New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here


by: Mylene Russel


Marketplace > Oregon State University > Physics 2 > PH 104 > DESCRIPTIVE ASTRONOMY
Mylene Russel
GPA 4.0


Almost Ready


These notes were just uploaded, and will be ready to view shortly.

Purchase these notes here, or revisit this page.

Either way, we'll remind you when they're ready :)

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Class Notes
25 ?




Popular in Course

Popular in Physics 2

This 99 page Class Notes was uploaded by Mylene Russel on Monday October 19, 2015. The Class Notes belongs to PH 104 at Oregon State University taught by Staff in Fall. Since its upload, it has received 21 views. For similar materials see /class/224531/ph-104-oregon-state-university in Physics 2 at Oregon State University.

Similar to PH 104 at OSU




Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 10/19/15
t This Set of Slides This set of slides covers the fate of the universe where it is we are heading Unit 82 51w m E par sion Forever Or Collapse mime Hx mumMinimum The fate of the universe is If the total energy is positive ultimately controlled by its 0r 2 the eXPanSion total amount of energy commues forever 7 Energy of expansion positive Ifthe tOtal energy is negative 7 Gravitational energy that can the expansion Will halt and the Slow the expansion negative un1verse Wlll contract and eventually collapse Density ofthe Universe If we can measure the density of the universe we can predict how much gravitational energy the l l l l o universe has and therefore 1 Whether it will collapse or E l g l keep expanding TD 1 M Z w The critical density of the 5 9 3W 1 l universe pc is the dens1ty at 1 Big Crunch which the total energy of the l i I 39 universe is zero 7 r lSGyr r lOGyr View Today SGyr lOGyr lSGyr gravitational energy balances me the kinetic energy of QM ppC Where p is the measured density of the universe expansion 2 If QM gt 1 the universe will recollapse 3H If QM lt l the universe will expand forever pc 872G If QM l the universe is exactly at the critical dens1ty 1 C 1 Density ofthe Universe continued Q based only on visible matter QVM is much less than 1 Astronomers believe the contribution of dark matter makes QM very nearly or greater than 1 Most likely 1 a at universe BUT if Q 1 or greater then the estimated age of the universe becomes less than the age ofthe distant galaXies This doesn t make sense Size of the Uh werse l i i i i i i i l i 1 77 Universe Frcscm m i i i i 1 Supernova Type Ia Findings Recession Velacny a l Gyr lO Gyr 5 Gyr Eday 5C1 lClel 7523yr Time New attention was given to the universe expansion We can measure the recession velocity of distant galaxies using Type Ia supernovae as standard candles Disiunce 4 Result It appears that the expansion rate when the universe was half its current size was less than it is today This shows that the expansion rate is increasing with time 7 Dark Energy y r mm m a a a win Noncrdmury dark mulleriwlMPse 267 Ordinary but nonlumlnnvs mullar dead slurs gusl 3 SW Rodrohon Ordm 0005 visible mailer ms and gas 05 Dark energy may provide the In order for dark energy to solution t0 this mystery make this occur it must make Dark energy remains constant up around 70 of all of the everywhere energy in the universe AS graVity weakens With As with dark matter dark distance the outward push of energy is not yet detectabla dark energy would accelerate the expansion If So So What The future universe will not recollapse in a Big Crunch Galaxies will recede at everincreasing speeds faster than the speed of light Light from them will redshift until they fade out of sight The visible universe will get increasingly more sparse The stars of the visible galaXies will run out of fuel and fade into darkness Close galaXies will merge and split Matter that doesn t disappear into black holes will be cold and dark After long enough decays into radiation only Even black holes may evaporate into radiation only An incredibly vast dark nothingness This Set of Slides This set of slides deals with Dark Matter and the Expansion of the Universe Units covered 78 79 Like a planetary system galaxies rotate as nonsolid disks Because they ARE nonsolid disks Rotation curve for galaxy is not the same as for a solar system It s at But it shouldn t be The outer stars are rotating too rapidly based on Visible matter Within their orbits wquot m lkmxl t S A ic Rotation Curves The 1chle Compam In canned for reproduelmn or msplzy aw M Missing Mass We can calculate the mass of the Milky Way by measuring the orbital velocities of dwarf galaxies in orbit around our galaxy We can also count the number of stars in the galaxy and estimate the galactic mass The two numbers do not agree By a factor of 10 Rotation curves do not show the expected decrease in stars orbital velocities with distance there must be much more mass present in our galaxy By a factor of 10 Astronomers cannot find or see this mass Rotation velocity gt Astronomers attribute