winds amp Circulation Alternating light amp dark bands parallel to equator stretch around planet Semipermanent features 7 shift in intensity and position from year to year Eastwest wind patterns 7 do not appear to change at all even over decades The Great Red Spot on Jupiter A giant cyclone that has been going for centuries 30000 km long Changes in size over time l H Storms Storms local disturbances in the regular atmospheric circulation patterns Seen on Jupiter Neptune Saturn 7 Great Red Spot Jupiter long lived gt300 years 7 Great Dark Spot Neptune probably shorter lifetime 7 Seasonal storms on Saturn The Great Dark Spot on Neptune Dark Spot seen in Voyager images 1989 7 similar to Jupiter Great Red Spot same shape same latitude 7 10000 km long Dark Spot not seen in Hubble Space Telescope images 1994 7 faded or disappeared 7 storms may form amp dissipate more quickly on Neptune Storms on Satum Magnetic Fields Large storms are rarer Jovians have strong magnetic fields Magnetic fields generated in the same manner as on Earth 7 metallic liquid regions plus rotation of planet causes dynamo 7 Jupiter amp Saturn may have liquid metallic hydrogen cores or near cores Connected With seasons 7 every 30 years outbreak of spots are seen in the equatorial regions Storms resemble turbulent cloud structures 7 Uranus amp Neptune have liquid metallic hydrogen mantles Very large 10 times size of Earth Hubble Space Telescope image 1990 Magnetic Field omnl o magnetic OXIS 3 34 10 Fkldll um SLOW amour m in an as a Key Concepts Lecture 6 Constellations Ancient Cosmologies Early Greek Astronomy and the Physics ofAristotIe Con ellaxtrons There are patterns of stars which have not changed over human history Looking up at the sky people imagined pictures and grouped these stars together into constellations This helps us to remember the patterns of the stars Just like pictures in clouds the stars do not trace the pictures in detail Many are associated with stories and legends Constellatlons Constellations reflect the cultures and times of the people who created them 7 The oldest constellations used by astronomers today originated in about 3000BC in Mesopotamia I These were hunters dogs bears etc 7 Southern hemisphere constellations used by astronomers originated in the 17th century by sailors I These were ships telescopes compasses etc Today if we were naming constellations we may see TVs CD players cars space ships etc Or10n the Hunter Orion is a prominent winter constellation Located near the Celestial Equator so it can been seen from either hemisphere Located near the Milky Way vnumm mumsy o Onon Greek Mythology 7 Orion son ofPoseidon was agreat fearless hunter 7 His arrogance angered the goddess Hera who sent a scorpion to kill him 7 The moon god Artemis placed him in the sky far away from Scorpio Jewish the Biblical Samson Arab Al Jabbar the giant China Hunter and warrior Tsan Brazilian A Cayman cousin of the gator Egypt The God Osiris Ursa Major amp Minor Ursa Major is the most prominent northern circumpolar constellation Ursa Major contains the Big Dipper asterism Ursa Minor contains the Little Dipper asterism Ursa Minor Tm mmwmw Big Dipper V Major 7 39 Two stars in the front end of the Big Dipper point to Polaris GrecoRoman Mythology 7 Callisto amp Zeus were lovers amp had a son Arcas Hera Zeus wife was angry and turned Callisto into a bear Years later Arcas was hunting amp was about to kill his mother so Zeus stepped in amp threw them both into the sky Hera still wanted revenge so she made the pair continually circle the sky never being able to refresh themselves in the RiverOcean that encircle the earth Ancient world pictures of the cosm 7 geocentric earth centered wood cut by 7 nite had boundary French typically a shell of stars astronomer bounded the universe F1 ammarion Ancient cosmologies paid little 39 circa 1880 attention to celestial motions even if celestial cycles were carefully observed Nut Egyptian goddess of sky arched over Geb god of earth The Babylonians were among the rst people known to have kept astronomical records kept continuous written records of observations on clay observations used for making calendars amp predicting stars attached to a shell far beyond earth Sun entered through a Gate at edge of Universe Babylonian tablet recording astronomical information circa 550 BC 7 Sky is like a at plate support by 4 mountains 7 Sun is canied across the sky in a boat from east to west At night Sun is canied back to the east through 7 Earth is a circular disk surrounded by the ocean 7 great mountain in center of world 7 Sun goes around mountain once a day 7 sky is a round dome surrounding earth 7 Sun travels in a big tilted circle l 1 Early Greeks Ancient Greek astronomers were the first to attempt to explain the workings of the heavens in a careful systematic way using naked eye observations and models Greeks enjoyed philosophy which to them meant the attempt to understand all things in nature They used their highly developed mathematical skills geometry amp trigonometry amp logic to make remarkable discoveries about their universe Aristotle 384322 BC showed by proof that the earth was spherical He observed that the Earth s shadow is curved during a lunar eclipse 7 The shapes that the Moon itself shows are of every kind straight gibbous and concave but in eclipses the outline is always curved and since it is the interposition of the Earth that makes the eclipse the form of this line will be caused by the form of the Earth s surface which is therefore spherical Aristotle s treatise On the Heavens Painting of Aristotle by Rembrandt respect to the horizon Flat Earth 2 Aristotle learned from travelers that the height of the Pole star above the horizon varies as you travel from North to South 39 Going North Polaris gets higher with respect to the horizon 39 Going South Polaris gets lower with 39 Go far enough south Polaris no longer 5 visible 2 gtEarth must be spherical Aristotle also reasoned that the Earth was spherical by watching ships leave port and sail off towards the horizon What would you observed about a ship sailing away from you if you lived on a Flat Earth Spherical Earth Key Concepts Lecture 20 Solar System FormationLight Formation of the Solar System the Nebular Hypothesis Light wavelike behavior Light particlelike behavior Light Interaction with matter Kirchof f s Laws Orrgrn of Solar System Planets orbit the Sun in same direction counterclockwise viewed from above the Earth s north pole and in nearly the same plane Most planets and the Sun also rotate in roughly this same direction although planets can be tilted occasionally by large angles Most moons orbit around their parent planet in this same direction Solar system is differentiated 7 Terrestrial planets high densities small to moderate atmospheres slow rotation 0 to few moons 7 Jovians low densities thick atmospheres fast rotation many moons Asteroids are very old 7 primitive unevolved material common age of oldest solar system material 46 billion years Comets primitive icy fragments from Oort Cloud or Kuiper Belt Origin of Solar Sstem Observations of the different members of the solar system place constraints on theories of its formation 7 motions 7 chemical composition 7 age Origin of theiSolar System Nebular Hypothesis due to Kant amp Laplace 39 Slowly rotating interstellar cloud of gas amp dust 39 Gravitational contraction 7 disk attens 7 conservation of angular momentum 39 Sun forms at center of nebula 7 retains original composition inu want MI Movie ofsolar system formation Origin ofthe Solar System Planets fm39m m dust near center 645k uf gas and ufnebula O gin ofthe Solar Syste A mmmm g m Gravny Cullen39s planzteamals m farm Pramplmels 7 L229 11an anucmd ms Wm med mwmg aresstemstfqmliugt See star formation section later in course l Thellmportance of Li ht system in our lifetime The easiest Way We can learn about distant objects is by studying the light they emit 39 Using information in their light We can measure compositions temperatures istances masses and ages of astronomical objects 39 As light travels at a finite speed by looking further and further away We look back further and further into the past 39 We can not hope to visit objects outside the solar TIL Visible light isjust onei form of electromagnetic radiation Light o en behaves like a wav e r Diffraction r Interference 4 gt V All EM radiation is composed of two Waves 7 Ah e1e trre field and am rte e eld 7 The elds are at 90 degrees to each other 7 It needs no medrurr to be transmrtted through r e rt can travel through a vacuum 7 Energy rs camedby thewave Properties of Waves A wave is described by four properties 7 The wavelength A units of length 7 The amplitude of the wave The ElectroMagnetic Spectrum Waves of different lengths and frequencies make up the EM spectrum 7 The speed of the wave 0 units of speed lengthtime 7 The frequency of the wave f units of ltime Three of these properties are interrelated WIVI h CIOI a wlve l W If i I 7 Wavelengths shorter than the amp 7 7 speed blue are called the ultraviolet The visible colors are one small part of the EM spectrum 7 Wavelengths longer than red are called infrared EM spectrum extends from radio to gamma rays The Earth s atmosphere only transmits certain frequencies Q Q C L w Al shaves L 5 B xke A Pamela u have A mm M39th 15 called am Fm suggesdele Planck my mm xmk m qm mmm mm hxxmzmlhwmim swtml Phnmelzcmc mm mm 1905 Emma WWMWW w mmmmxmmmm a Q mmmm mm m a mi mm bmamk ww ymhsquot mmammaammmrm sumo mmummmmzmemu a up M W The Interaction The Interaction of Light with Matter 39 K iffjft mg Nh znscmnpuseda mums mm muummww Light typicallymtzmts wnhmamrby man wAth m electmns Amnrd mums The Stair Case Analogy You can think of the levels of an atom as being like a ight of E O stairs To step up to a higher level 5 0 requires enough energy to lift 0 you one or more stairs When you come back down the 2E o starrs you grve up the energy you f got by going up the stairs 39 Spectra of Atoms Iwrogun f 4 Sodium Helium Ni on Mum Finger Printing the Elements 0 Each type of atom ie different elements like Hydrogen Helium Carbon Oxygen etc has a unique con guration of electrons Each type of atom has a unique set of possible energy levels 0 Each type of atom emits and absorbs photons with a unique pattern of energ1es Kirchhoff s Laws waxw Gustav Kirchoff derived three laws to explain how matter and light interact He noted that three types of spectra arise under different conditions 7 Continuous spectra 7 Emission line spectra 7 Absorption line spectra manly mum um 3 won 50006000706091 The Generation of Light All dense matter with a temperature above absolute zero emits light because of vibrating electric charges electrons The spectrum is the amount intensity of light at different wavelengths The peak of the spectrum depends on the temperature v tuxmm hotter temperature h leads to peak at shorter wavelengths if This is called a Blackbady Radiation a continuous spectrum We can use Wien s law to nd the temperatures of distant bodies we can never visit by measuring the wavelength or the frequency at which the spectrum peaks Wren s Law Wien s law tells you at what wavelength the blackbody spectrum peaks 7 Hotter objects emit light that peaks at shorter wavelengths higher energies 7 Colder objects emit light that peaks at longer wavelengths lower energies Vl2DDDK a 500 2000 moo 1500 Mn m a Kirchhoff S 1st Law A hot and opaque medium emits a continuous spectrum because the atoms are very close to each other which smears out the energy levels This is the blackbody spectrum quot 7 Hot Solid A hot transparent low density gas produces a spectrum of bright emission lines The number and colors of the lines depend on which elements are present Because the atoms are quite far apart the energies of the photons are not smeared out The emission lines are due to Heated Gas electrons moving to lower energy states l 3rd Law Ifa continuous spectrum passe through a tmnsparent gas at a lower temperature the cooler gas will cause the appearance ofdark absorption lines whose colors and number will depend on the elements present in the gas This is because particular energies are absorbed by the cool gas electrons are raised to higher energy levels Then when the electrons fall down and new photons emitted these photons can go in any direction most do not go through the slit 3 C ooheri as Hot Solid 1 Class website httpWWW a fro HFI quot 39 39 100 nd 39 html 2 Discussion sections Tuesday period 4 10401130am Bryant 3 Wednesday period 8 3pm350prn Bryant 7 Thursday period 5 1145am1235pm Bryant 3 office hr Thursday period 7 140pm 240pm Bryant 3 3 Homework 1 due Thur 11th Sept and Quiz 1 due Thur 4th Sept on website 4 Read pages 1 34 of Chaisson amp McNIillan then continue reading from p34 onwards gt Chapter 2 Open Friday Nights If classes in session Weather permitting call 3925294 after 7PM to Check Hours 830 7 1000 pm Location South of Union amp West ofEng Science For extra credit bring form from class web site Key Concepts Lecture 4 Solar Eclipses Angular Size Lunar Eclipses 1 What is special about the Tropics ie between 235degrees and 235 degrees latitude Flm quanel sunsex anh Fol Mmmgm quotEarm s mmnon Sumo Thin warm If the Sun sets at 6pm when does a rst quarter Moon rise Ec lips s A solar echpse occurs when the Moon moves between the Sun A lunar echp se occurs when the Eath moves b etvveer the the Moon moves through the In ancreru cultures ecupses were bad omens The Moon Moves Over the Face othe Sun The Sun is Nearly Covered The Diamond Ring Total Solar Eclipse Angular ize rme andMOTOH The Sun and Moon have Ver different physical sizes 7 Radius ofSun is 7x105 km 7 Radius