this difference to dark matter Distance from center of galaxy gt We call the missing mass dark matter 4 4 flat rotation Gunes r mpmduuiqn mm 417 2 NGC 1085 539 39 P NGC 7033 UGC12810 Orbital speed kms 1M NGC 7606 quotquotquotquot MKEC 3200 Distance From nucleus ikpc Dark matter is not unique to the Milky Way Rotation speed kmsec l O 20 3O Radius kpc 99 percent of the stars in a galaxy are Within 20 kpc of the center Gas extends far out into the disk but is not very massive Galaxies are now thought to be embedded in a darkmatter halo that surrounds the entire galaxy Unfortunately dark matter cannot be detected directly Matter Distribution 0 Halo can be misleading not a ring 0 Density of Visible matter stars dust in a galaxy is highest in the center but falls off rapidly with distance from center 0 Density of dark matter is highest in center of galaxy but falls off gradually and even eXists between galaXies Once again dark matter seems to be the solution 7 10 times as much mass as the Visible matter 39j lusters of Galaxies Missing mass is also a problem in clusters of galaxies 7 Not enough Visible mass to hold the clusters together by gravitation and to keep hot gas in their Vicinity 7 Cluster mass must be 100 times greater than the combined stars 7 Gases previously unseen accounts for a tenth l Gravitational Lensing To Mm ma Mcnmwrmlli am am In Pemmxm rc uncd l39nrra roducnonorm lav mags of quasar A One InIervemna galaxy looks like u ls here bends Quasar a 1 Another image of the quasar looks like u is here Dark matter warps space just like ordinary matter does General Relativity The path of light rays bends in the presence of mass A galaxy or other massive object can bend and distort the light from objects located behind it producing multiple images This is called gravitational lensing Ga laictiJGrQ lusteli Gravitational Lens m e c mm Amount of matter needed to provided lens effect is 10 times the amount of matter visible at any wavelength 90 of the universe is not detectable to us l W39Inat IS Dark Matter 77 4 Unknown All known matter interacts with SOlVlE wavelength of electromagnetic radiation Perhaps small cold planetsized bodies Cold dead white dwarfs Nonrotating neutron stars Black holes MACHOs Massive Compact Halo Objects Not enough of such things have been detected to make up the quantity of dark matter needed Perhaps neutrinolike particles except massive WIMPs Weakly Interacting Massive Particles So far Dark Matter is entirely unlike any matter we are familiar with uff ofthe Universe Matter of the Asible Universe percentage hydrogen helium oxygen carbon everything else element uff ofthe Universe percentage dark matter Matter of the Universe hydrogen helium stuff everything else The Recession of Galaxies npyHgJuAD iiuucummmlmmpmym lnc penummmqmrm fnrreylmducunnm dnplm lOMp 2o Mp 30 Mpc 40 Mp Milky A len s Way A B guluxyv C 17 I t I as I L U L L c As seen 700 v r 0 700 1400 gt 2ioo gt moo a From luvs Milky Way 2100 mm 2100 2100 2100 2800 Asseen r r 700 70 7700 71400 72100 72100 from alien39s 2800 lt 2100 4 1Aoo 700 v 7 0 700 WY kms Recall from Hubble s Law that the farther away a galaxy is the faster it is receding from the Milky Way 7 V H x d This gives the appearance that the Milky Way is at the center of the Universe and all galaxies are moving away from us perhaps due to some large explosion The Big Bang However Hubble s Law can be applied to any observer in any galaxy No matter where you are an expanding Universe will give this appearance This lack of a preferred location in the Universe is calle t e cosmological prin ciple An Expanding Universe Towngmi he carme Compamu Inc Pmmwnn mm formpmdumou mauplav x l x x l gt4 l l g l i r The expansion of the Universe is not 0 Rather the speed of light is constant and like the explosion of a bomb sending it 1s space that was moving relative to the fragments in all directions through PhOton space 0 If each galaxy is like a button attached to Th t H d 39 a rubber band an ant walking along the 6 space 1 56 Is eXpan mg39 band as it is stretched will appear to have we can deteCt photons that appear to a velocity slower than it really does The have moved at different speeds buttons galaxies are xed relative to through space space but space itself is moving CnpyngH o m comm rmmnm m l mmmnn mqmma m mpmduc mn nrdwplay alcmv m D 2quot 2 l c 39 l 0 v I f 30cm Ramquot ma am bdon my Ramquot mend dough alter Hwyg Another Analogy The expansion of the universe and the increasing distance between galaxies is similar to the increase in distance between raisins in a rising loaf of raisin rea The raisins are xed relative to the dough but the dough expands increasing the space between them Problem with these analogies 7 loaves and rubber bands have edges 7 We have seen no edge to the Universe there are an equal number of galaxies in every direction 7 Also galaxies can move relative to space as gravity can accelerate one galaxy toward another faster than space expands The Meaning of Redshift Cupylighl