ofMoon is 17103 km 7 So the Sun is 400 times bigger than the Moon How can they appear to be nearly the same size during an eclipse Answer the Moon and Sun coincidentally have nearly the same angular size Angular size of an object depends on two things 7 The physical size of the object 7 The distance to the object Angular size measured in mdians Ph izltgiiglze y or we write it as 9 Why does an annular eclipse look different 139 ocllpu a III um min b A total solar eclipse can seen from only a small region on the Earth 7 in order to see a total eclipse the Moon must appear to cover the entire disk of the Sun 7 you observe this when you are in the inner shadow umbra of the Moon Partial solar eclipses are seen over a larger area 7 to see a partial eclipse only part of the Sun needs to be covered by the Moon 7 you observe this when you are in the Moon s outer shadow penumbra The Moon s shadow moves over the Earth during a solar eclipse S 7 a 3 4 Hquot y I hitpsunean1gsfcnasagovec11pseechpsehtml Aug 2151 2017 chpses occur at new Moon They do not occur every month 7 The on s orbit is lteds degrees to the ecliptic ey occuI when the Moon cmsses the ecliptic when it is new Moon 7 A partial total or annular eclipse can occur some place on Eart between 3 and 5 times each yeat 7 A total may occuIO tos times a year Talmpo r11 III moon The Lunar Eclipse Earth s mm m We see a total lunar eclipse when the Moon moves through the Earth s inner shadow umbra We see a partial lunar eclipse when the Moon moves through the Earth s outer shadow penumbra Lunar eclipses are Visible anywhere on the nighttime side of the Earth A Lunar Eclipse Why is the Moon s surface still Visible during a total lunar eclipse Lunar eclipses occur at FULL Moon PHASE Lunar eclipses do not occur every month because the Moon s orbital plane is tilted with respect to the ecliptic 7 a total lunar eclipse occurs when the Moon crosses the ecliptic at full Moon 7 since the Earth s shadow is much bigger than the Moon total lunar eclipses occur more often than solar eclipses Lunar eclipses occur 25 times per year Key Concepts Lecture 21 Measuring the properties ofstars Temperature T from peak of spectrum and spectral lines Composition from spectral lines Apparent brightness or energy flux F from telescope detectors Distance 1 from parallax Luminosity L 4 1 cl2 F Classifying the Spectra of Stars Late in the 19th century photography became good enough to record the spectrum of a star Annie Jump Cannon 18631941 7 Harvard college observatory 7 Found that the spectra of stars fell into natural categories 7 She took spectra of nearly 400000 stars Spectrum of an Object Light dispensed into umponenl colours ie a Spectrum Lighuourm I eg 5m or lamp Slil Prism Dispersion of light through a prism l Intensity mm mm H r The Spectral Classes of Stars OBAFGKM Stars given a letter class based on Which absorption lines are present mo 0 We now know this corresponds to T if 39 different temperatures from hot to m cold the sequence is OBAFGKM 0 391 jiA 7 0 stars hottest M stars coolest 7 Each letter class divided into 10 l I I subclasses from 0 to 9 39 Iquot r am 139 7 within each letter class the spectra are q l 0 similar arranged so the classes merge 7 r k 39139 lIil mm smoothly into each other l 0 B9 is more similar to A0 than B0 0 Sun is a G2 star with T5800K vilmmomg n 7 ummm cm Spectral type measure of temperature e Sur ace temperatureK Blue 1100021000 White Stellar Abundances Each element and ion has a unique pattern of electron energy levels and thus absorption lines From spectra we can identify elements that are in the stars Helium was first identi ed in the Sun and only later found on Earth Cecilia PayneGaposhkin in her PhD thesis in 1925 determined that stars were made up mostly of hydrogen amp helium contrary to notions of the time that stars were made up of the same elements found on the Earth 7 74 H oftotal mass 7 24 He oftotal mass 7 2 everything else of total mass Ionization of Atoms What is ionization 7 Process by which an atom loses electrons 7 For a given element a minimum energy is needed to break an electron loose a y 7 Energy can come from photons or collisions k I between atoms 0 Temperature controls the ionization of elements 7 Atoms move faster when hotter Faster collisions can lead to more ionization 7 Thus the absorption lines will change depending on the temperature e g a line due to the presence of neutral H will disappear at 7 temperatures where the H is all ionized Parallax to nd distance 0 As the Earth orbits the Sun nearby stars shift their apparent angular position ie Right Ascension Declination on celestial sphere in relation to more distant stars The apparent shift in a star s position depends only on its distance from the Earth 7 More distant stars have smaller parallax angle shifts p l d JMW IAUr lAU JUN W mum A sum ln Jammy umquot ln My Parallax Parallax angle decreases for more distance stars 1 degree 60 arcminutes 3600 arcseconds prarallax angle is 1 arcsecond d1 parsec 326 light years Earth lAU d 2 L Sun N p 1 2 1 Recall angular size real sizedistance So we have p lAU d Question What happens to the apparent brightness of the head lights of a car approaching you along a highway Question If the star has a parallax angle of 13 arcsecond how far away is it If we can measure angular positions to 001 arcsecond accuracy how far away can we measure parallax distance The Apparent Brightness or Flux of Objects The Luminosity L of an object is how much energy it emits every second The Apparent Brightness or Flux Fofan object is how bright it appears to be ie how much energy we receive from it every second The Apparent Brightness or Flux depends on 7 The Luminosity of the object 7 The Distance to the object Flux at distance r Star wnh FiLMR luminu quot P surface urea of sphere 412 The Inverse Square Law of Light Question 0 The apparent brightness or FluX of objects decreases as the square of its distance 5am amuum nl mm W was mmugn scums Two stars A B have the same apparent brightness on the sky Star A has twice the parallax of the other Which is more luminous and by how much A unum ammml a pa 525 Each 1 din Imoug ugm 1mm 4 w mm on Waning me muse more KIM Key Concepts Lecture 37 The Search for Planets and Life Transit Technique The Habitable Zone Estimates from Drake Equation SETI and Fermi s Paradox Depth of Transit Depends on Relative Sizes of Star and Planet Transit search technique measures the size of the planet if we already know the size of the star Transit Search A planet passes in front of its star We see a small dip in the brightness of the star If we know the size of the star we can then measure the size of the planet First Planetary Transit Detected in year 1999 Star is called HD209458 Radius of planet is 13 times Jupiter s radius Mass of planet from radial velocity technique is 063 times Jupiter s mass Why is the planet so big Probably because it is so close to its star is strongly heated and so is puffed up The Drake Equation l lNumber QfElane ES SuftableforLi39fe TheHaEitableZone N R f N f f f L Need liquid water to sf wp sfl lbr ll ts t r I Ni number of technological crvrhzatrons now present in the Mrlky Way Temperature Rsf rate of star formation over lifetime ofthe Galaxy 7 10 Range f p fraction of stars With planetary systems gt005 7 l 01 7 only planets Ns average number of planets suitablefor hfe certain distances r flb fraction ofhabrtable planets Where life anses from their Star can I Vl MM Wk MM f1 fraction of lrfebearrng planets Where intellrgence evolves maintain d water mm 1 I f5 fraction of intelligentlife planets that develop technology mum syntax Lt average life time ofa technological civilization 7 alternathe heat 39 7 39 quot 1 m sources 0 tidal forces 0 volcanoes Fraction Life l I Fraction with IntelligentLife l Intelligent life arose on Earth despite many 39 Life on Earth arose very rapidly catastrophic mass extinctrons flb N 1 7 once life forms intelligence is inevitable fu N 1 Anthropic Principle Anthropic Principle Earth must have 7 We would only exist in a solar system Where intelligent life for us to ask this question life arose 7 Earth is not representative 7 fi1 ltltlt 1 7 Earth need not be representative 7 flb ltltlt 1 7 Even on Earth rt took several brllron years for intelligent life to develop Technological Civilizations The Drake Equation Advanced civilizations developed many Ntc Rsf pr Ns flb f fts Lt places Ol l Earth Rsf rate of star formation over life time of galaxy 10 per year 7 chances are that any one such pr fraction of stars With planetary systems 1 01 civilization would have developed NS Average number ofplanets suitable for life 1 01 communication technology flb fraction ofhabitable planets Where life arises 1 0001 T fi1 fraction oflife bearing planets Where intelligence evolves 1 01 How long does this communication phase last i Ntc number of technological civilizations present in the Milky Way 7 On Earth 100 years so far Nto 1010 10394 civilizations fts fraction of intelligent life planets that develop technology 1 01 Lt average life time ofa technological civilization 109 100 years How CloSe is our Nearest Neighbor SETI For our extremely optimistic value of 1010 communicative civilizations 7 average distance to nearest neighbor 6 light years For less optimistic values of 1000 civilizations this is still very optimistic 7 average distance to nearest neighbor 7 1000 ly Judie Fusta39m Cuntaitquot i Attempt to detect radio signals from extra terrestrial civilizations Began in 1960s Lost federal funding in early 1990s Now privately funded eg Paul Allen of Microsoft r I How many agar systems have heard us We have been sending radio signals into space for about 70 years These have now traveled 70 light years in every direction On average there is 1 star in every 4x4x4 ly3 64 ly3 The volume of the radio sphere is 43 m3 14x1061y3 So there are about 22000 stars in this volume that could have detected our radioTV Search for I EarthlikesPlanets www jpl nasa gov Problem 7 planets faint 7 stars bright Solution 7 Very precise optics 7 Telescopes in Space 7 Optical and infrared wavelengths 4 light years 4 l Fermiquots Paradox If there are a multitude of advanced extraterrestrial civilizations in our Galaxy the Milky Way then where are they Why haven t we seen any traces of intelligent extraterrestrial life such as probes spacecraft or transmissions eg an intelligent civilization should be able to spread out and colonize the entire Galaxy in several to tens of million years Perhaps they are already here studying us discretely Zoo hypothesis Perhaps we are the only ones formation and survival of intelligent life is dif cult Perhaps communication and interstellar travel are much more dif cult than we imagine Searching for Earthlike Planets Our solar system as it would be seen by TPF from a distance of 10 parsecs Earth By the year 2020 we hope Search for Life Oxygen in planetary atmosphere is a signature of biological life processes Oxygen can be detected from the spectrum at midinfrared wavelengths via OZONE xntonuty B 9 10111213141516 Wavelength nu Question You encounter a UFO and make contact with ET You are only allowed to ask one question What would that question be UF Os Einstein Special Relativity 7 nothing can travel faster than speed of light 7 severely limits interstellar travel and visitation 7 Probably would involve large scale colonization expeditions that would take thousands of years Nearest Neighbors 7 6 very very optimistic to several thousand still optimistic light years away But we do not really know 0 Most UFO sightings are explainable as astronomical objects such as Venus l Further Reading and Info 0 Astronomy News www spacecom www space ightnowcom Life in the Universe As Life Everywhere by David Darling Rare Earth by Ward amp Brownlee tronomy at UF 1 Class website pg 7 g frgigwrg r7 7 2 Discussion sections Tu ay penud4 1U Arm mam Bryant 3 Wednesday pde 8 3pm snpm Bryant 7 Thursday pde 5114 de 35pm Bryant 3 uf cehr Thursday pa39md7 14mm 7 zAUpm Bryant 3 ur znz 3 Quiz 1 not for credit on class website deadline Friday 1 lam 4 Homework 1 is on class website and is due 6pm Thur 11th Sept 5 Exam dates midterml 25th Sept midterm2 30th Oct nal 9th Dec 6 Read pages 134 of Chaisson amp McMillan then continue reading from p34 onwards gt Chapter 2 Key Concepts Lecture 7 Aristarchus and the relative distances to Moon and Sun Parallax Eratosthenes and the size of the Earth Precession Aristotle Hipparchus Ptolemy a geocentric model of solar system Observing Report Campus Observatory Open Friday Nights 7 Ifclasses 1n sess10n E h L 39 n Puna 7 Weather permlttlng g Reitz Union call 3925294 after 7PM to check E Museum Rd Hours o 83071000pm 39 E Location South ofUnion amp Physws 39 E West OfEng science Obse to rEn In eerlng Smence See class website for Q ry instructions about observing I Lecture 7 Overview Ancient Greeks amp Aristotelian Physics 7 How did the early Greeks model the universe 7 What are the key physical ideals of Aristotelian physics Ptolemy How did Ptolemy apply Aristotle s physics to model the cosmos Copernicus What were the main differences between his model and those of earlier Greeks Tycho Brahe What were his major contributions to Astronomy Estimated relative sizes of the Moon amp Earth Estimated distance to Moon relative to Earth s diam Estimated distance to Sun relative to EartnMoon distance timed duration of lunar eclipses compared the time it takes the Moon to enter the Earth s shadow with the time it takes the Moon 0 to cross the Earth s shadow measured angular size of Moon amp compared this to the estimate of the Moon s size relative to Earth s diameter Assumed Moon s orbit was circular