a he Mcherili Campquot on nrdispla AS light anes traVel through iiig im illisl lilll n Space they are Stretched by increasing iheir wavelength expansion This increases the wave s wavelength making it appear lower frequency An objects redshift z is M xi Long wavelength implies cool JShoriwavelengih implies hot Z This is equivalent to Here AX is the change in wavelength and 7 is the original wavelength of the photon Change in average distance between galaxies Average distance between galaxies nqunghl a m mamanu smupmm Inc pmmsm icqmmdfnrre39lrodumo n in mm Therefore Bu according to the Hubble law V Therefore I 4 i a39H H r The Age of the Universe Thanks to the Hubble Law we can estimate the age of the universe At some point in the distant past matter in the universe must have been densely packed From this point the universe would have expanded at some high speed to become today s universe Assuming a constant expansion over time we find that the age of the universe is around 14 billion years This Set of Slides 0 This set of slides deals with curvature of space and the edge of the universe Also deals with the early universe a summary 0 Units covered 80 and 81 Olber s Paradox Over very large distances galaxies in the universe are more or less uniformly distributed We say the universe is homogeneous If there are galaxies in every direction however why do we not have a fullylit sky We should see a star in any direction we look 7 This is called Olber s Paradox If there is an edge to the universe we should be able to see our way out of the woods Olber s Paradox In a large enough universe every line of sight evenluolly encouniers o slur wilhin u go oxy I Q Ls 5 1 o ASqution 3 1quot In a sense there is an edge to the universe an edge in time or an edge to our vision quot Light travels at a nite though very fast speed The size of the visible universe is the distance light can travel Within the age of the universe Galaxies could eXist at greater distances but light from them has not reached us yet The edge is called the mmgno m mowmncmnmh v mmimlwmndfzrlwmduci Ga lesexxslbeybndlhe casmlc hanzan In n m quotlvllm quota W51 M u Ifwe wait long enough the night sky might become even brighter Light from the Big Bang 0 Every time we look at the night sky we are looking back in time It takes more than 4 years for light from the closest star to arrive It takes billions of years for light from the most distant galaxies to arrive 0 Can we see light from the Big Bang Almost he Last Scattering Epoch l a a a I K J p Li a 39 g y 9 h A Isgtmltmkin un m Wm Wm hanipman I May yazambmuhur 1h Winnmapch A 0 After 400000 years the Universe Minutes after the Big Bang cooled enough for electrons and the Universe was opaque 7 High temperatures kept all matter ions to recombine allowing light ionized to Pass 7 Photons could only travel a short The Universe was transparent distance before being absorbed Light from the Early Universe So what should light from 400000 tu years after the Big Bang look like 7 It should have a spectrum that corresponds to the temperature of the Universe at that time 3000 K 7 Expansion of space will stretch this light however The Universe has expanded by a factor of 1000 since this time so the wavelength will have stretched by the same amount 39 7 Spectrum will correspond to a 5 t emperature of 3K This light from the early Universe has been found and is called the Cosmic Microwave Background Brightness O l 2 3 4 Wavelength millimeters Light from the Early Universe Originally discovered by chance In the 1960 s scientists noticed microwave background noise in telephone satellite links No matter the direction a detector is pointed this background energy is constant nearly so Peak s at about 1 millimeter Wien s Law gives 3 K Once again the data came after Brightness a the theory but supports the theory l 2 3 A 5 Wuvelenglh mlllimelels Era of Galaxy Formation Using the Hubble Space Telescope we can image galaxies as they appeared nearly 13 billion years ago 7 These galaxies must have formed shortly after the Big Bang Galaxies must have been able to form relatively quickly 7 Gas clouds collapsed into disks 7 Gravity of visible matter doesn t appear to be strong enough 7 Dark matter was necessary to pull everything together Dark matter could form clumps in the early universe before the last scattering epoc u Hubble deepfield view 10000 These clumps should show up in the CMB galaxies less than 1 degree across and they do Red are hotter more dense regions blue cooler less dense Clumpiness in the CMB M v A r I n 39 I 6 r0 0 C I I 039 Q I 39 1169 f 39 WI r 7 H 39 i 41 v 1 0 5 opynghrb mewc mwr rll Companies lnc Parmiwonrzqmredlbrrepmdualonmdlsylay The Curvature of the Universe Remember that mass and energy can curve the space around it As the Universe expands the distances between the galaxies increases like galaxies painted on the surface of an in ating balloon Ifthe universe was like that expanding balloon but three dimensional travel in any direction