amp uniform Measured angle between SunEarth Moon at lst quarter estimated this to be 87 deg so 013 deg Then EarthMoon distance is about 3360 x 231 x EarthSun distance But it was difficult to measure these angles Aristarchus thought the as 20 times mher away than the Moon but it is really 400 times irther a Parallax i B A If Earth moves around Sun then we should see parallax I ie the displacement of I foreground stars with respect star to background stars Parallax could not be seen by early Greek astronomers one argument against the Sun centered model eg by Aristotle A B In fact parallax effects are earth 0 earth real but very small as the JanJ Mll stars are very far away 5 wetlle mama Aristarchus of Samos 310 230 BC Estimated size of Sun 7 from total Solar Eclipse using relationship between angular size physical size and distance Angular size rmasnedrnnnans Physical Size Distance Aristarchus estimated all these uan 2 Aristarchus found that the Sun was much bigger amp much farther away than the Moon 2 He therefore concluded that the Sun not the Earth was at the center of the Universe Erato sthenes c 200 BC Eratosthenes estimated the Earth s diameter and thereby took the relative measurements of Aristarchus and placed them on an absolute scale On the summer solstice at noon 7 the Sun was directly overhead in the city of Syene Egypt 7 but in Alexandria Egypt the Sun was displaced from the vertical 7 Using a gnomon amp basic trigonometry he determined that the angle from the vertical was 770 7 this angle the angle between Syene amp Alexandria as seen from the Earth s center 7 Alexandria was 5000 stadia from Syene and so the circumference of the Earth was 7250000 stadia 7 But what is a stadium length Modem estimates 1572 1667 m Erected an observatory on Rhodes amp built instruments to measure as accurately as possible the direction of objects in sk y compiled catalog of stellar coordinates 850 entries discovered precession direction ofEarth s axis ofrotation slowly changes moving in a circle every 26000 years re ned Aristarchus technique to measure Moon s size amp distance 7 295 earth diameters actual distance 30 earth diameters determined length of year to within 6 minutes carefully observed motions of Moon Sun amp planets predicted lunar eclipses to within 1 hour 1st to deal with the problem ofparallax for solar eclipses amp predicted the paths of totality for solar eclipses Developed a geometrical geocentric model of the universe HipparChus C 150 BC Precession of Earth s Rotation Axis gt was Drumms Earth s axis wobbles um1 because it is not quite perfectly spherical and the Moon and Sun s gravity act on these imperfections Effect is weak so period of wobble is long 26000 years Our rotation axis ie the north celestial pole does not always point at Polaris Modeling the Cosmos Observations to Ex lain Scienti c Models Conception of a physical model to explain the workings of nature is a creative act of science Ke 7 Motion of Sun East to West in about 12 hours from sunrise to sunset Models apply known laws of nature to explain observatlons West to East along ecliptic 7 l0 per day Key aSPeCtS Of a seien c mOdel Small variation in speed along the ecliptic Variation of length of day amp height of Sun with season 7 Motion of Moon East to West in about 12 hours 25 minutes from moonrise to moonset West to East within 50 of ecliptic Sidereal relative to stars amp synodic relative to Sun eriods gt models explain what is seen gt models predict observations accurately gt simplify your understanding of nature Validity of models is tested by checking how well predictions t the best amp newest observations Scienti c models are not necessarily static but can evolve when new amp better observations become available Modelmg the Cosmos Ke Observations to Ex lain 7 Motion of Stars I East to West in N 12 hours from star rise to star set I star rise is N 4 minutes earlier each day I cirqunpolar stars I stars in xed position relative to one another I precession I yearly motion relative to Sun Aristotle amp Geocentric Model Geocentric Earth at center motionless Universe finite in size Motion of Sun Moon Planets amp Stars was 7 circular 7 uniform constant rate of motion Model consisted of 56 spheres Did not fit observations well First to incorporate physical ideas or concepts of motion Modelmg the Cosmos Key Observations to Explain 7 Motion of Planets East to West in 7 12 hours from rising to setting interval varies depending on rate of planet s motion with respect to stars I West to East within 70 of ecliptic Average speed varies along ecliptic 7 fastest for Mercury 7 slowest for Saturn Retrograde motion from East to West at a time specific for each planet Aristotle s Physics I Cosmos was d i ided into two realms 7 Incorruptible Universe Heavens 7 Corruptible Universe Near the Earth 7 Incorruptible Universe I Eternal unchangeable region in the heavens I Natqu Motions No force required Natqu motion of heavenly spheres was rotation Aristotle Cowuptible U niverse aregion r change hear the Earth 0 made up of four basic elements39 EarthWater ii Fire Natural Motions 7 Earthy mate rial moved toward center of cosmos 7 Fire moved to highest heights 7 Air below Fire 7 Water between Earth amp Air Forced Motions for e ustbe pushed in order to move Aristotle s Physics Aristotle believed Earth was stationary and at the center of the universe because 7 Natuml motion of earthy material is t Ward the c nter of the cosmos 7 We do not feel the Earth moving 7 If Earth rotated then objects thrown upward would not drop bac to their point of departure as they are observed to do 7 If Earth moved about the Sun then one should observe stella parallax yet this was not observed Question I In Aristotelian physics the Earth was stationary and at the center of the universe Imagine you lived at the time of Aristotle What observations or evidence could you offer to support the idea of a stationary Earth Hipparchus Added geometrical devices to the basic Geocentric model of Aristotle to explain the motions of the planets 7 Eccentric Epicycle Deferent Eccentric 7 a circle along which the Sun or a planet traveled around the Earth with the Earth displaced from the center 7 explained the variable motion of the Sun amp Planets through the ecliptic Hipparchus Epicycle amp Deferent 7 Deferent a large circle either centered on Earth or offset from Earth eccentric 7 Epicycle smaller circle centered on the circumference of the deferent Ptolemy 125 AD Designed a complete geometrical model of the universe that accurately predicted planetary motions with errors within 5 Most of the geometric devices and basic foundations of his model did not originate with him but were based on the models of the early Greeks such as Aristotle amp Hipparchus Wrote the Almggest Greatest 7 included the original works amp models of Ptolemy 7 Combination