would eventually bring you back to your starting place a closed universe Oth r Possible Curvatures of Space A Q Sum of arglzs gt 180 A l80 lt180 B C In addition to a closed universe or one with positive curvature of space there are two other options 7 Space could be at or have zero curvature B above 7 Space could be curved away from itself or have negative curvature or be open C above Geometry behaves differently with each curvature Extrapolating these 2D universes into 3D is very difficult Sum of nglex gt180 A If space is closed distant galaxies or clumps of mass will appear larger than they really are If space is at there will be no apparent distortion in size r 180 C If space is open distant objects will appear smaller than they really are Recent measurements show that space is very nearly at Abundance 1 02 074 0 6 078 10710 10 Fopynglnm ll icrmw mam lnc l39mimwm Wm fm rcpmmmmn 0mm 39me 5 l O 3 billion Neutrons 1 billion 300 million lt Tempemlure K 100 million hie rigin of Helium Immediately after the Big Bang only protons and electrons existed Shortly after the BB temperature and density was high enough for deuterium to form by fusion After 100 seconds or so temperature cooled enough so that deuterium could fuse into helium nuclei The temperature continued to cool and fusion stopped after a few minutes Big Bang theory predicts that around 24 of the matter in the universe is helium which matches what we measure today er and Antimatter an u o m AIcanHll Cnmpaums lnc velmmm m mqmmd m repmdutnou mm In the rst second of the early universe matter did not really exist rather everything was radiation or pure energy Cosmologists call this time period the early universe When energy is converted into matter I antimatter is formed as well Radiation creates particle and antlpanlcle For a pr0t0nantipr0t0n pair to form the temperature must be more than 1013 K Matter and antimatter annihilate on contact releasing energy There must have been an asymmetry in the amount of matter and antimatter formed in I I I order for there to be a predominance of Pamela and ampumde anmhdare creaking radiation ordinary matter today B Modern technology allows us to test theories back to a time 103933 seconds after the Big Bang to function at 103943 seconds after the BB a time called the Plank Time Using particle colliders scientists have uncovered a number of clues about what happened in the early universe after the Plank time The early universe underwent a period of very rapid expansion far greater than c 2 79 gt Phys1cs as we know 1t ceases 23 S i O M Th ED och of Inflation anvnglu x HIE MEGmIvHIll mum lIIc l tmIm mn Mum for munmm nrdwplm 1040 T Approx l072 Iy A 1020 Approx lOOIy E g I E C 3 10 20 In urion 1 sec NOW 10 40 I I I I l I I 10 45 10 35 10 25 10 15 10 5 l05 lOls Time seconds gt 0 By 103933 seconds the universe eXpanded from less than the size of a proton to the size of a basketball This eXpansion is called in ation In a on In ation may have created multiuniverses bubbles in the early mix that in ated separately splitoff and are entirely separate from our own universe nothing can pass between them including light In ation explains the uniformity of the universe the uniform CMB but also explains the irregularities the clumpiness of the CMB In ation explains Why the universe appears to be a at universe even though any geometry is possible In ation may explain why there are 4 dimension 3 space 1 time instead of the 10 or 11 of string theory perhaps these are the only ones that expanded during in ation This Set of Slides 0 This set of material starts the biggest picture Cosmology the study of the structure and evolution of the universe 0 This set of slides deals with our own Milky Way Galaxy 0 It includes material from Units 70 71 72 and 73 A galaxy is a large collection of billions of stars The galaxy in which the Sun and our solar system is located is called the Milky Way From our vantage point inside the galaxy the Milky Way looks like a band of stars across the night sky with dark dust lanes obscuring the center of the band Jur Galaxy the Milky Way It is dif cult to know exactly what the Milky Way looks like from the outside 7 It s similar to trying to figure out What the outside of a building looks like when you can only be inside that building William Herschel who discovered the planet Uranus created a map of the Milky Way based on observations The orange dot is our Sun incorrectly too close to the center Because the Mflky Way l a a see 5 when we l in dire ans lying In the dlsk e see vary a hen w In tho he cm a ll me Milky Way A r H la in Many astronomers recognized that the galaxy was more likely diskshaped than spherical Being in the middle of the disk we observe a band of stars rather than a sphericallysymmetric distribution of stars I l 8 kiloparsecs l Jacobus Kapteyn improved on Herschel s view of the galaxy Using more modem equipment Kapteyn attempted to count the number of stars in the galaxy and estimate their distance from the Sun The model