of Epicycle amp Deferent explained retrograde motion 7 included a compilation of past works of Greeks 4quot r especially Hipparchus quot a 7 13 volumes Well do I know thatI am mortal a creature of one day Planets fixed to the epicycle Planets moved around eplcyCIC WhICh 1n tum But ifmy mind follows the Winding paths ofthe stars moved around the deferent Then my feet no longer rest on Earth but standing by Zeus himselfI take my ll of ambrosia the divine dish I I I I i l I I o a Ptolemy s Model Earth was spherical amp at center ofcosmos GEOCENT RIC Cosmos is nite in size Ptolemy s Model Equant 7 point inside a circle not at the center from which motion along the circumference of the circle would appear to be uniform Earth has no motions Sun Moon Planets exhibit uniform circular motions 7 lay opposite the circle s center from the eccentric the Earth 7 mmghysical totally geometrical device that broke the fundamental assumption that planetary motion had to be uniform along circles 7 natural motions no forces Used devices of eccentrics epicycles amp deferents to explain the observed nonuniform motions of the Sun and planets along the ecliptic amp retrograde motion With the introduction of the equant celestial motions no iii longer had to be uniform around the centers of circles Ptolemy used equant so that his model would t observations Introduced eg uant to explain the variations in retrograde motions Copernicus 14731543 i Copernicus Model Developed a Heliocentiic Sun centered model of the I r H V 39 COPemiCUS WOfkea 0 His new HSHOCSHtf cosmos model for 20 years 7 Sun was placed at center of cosmos 7 Earth no longer static but revolved around Sun once a year amp rotated on axis once a day Why Ptolemy s geocentric model lasted for centuries mainly because it accurately predicted celestial motions so there was little reason to discard it Copernicus studied the works of Aristotle Pythagoras His work was published in De revolutionibus in the year ofhis death De revolutionibus took a er the Almagest in outline and basic intention to explain planetary motions An offshoot of Plato s philosophy asserted that Sun was godhead of all knowledge Copernicus objected to equant based on aesthetics equant not faithful to ideal ofuniforrn motion makes models too complex Even though it took 20 years to develop this model did not predict celestial motions any better than Ptolemy s geocentric mode The daily motion of the heavens relative to the horizon results from the Earth s motion on its axis 7 aesthetic appeal since only 1 sphere is rotating not many 7 however he did not account for the objection that if the Earth rotated objects should be ung from the surface The apparent motion of the Sun relative to the stars results from the annual revolution of the Earth around the Sun Cosmos nite in size Assumed no forces for heavenly motions 7 physics of Aristotle Assumed uniform circular motions 7 done for aesthetics followed Aristotle The planets retrograde motion occur from the motion of e Earth relative to the other planets 7 retrograde explained as a natqu result of the planet s revolutions about Sun what we observe is an illusion All heavenly spheres revolve around the Sun amp the Sun is at the center ofthe cosmos 7 chosen based on aesthetics and simplicity The distance from the Earth to the sphere of stars is much greater than the distance from the Earth to the Sun 7 accounts for lack of observed stellar pamllax Retrograde Motion Explained When the Earth passes any of the outer planets retrograde motion occurs Copernican Model Copernicus eliminated epicycles to explain retrograde motion Eliminated equant kept uniform circular motion Needed to account for variations in planetary motion so he was forced to add many smaller circles Complete model more complicated than Ptolemy s larger total number of circles Violated Aristotelian physics amp did not offer new physical ideas to support his model Didn t predict motions any better than Ptolemy s model Comparison of Ptolemaic amp Copernican Models m mquot Elm Observation Ptolemy Copernicus Motion of entire Motion of All heavenly Re ection of heavens from E to W Spheres E to W rotation of earth Arbltrary as long as w to E Distances of Planets angular relationships Set by observations Annual Motion of Rotation of sun s Re ection of annual are cone sun W to E through sphere W to E in a year revolution of the zodiac earth about the sun Cause of Planetary Natural motion of Same as Ptolemy Nonuniform motion Circular path of sun motlons celestlal Spheres no of sun throu h eccentric with uniform Same as Ptolemy orces zodiac speed Retograde motion Variation in retrograde motions Relative motions of Epicycles amp deferents planets including earth d s Equant eccentrics Small epicycles eccentrics Accuracy of prediction Error typically 5 degrees or less Same as Ptolemy lo 5 e V39 gt1quot Class website 7 Admin Discussion sections Tuesday period4 10 4011 30am Bryant 3 Wednesday period 8 3pm3 50pm Bryant7 Thursday period 511 45am 12 35pm Bryant3 of ce hr Thursday period 7 1 40pm 2 40pm Bryant 302 Homework 7 due 6pm Saturday 29th Nov will appear on class website soon Telescope observing project see class website due Tuesday 25th Nov Half credit for NonObservatory Report for 2 objects Use name tags in class Reading Intro Chapters 113 not 134 14 15 16 17 Final Exam Tuesday 9th December in class About 12 ofthe questions will be on material since midterm 2 The Distribution of Galaxies Galaxies tend to group together on many scales Gravity is the glue that tries to bind all galaxies together Groups The Local Group The group of galaxies of which the Milky Way is a part 3 million LY across 30 total members Three large spirals 7 M31 Andromeda M33 amp Milky Way Total mass 5x1012 Msun Key Concepts Lecture 33 Towards Cosmology The Distribution of Galaxies towards a large scale view of the cosmos Why is the sky dark Implications for the cosmos The Expanding Universe The Age of the Universe since the Big Bang Clusters of Galaxies Some galaxies are found in dense groups of 100 to 10000 galaxies Few spiral galaxies in clusters Typical sizes 10 million LY across Galaxy collisions are frequent note galaxies can be changed in a collision but the existing stars are not affected stars do not collide TheRmh CluSLErAbell 2218 522 The Masses of Clusters Clusters are bound together by gra y masurethe 7 Usmg eD urbnalvelunues erme axles 7 We En thespply NEWLun39s versmn er Kepler39slawlu nd39he mass Typically span 100 Manon LY 7 Theyt xmllyhave K xmuremassthanmn Typmny comm 1015 M be seenm e Stars 5 Mostofspacexs empty of galaxxes Other emdenee for high mass 7 1n nnuK X y ermmng gas is buundm dug 7 clusters ll unly 5 ufvulume 7 vauauunal lensmg ufbankguund galaxies Thethh yavnauunal masses er clusters er galaxies CDmpalEd tn the mass seen m stars and gas lsmure emaenee fur DARK