was called Kapteyn s Universe as the existence of other galaxies was unknown 3 kiloparsecs He revised the size of the galaxy to around 18000 parsecs 18 kiloparsecs or kpc still with the Sun near the center Both Herschel and Kapteyn were correct in depicting the shape of the galaxy as a disk with most of the stars lying in more or less the same plane the galactic plane Harlow Shapley used observations of globular clusters to correctly deduce the location of the Sun within the Milky Way He reasoned that if the Sun were at the center of the galaxy then globular clusters would be found in all directions WM wanmu m we Wm mmamld n He noted that there were more globular clusters found in the direction of Sagittarius than elsewhere Therefore the center of the galaxy must be in the vicinity of Sagittarius Estimating Size While Herschel and Kapteyn both underestimated the size of the Milky Way galaxy Shapely estimated too large a slze Herschel 25 kpc Kapteyn 18 kpc Shapely 100 kpc Actual 3040 kpc Why the range Shapely s estimate too large due to 7 interstellar dust which makes stars look dimmer thus further 7 an overestimation of luminosity of variable stars used to calculate distances Today we know that the Milky Way is a spiral galaxy approximately 30 kps 100000 ly across The Sun is located around 8 kpc from the center in one of the spiral arms Most of the stars are concentrated in the galactic plane or in the central bulge at the center of the galaxy Inside the bulge is the nucleus of the galaxy luapm I Surrounding the disk is a roughly spherical distribution of stars called the halo Globular clusters are distributed throughout this halo surrounding the center of the galaxy Pznmwnn eqmmd rm WWW mmspvlay 5 Pop and Pop Astronomer Walter Baade observed an interesting segregation between stars in neighboring galaxies 7 Younger blue stars were found mostly in the disks and spiral arms He called these Population I stars Typically less than a few billion years old Follow circular orbits in the galactic plane 7 Older red stars were found mostly in the halo and central bulge He called these Population II stars More than 10 billion years old Follow random elliptical orbits around the galactic center 7 not necessarily in the plane These two types are in the Milky Way too Once this difference between Popub onlandllsuusuas noted astronomers could map our galaxy s arms Population I stars are mostly bnghnl uesUHshotCand B stars found in the disk By measuring the location of O and B stars near the Sun the first maps of the Milky Way s spiral structure were produced Dust and gas obscure the light from more distant stars so the map is incomplete OrionCygnus arm Way s Spiral Arms Fopyngln a m mammal Compamex Inc Vnnmwan Inquirer forrcprodncuon nrdwplay 260 1on Perseus arm I I Our galaxy likely began 13 billion years ago as a huge cloud of pure hydrogen and helium slowly rotating and collapsing The first stars formed Within this cloud burning out quickly and violently This added heavy elements to the cloud Population II stars formed next capturing some of the heavy elements and settling into elliptical orbits around the center of the cloud As the collapse continued a disk formed and Population 1 stars formed from the ashes of dying Pop 1 stars H Galactic Cannibalism H 0 There are a few observations that are not explained by this model Some stars follow unusual orbits in the galaxy Not all Pop 11 stars are the same age Model predicts that the first stars might not have been very massive and should still be around 0 Galactic cannibalism provides some answers The Milky Way may be absorbing another galaxy Observations show streams of stars coming from our galaxy s victim Co wnuhr if 39I he lcnre lhll 39omname c The Sombrero Galaxy v nu The Interstellar Medium ISM n Penmsnmi re39 uire for re nn ucxinn u i My Is space empty or not Clouds of cold gas Clouds of dust In a galaxy gravity pulls the dust into a disk along and within the galactic plane This dust can obscure visible light from stars and appear to be vast tracts of empty space Fortunately it doesn t hide all wavelengths of light Emission Nebulae We frequently see nebulae clouds of interstellar gas and dust glowing faintly with a red or pink color Ultraviolet radiation from nearby hot stars heats the nebula causing it to emit light This is an emission nebula Reflection Nebulae When the cloud of gas and dust is simply illuminated by nearby stars the light re ects Dusrcloud quot V quot H quot 39 creating a re ection nebula These typically glow Starlight reflected from dust grains Dark Nebulae Nebulae that are not illuminated nor heated by nearby stars are opaque they block most of the Visible light passing through it 0 This is a dark nebula Open slur cluster Dork nebula Light passing through an interstellar cloud can hold clues as to the cloud s composition Atoms in the cloud absorb speci c frequencies of starlight passing through creating absorption lines Astronomers can analyze these spectra to determine What the clouds are made of Composition of Interstellar Clouds Dork absorption lines in star39s spectrum Star39s absorption lines II II U gt Gos39s absorption lines Gas cloud Stor i V Atoms absorb some 39 wavelengths creating 7W l additional absorption lines N 39Qn at Spectra show that interstellar gas clouds are made of mostly hydrogen and helium just like the Sun and all stars 0 Dust particles do not absorb light the same way that gas atoms do but using similar methods tells us that the dust is made of silicates Heating and Cooling in the ISM Gas in the ISM is heated by radiation from nearby stars and by stellar winds Gas is cooled by reradiating away energy especially clouds that are shielded shadowed by dust or other cooler stars 0 and B stars are very good at heating as they put out so much UV radiation These UV photons can ionize neutral hydrogen with two effects 7 Causes gas to glow a reddishpink Liberated electrons emit radio waves that can be detected A 7 These radio waves penetrate dust well allowing us to map the galaxy 39 O 39 I O I O O O O 0 Staremits photons over wide range of wavelengths Dust portlcles scatter blue light Red lighi is less affected l opvnghv 1 he Mcnmwnm comm m Pcnmmm required Fortepmducnmv display Electron Proton Electron Flips over emitting cm wavelength radio waves 21 cm Radiation Most interstellar gas is very cold so it emits very few photons The electron in a hydrogen atom has two energy states 7 Spin up and spin down 7 Spin up has slightly more energy than spin down Ifthe electron s spin ips from up to down it must emit a photon of the same energy as the energy difference between states This 21 cm radiation HI emission is detected by radio telescopes allowing the study of these cold clouds sm mm In a The lVlilky Way does not rotate like a solid disk 7 Inner parts rotate about the center faster than outer parts 7 Similar to the way planets rotate around the Sun 7 This is called di erential rotation A plot of rotation speed vs distance is a rotation curve A star is held in orbit around the galactic center by the gravity of all matter within its orbit The rotational velocity of the Sun around the center of the galaxy can be used to estimate the galaxy s mass The combined gravitational effect of all mass within the Sun s orbit is equivalent to one large lump of mass at the center of the galaxy Mass of the Galaxy Newton s Law of Gravitation shows that the mass of all matter within the Sun s orbit is 9x1010 solar masses We can estimate the mass of the entire galaxy be measuring the orbital velocity of small satellite galaxies in orbit around the Milky Way 2x1012 solar masses The Galahtic Center and Edge 0 Despite the appearance of being Density is much higher at the core closely spaced stars in the Milky 7 Exceeds 100000 stars per cubic Way are very far apart P51350 7 At the Sun s distance from the Xray and gamma ray telescopes center stellar density is around 1 star reveala supemlasswe blaCk hOIe at per 10 cubic page the Milky Way 5 core 7 Called Sag Aquot 7 5 million solar masses KeckUCLA sumac 6mm Swan Spiral arm region Young star cluster region and H aners39ellar cloud 2 cloud emers arm is compressed I cloud and ccHapses approaches arm forming vars Star and gas orbit This set of slides This set of slides primarily covers the lateinlife evolution and death of massive stars stars gt 8 solar masses There s a Special and General Relativity discussion partway through The last part of this set covers black holes Units covered in order 66 67 53 and 68 This set will likely take more than one lecture to complete Formatidn of Heavy Elements 7 Hydrogen and a little helium were formed shortly after the Big Bang ALL other elements were formed inside stars Lowmass stars create carbon and oxygen in their cores at the end of their life thanks to the high temperature and pressure present in a red giant star Highmass stars produce heaVier elements like silicon magnesium etc up through iron by nuclear fusion in their cores 7 Temperatures are much higher 7 Pressures are much greater Highestmass elements heavier than iron must be created in supernovae the death of highmass stars The Li f spinan of a Massive Star 1 I I Ironcovefolms Jylr Supernova r igsmg hecvyieilerniems 39Fus39ing Hellum m core Red sueriqn39 39 YeHowG n 39 39 6 9 2 39u39 o 5 E 3 Mom sequence 39 r 00 Temperature K o lt Sun lor comparison Red giunl Approx 100 limes diomeler of Sun Core of red giant approx diameter of Eorlh of Fusion Reactions As a massive star burns its hydrogen helium is left behind like ashes in a replace Eventually the temperature climbs enough so that the helium begins to react fusing into carbon Hydrogen continues to fuse in a shell around the helium core Carbon is left behind until it too starts to fuse into heavier elements A nested shelllike structure forms Once iron forms in the core the end is near lapse of Massive Stars 7 Iron cannot be fused into any heavier element so it collects at the center core of the star Gravity pulls the