MATTER Walls and Filaments The Cosmological Principle 0 Galaxy groups tend to form larger walls and laments 100 s of 0 If you look at larger amp larger chunks of the universe it Will eventually look Homogeneous and Isotropic MLY long 0 Simply stated this means that there is no special or preferred place in The great wall the universe of galaxies T 500 Million LY long 7 All parts of the universe will 7 15 Million LY thick behave the same 7 2X1016 Msun 7 This must be true if we ever wish to understand the universe as a whole The laments tend to be separated by VOidS This appears to be true on the largest scales 7100Mpc With few galaxies Movie of Large Scale Galaxy Distribution Cosmology the Wh 01 e Universe How Big How Old What is its Future Olber s Paradox why is the night sky dark 7 If the Universe is in nite in size and age and uniformly lled With stars on average then every line of sight should intersect a star producing a Bright Sky I Like looking through a forest u o o n a o a 1 Possible slutiions l l The Rec ding Gala 7 621011 is very meound 1912 Vesto Slipher of Lowell Universe has a finite size Observatory 7 all the galaxies he observed were moving away 7 some as fast 1800 kmsec 0 19291953 Edwin Hubble amp Milton Universe has a finite age light from most Humason Stars hasnat reaChed us Edgar Allan P09 7 More distant galaxies were moving away faster 7 The speed increases with the distance Universe has an infinite size but few or no stars far away It turns out that the 3rd one of these solutions is the main reason the sky is dark at night In every direction the Galaxies are receding from us I 39 theUniyerse is EXPAEDLNG eding l l w 397 Jigij Hubble amp Humason 1931 Does this mean we are in a special place the center of the Universe Japan v 7 7 1 NO There is no center of 1 expansion Every galaxy sees the N same thing more distant A i i galaxies recede more quickly Hubble s 1929 data lw39 5 Analogies the expanding raisin m N mum in mm my pirxn cake 3D dots on surface of a Velocity is proportional to the distance v at d balloon 2D knots in a rubber 7 70 kmsNlpc H0 d band 1D v Constant x d l o L What Hubble s Law is Not The umverse 5 Lot expandmg mto space Space xtselfig expandmg Hubbly 5 Law Explained Expanmh lmpnemere wag a egth g All ofspace 5 Expanding All pomts m space get spread further a an Ifthe universe 5 expandmg we can follow the expansion backmtoume theumversemust t P The rate at whmh pomts move apams proportional to than separation vlud m 1 Class website in r 2 Discussion sections Tuesday period 410 4011 30am Bryantii Wednesday period 8 3pm3 50pm Bryant 7 Thursday period 511 45am12 35pm Bryant 3 of ce hr Thursday period 71 40pm 2 40pm Bryant3 or 302 Telescope observing project see class website Quiz 1 not for credit see your results on class website Homework 1 is on class website and is due 6pm Thur 11th Sept Homework 2 will be on class website later today and is due 6pm Thur 18th Sept 7 Exam dates midterml 25th Sept midterm2 30th Oct nal 9th Dec 8 Reading Intro Chapters 1 2124 41 5 999 Kepler s 3rd Law Applies to Any Object Orbiting the Sun 0 P2 k a3 with k constant P period of orbit and a average distance of object from Sun 0 Earth has Pl year a 1 AU so using these units kl and we can write 132a3 Examples lfa planet has a 4 AU then it must have period P 8 years 8X8 64 4X4X4 This formula applies to any orbit around the Sun from circular to very eccentric e g comets Key Concepts Lecture 9 Newton Newton s Laws of Motion More on Kepler s Laws Newton s Law of Universal Gravitation Newton 1642 1727 Only child posthumous son of an illiterate yeoman 7 born prematurely sickly as child 7 raised by maternal grandmother 7 as a child he built clocks amp sundials 7 practical joker Trinity College Cambridge University at 18 7 studied mathematics amp astrology 7 encouraged to study physics by Barrow University closed in 1665 due to plague 7 Invented calculus studied gravity optics Barrow resigns amp gives Newton his post at Cambridge Describing Motion Laws ofMotion Position Law szunngm rAbadyanesLannmahanata 39 1 cansuntvdac R 7 ate of change ofposmon speedamp dArecuon 39 Acceleration net gums ram iRate ofchange ofvelomty R y mgammghl m myquot motion isl39uslm namla Intfar a body of blilg a is Laws ofMotlon Examples ofthe Second Law Law a FarceLaw lt a m m uf change m an object39s may due m an Wham 5 m m same recumaskpmpmhamlta u r c2 andmvexsdypmpmhamlta Jen39s mass Friction iHockey puck on me vs on a street Impact ofa hat on a baseball aThebanmpans aforce Lethe ball and sands n H mgmthe opposite direction the ab Ta have accelexauanthzxe mustbe afmce Farce amp accelexahan alwayswmk mLhe same aman Gwen the m e farce a v2 ab m accelerates m are slowly mm a less Question abuund my head m a male Laws ofMotion LawllLReacthaw 45m ball Ansel13mg 4mm accelexaungwhnlxs MW 4 mngmmbmkmwmmm mmmn Question Yuu push scan andltmuves but yuu du nut appear m muve iwmdan39twumwexf39hexexsanappame andequal farce pumg mum m equ bulappasxtefmce Fumes always acclx m pm afar mbecrentedm xsalauanr needallea WD bu agmn each v1th Kgmmyxs afmcextmust m bemenbmes Dzmmslxmm 2nd mum quewlan39s Laws 2m sz Force mm x accelzn m r m s thnwubudms mmhrms eyfeelmoyposm mdmccm m4 and mshen h meshzcmzrdnmsbmwudunmzykxm me Why7 mam mummy yul m 3914 mm mm mm was only A momma quotwe mm In nwe an m k m mm m dud Newton Flgures Out GraV1ty He unlfled the force Whlch rnakes an apple dr p from 39 and the force whleh makes the moon orblt the earth Newton s Law of Unlvers a1 GraV1tat10n 39Fome is plopox onal to the masses 7 ravity causes all nhiects tn attract nne annther He lntultlvely gured out that the force of gravl e 1 ts depends on only three 7 Thetwomasses f rSmallex mass asrnaner tome lsorauta lt Foree is invexsely plopox onal to the distance between the objects ie that thlngs the obj ets objects glves a stronger e rnore rnasslve attraetlve force he dlstanee b en th objects movlng objects further apartweakens the force Thl s true on slze seales from alaboratory desk to ensure aparta weakex tome s l groups ofstars and galaxles The Inverse Square Law Orbits and Gravity Force weakens like the square of the 31223 distance ifyou double the distance the force changes by a factor of 12x2 14 force whlch keeps the planets from spaee e Beeause the Sun ls rnueh rnore rnasslve then the planets the Sun eontrols the rnotlon of the planets Gravlty always pulls the planettowardt e un t warm 5 PvHHVsul r awan s to keep the planet movlng ln a stralght 11113 The balance etween gravlty andlnerualeads to the stable orblt b We V of a planet W 3 Sun e Moonis rnueh eloser to the Earth than the Sun The inverse square law ofgravity means thatthe Moon s orbit is controlled by the rnass ofthe Eanh rather than the s e force the Moon feels from the Earthis stronger than that it feels from the Sun The Shapes of Orbits T115143 