core of the star to a size smaller than the Earth s diameter The core compresses so much that protons and electrons merge into neutrons taking energy away from the core The core collapses and the layers above fall rapidly toward the center Where they collide With the core material and bounce The bounced material collides With the remaining infalling gas raising temperatures high enough to set off a massive fusion reaction 7 an enormous nuclear eXplosion This is a Type 11 lb or Ic supernova me for a Supernova The luminosin spikes when the explosion occurs and then gradually fades leaving behind a E 6 O Lquot E O 5 E 3 I 100 200 Time days iSupernova Remnant The supernova has left behind a rapidly expanding shell of heavy elements that were created in the explosion Gold uranium and all other heavy elements all originated in a supernova Type II eXplosion The Crab Nebula ypes of Supernovae Type la The explosion that results from a White dwarf exceeding the Chandrasekhar Limit 14 solar masses Type II Supernovae resulting from massive star core collapse Less common 7 Type Ib and lo Result from core collapse but lacks hydrogen lost to stellar winds or other processes S L Stellar Corpses Hmmmo upm 2 Ourevlayerslullinwurd I 35wlodiunxclypelt A warm a hem lamAce supernova and Mamva m pmhapi in red glam stage mm all fuelconwma m Mnnlva var pcmovu e a pulsar A type II supernova leaves behind the collapsed core of neutrons that started the explosion a neutron star If the neutron star is massive enough it can collapse forming a black hole Fopynglrr 0 I1quot M m A Surprise Discovery Jocelyn Bell a graduate student working with a group of English astronomers discovered a periodic signal in the radio part of the spectrum coming from a distant galaxy Astronomers considered brie y the possibility of an alien civilization sending the regular pulses More pulsating radio sources were discovered These were named pulsars All pulsars are extremely periodic like the ticking of a clock In some cases this ticking is amazingly fast Spm m An idea was proposed that eventually solved the mystery A neutron star spins very rapidly about its axis due to conservation of angular momentum If the neutron star has a magnetic eld this field can form jets of electromagnetic radiation escaping from the star An Explanation 0 mm m mammal m Mme WM rm zpcnuucm mum We see a palm when beam pmms m Em If these jets are pointed at Earth we can detect them using radio telescopes As the neutron star spins the jets can sweep past earth creating a signal that looks like a pulse Neutron stars can spin very rapidly so these pulses can be quite close together in time Brighlness 0 01 02 03 Rotation speed gt Wham lher mwr ill am am lnc l39mmwun inquired lbrrcpmdummu nrdupla Glitches Time gt Slowing Down Over time the spin rate of a pulsar can decrease at a small but measurable rate Sometimes the pulsar s diameter shrinks slightly causing a momentary increase in the pulsar s rotation These glitches are short lived and the spin rate begins to decrease again Cmyngl039fhellbiraw il Campanies In m Rigid crust perhaps iron Approx c Few Neutron hundred meters superfluid in interior Approx 10 km about 6 miles HighEnergy Pulsars Most pulsars emit both Visible and radio photons in their beams Older neutron stars just emit radio waves Some pulsars emit very high energy radiation such as Xrays Xray pulsars Magnetars Magnetars have very intense magnetic fields that cause bursts of Xray and gamma ray photons Galilean Relativity 0 Galileo noted that the speed V of a thrown object depends 39 on how fast and in what Ru e Joveli s s eecl v spa er felony mime gt gt d1rectlon the thrower 1s gt mov1ng Juvelin s speed V VR rem 9Wquot 7 If the thrower is moving in the same direction as the throw the projectile goes I faster Runner s Ju velin 5 speed VJ Lead VR reamm rower gt i If the thrower 1s mov1ng 1n mews speed Vin the oppos1te d1rectron the mm mm projectile goes slower Velocities can add up he MichelsonMorley Experiment er 0 In the 1880 s Michelson and Morley devised an experiment to detect the motion of the Earth through the aether a universal atmosphere Light should move slower in the direction of the Earth s motion through space Detected no difference in speed A null result No aether plus the speed of light seemed to be a constant Water waves travel in water Sound waves travel in air What does light travel in Aether Or not The Lorentz Factor 0 It was proposed that perhaps matter contracted while it was moving reducing its length in the direction of motion 0 The amount of contraction was described by the Lorentz factor At slow speeds the effect is very small At speeds close to the speed of light the effect is dramatic E u 2 E z e 3 speed kmsec An Explanation Albert Einstein proposed that light did not behave classically Two postulates of Special Relativity The laws of physics are the same in every inertial reference frame The speed of light in a vacuum always has the same value no matter how fast the source