Brahmas utbltdeyerds arms veinch Fxpmdmlhrm as nice aroawty A budywltlrlz Hillarerth wimllywl A m Search m AbudymtlrlzhrglPeerdmdzrwlm ywm mam as Encem39gzwtymdm mzhlgex Kepler s 2 1 Law Kepler s 3 71 Law Planets with larger average As a planet moves toward the Sun the force di stances from me Sun M of gravity causes it to accelerate along its longer orbits and it moves fa er 7 Slnce the gavltatlonal As a planet moves away from the Sun the me who 5 1955 they move force of gravity acts along its orbit and more slowly along Lhelr orblts ows it down I 39 r The orblts are larger Newton s Adaptation of Kepler s 3rd Law Newton S Cosmology Gravity holds the solar system 0 Newton applied his laws of motion and gravity to derive a together 7 The Sun is the most massive object so its gravity 7 a rd 2 3 mod1 edvers1on ofKepler s 3 law WluChWaS P k a do i tes 1 e sol Syste 7 The law of Universal Gravitation naturally produces elliptical orbits Kepler s 1 law 7 The law of Universal Gravitation naturally produces Kepler s 2quotquot1 and 3rd laws Beyond the solar system the universe of stars must be in nite or it would collapse 0 Here K is a new constant This equation can also be written as Motal P2 K a3 In the solar system the mass of the Sun is so large that Mom lIs nlIplanet is almost exactly equal to Msun This law allows the determination of masses for distant WWW Complexity to Simplicity Complexity to Simplicity 0 For centuries people had tried to understand the unique motions of 4 39 Laws Of PhySics MOtion and GraVitation descrlbed the m0t1011 the planets of the planets amp much much more 1 They were Gods that had special power over our lives 7 The planets obey the same laws of motion and gravity as any object on the earth 2 They were mystical bodies moving in a complex clock work universe with or m the universe I Orbits epjcycles equants amp deferents 7 The planets are composed of the same types of matter as is the earth Not composed ofthe same maten39al as the Bank 7 The same laws of motion amp gravitation can explain a wide range of phenomena I Not covered by the same laws of nature as the earth 39 The orbits of planets 3 They were special objects moving under the control of three laws of 39 Tides planetary motion I How to build a bridge or tall building amp land men on the moon Key Concepts Lecture 32 Galaxies Galaxy Types Spirals Ellipticals Irregulars 39 The Classi cation of Galaxies Galaxies can be classified by how they appear on the sky Spiral Density Waves 7 How attened the spheroid is 7 How prominent the disk and spiral arms are 7 Ifthere is a bar 0 Hubble devised what he thought may be an evolutionary sequence Mergers of Galaxies and Galaxy Evolution Active Galaxies more evidence for supermassive black holes Elliptical Galaxie Only a smooth spheroidal 39 component Spiral Galaxies Have disk with two or more arms 7 Bulge is old and red 7 Disk has gas and star formation Hubble sequence Sa Sb Sc 39 39 7 size ofnuclear bulge vs disk 0 No prominent disk MS7 E0 tightness ofspiral arms Composed of old reddish stars 39 Sa ghtestpattemamplalge bulge I Sc open pattern amp smallest bulge SO or lenticular Hubble class subdivides them E0 circular E7 most elongated Little dust gas or ongoing star formation 7 Have disk but no arms M84 SO M83 classed as SBb NGC 4565 Edge on Sb What are Spiral Arms Spiral arms are regions with a higher density of gas dust amp stars The rotation speed in these galaxies is approximately constant with radius So Why do the arms not get more tightl a wound up W A r the spiral arms are denim Spiral Arms The Spiral of the Milky Way 0 Hydrogen atoms emit 9quot 0 Spiral arms are density waves radlo WaVeS Wlth a 7 As the gas and stars orbit the galaxy they change their speed as Wavelength of about 210m they approach and leave the wave so they spend more time in the Due to Change 1 allgnment 0f arm becoming bunched up PIOtOH amp Electron 7 This is similar to What happens to cars in a traf c jam Egzz gves P355 thmugh duSt Because the gas densities are higher in spiral arms they tend to be traced by star formation Can be used to map the spiral arms of our galaxy regions 7 Use Doppler shi and rotation of Galaxy to determine the distance Irregular Galaxies Dwarf Galaxies NO Splral Structure 0 The smallest galaxies are or nuclear bulge dwarf ellipticals 39 Dominated by OB No current star formation Stars amp regions of ionized gas created by the hot OB stars About the same number of stars in a globular cluster Tend to be found near larger galaxies The most common type of galaxy Large Magellanic Cloud Galaxies are relatively big compared to the space between them Interacting Galaxies and so can sometimes undergo interactions Gm and m m m gmups Ovemme dynzrmcal fncnun causesthem m x a 11 r m u merge lnteracuuns uncur pnmanly thuugh gavlty e m addmm m mergers mal Fumes mnelse tar bus eme galames apart 7 Nu starsadually culhde Mam effects e Starburstsquot Bubs summaled e Canpmduc talsandshellsufsvars Milky Way and Andromeda C0111s10n The Antennae Antennae with HST IStar clusters in formation Bands of dust and gas The Cart Wheel Galaxy A Splash encounter The Masses of Galaxies e s at a i are supported against gravity by their 0 Use Doppler shi to measure orbital velocities Use Newton s adaptation of Kepler s thin lawt masses ofgalaxies Typical mass 10mm Mquotn forlarge galaxies 0 measure the 5 Galaxy Evolution I Interactions are one major driver of the evolution ofgalaxies I The merger of tWo gasrich spiral galaxies can ult in an elliptical galaxy with relatively little gas The gas Was turned into stars during the merger in a Starburst The Masses of Galaxies I Spiral disks tend to have at or rising rotation curves 7 Thus as in the Milky Way mass continues to increase as you move outward expected from the stars amp g I More missing massl Further evidence ru Dark Matter 7 The total amount of mass is ab outhx greater than that as asap minim Guunumuwcl Active Galaxies Active Galaxies 7 Pawer d camwtemxgysame mmlclnls G Ame seem Nudms cmmnslrnm 7 Vembie lummasny changes wvusevenl yzaxs 7 5m ampbmademisganlmespctn 7 Radm emssmn and jets 7 X7uys gammamys va emissmn The black hole paradigm Supermasslvehule 1n6 7 my Mm Release gamtatmnal energy as matter falls in Rutaung matta39 urgamzes mm a disk Hutmnerpms ufdisk emu bnghdym x7eey7epeeei Rutaung BH acts like pamele acceleratur m pruduce radm Jets Radio Galaxies acmam kma efeeme galaxy Radm telescupes fuund abuut H mm ufgalaxies had vary bright radm Radm Jets ufcharged pamcles ungnate m nucleus uf galaxy Ream lubes embeup m 17m Mp acruss The galaxyisusually an elliptical and u enmteracnng urdisturhed Evidence for Black Holes Rapid variability requires small size m Vayef cientreleaseofmergy 7 1U ufmass energy kmez Dynamics indicate large nonstellar mass e meme


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