of light and observer are moving relative to each other These postulates mean There is NO experiment you can do in a constantvelocity inertial reference frame that would prove Whether you are moving or not Traveling at say half the speed of light and turning on a ashlight the light from the ashlight will leave you at c and anyone else measuring that light will also measure 0 no matter their speed relative to you Einstein s Insights arting from these assumptions Einstein realized Length contracts in the direction of motion by a fraction equal to the Lorentz factor Time stretches dilates as well also by the Lorentz factor Mass increases with motion Moving clocks run slow Moving objects reduce their length in the direction of motion Einstein s Special Relativity Time dilation and length contraction depend on the observer 7 To an observer on Earth the spacecraft s clock appears to run slow and the ship looks shorter 7 To an observer on the ship the Earth appears to be moving in slowmotion and its shape is distorted The passage of time and space are relative Space is a 4th Dimension Possibilities for Space Travel Example A spacecraft leaves Earth heading for a star 70 lightyears away traveling at 99c 7 To an observer on Earth it takes the spacecraft just over 140 years to get to the star and then back again 7 To passengers on the ship it only takes 20 years for the roundtrip This means that high speed travel to the stars is possible but comes at the cost of friends and family The velocity necessary to avoid being gravitationally pulled back to an object the escape velocity is Vex l ZGM R Note that as R decreases the escape velocity increases A White dwarf s escape velocity is around 6000 kms ten times faster than the Sun s A White dwarf is around 100 times smaller than the Sun The Escape Velocity Limit Also recall that nothing can travel faster than the speed of light 6 or 3gtlt108 ms If a stellar core is compressed so much that its radius is smaller than 2 x G x M C 2 the Schwarzschild radius then nothing can escape from its gravitational force including light The core would become a black hole Rs Einstein s Theory of General Relativity Equivalence Principle There is NO experiment that you can perform that can tell you Whether an acceleration is due to gravitational force or an accelerating reference frame In other words being stationary in a gravitational eld is equivalent to being accelerated in a constant acceleration frame of reference If you are on a spacecraft and drop an apple A consequence of this Gravity de ects light Which has no mass and thus Newton s Law says won t be effected Mass Warps Space Mass warps space in its Vicinity The larger the mass the bigger dent it makes in space Objects gravitationally attracted to these objects can be seen as rolling downhill towards them If the mass is large enough space can be so warped that obj ects entering it can never leave a black hole is formed mu 4me mln my If a stellar core is massive enough it Will not stop collapsing when it becomes a neutron star The radius of the core continues to shrink and density continues to increase Eventually the core is compressed to a single point called a singularity NOTHING can escape from this black hole Once something including light crosses the event horizon escape is impossible Black Holes 6 Photon unable to mvel oulwurd eflecllcn ofllgN by curve spate Viewing a black hole If light cannot escape a black hole how can we see one You can t Directly If a black hole is in orbit around a companion star the black hole can pull material away from it This material forms an accretion disk outside of the event horizon and heats to high temperatures As the gas spirals into the black hole it emits Xrays which we can detect Light curves from a black hole binary system Companion um General Relativity continued Einstein predicted that not only space would be warped but time would be affected as well The presence of mass slows down the passage of time so clocks near a black hole will run noticeably slower than clocks more distant The warping of space has been demonstrated many times including by observations of the orbit of Mercury The slowing of clocks has been demonstrated as well Mercury ravitational Redshift Cnpyiigln e m Mcnmw inu mmpmm n Fermisi mn required cm Rpm an u an my Bull roHing up a mu uses energy light moving away from a star loses energy and slows down Photons traveling away from a massive object will experience a gravitational redshift Their frequency will be shifted toward the red end of the spectrum


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Jim McGreen Ohio University

"Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."

Jennifer McGill UCSF Med School

"Selling my MCAT study guides and notes has been a great source of side revenue while I'm in school. Some months I'm making over $500! Plus, it makes me happy knowing that I'm helping future med students with their MCAT."

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.