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Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 24 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 1 Was Due Today– L24 • Reading: – (Unit 5) • Pre-Lecture Reading Questions: – Unit 5 Revision (if desired): Stage 2 • End-of-Chapter Quizzes: – Chapter 16 • Papers: – Paper 3 Revision (if desired): • Stage 2 due Monday Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 2 Unit 5: Big Objects 1.Galaxies 2.Star Birth and Death 3.More on Black Holes Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes Today 3 Where are we now in the history? Half a billion years after the bang Black holes start forming Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 4 Paper 4: The Assignment • Abbreviated Description: What is the evidence for Stellar Black Holes? Note there is an emphasis on what is a black hole and how it forms. – Explain it to someone who isn’t taking the class (no jargon) • Make sure you read ALL the instructions • Same format and due dates as usual – Text due 1 week after we finish Chapter 17 – Calibration, reviews and self-assessment due a week after that Big Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 5 Outline • What makes Black Holes black • What a black hole would look like to a nearby observer • Evidence for Black Holes • Different types of Black Holes • A few words on why black holes are so important in cosmology and our understanding of the Big Objects and Black Holes Big Bang, Black 6 Big Bang Topic 3: Properties of Black Holes Holes, No Math Moving Towards Black Holes • If a neutron star has a “critical mass” (about 3MSun) it can continue to collapse • Nothing strong enough to oppose the crush of gravity! Continues to collapse until it becomes a single point in space • Call this a Black Hole Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 7 Why do we call it a black hole? Call it a Black Hole because light can’t “escape” Say more about what this means Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 8 What they are… and aren’t • Black holes aren’t demonic, sucking power holes • A black hole is just another thing a star can turn into when it runs out of fuel • It is basically a really massive ex-star • Then again, something with that much mass but a size smaller than a proton does have some unusual properties Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 9 The Sun in Space • What if the Sun compressed into a Neutron Star? • Shrink Sun to 10% of its size • Now 1% • Neutron star is 0.004% of its size • What if it were crushed into a 1.4 Million Kilometers across black hole? Big Objects and~25 Black Holes Big Bang, Black Kilometers across 10 Holes, No Math Topic 3: Properties of Black Holes The Curvature of Space-Time near the Sun The size of the Sun… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 11 How the Curvature Changes as we Compressing the Sun What if we compressed the Sun into a Neutron Star? Far outside the Sun you can’t really tell the difference You can tell the difference if you are very close to the Sun itself The sun is now a few kilometers across Big Objects and Black Holes Big Bang, Black Topic 3: Properties of Black Holes Holes, No Math 12 Compress the Sun into a Black Hole Infinite curvature Big Bang, Black Holes, No Math • Black hole is just a point in space • Here we looking at the CURVATURE of Space-time • Far outside the Sun the curvature isn’t very different, but very close to the center is very different Big Objects and Black Holes Topic 3: Properties of Black Holes 13 What does this have to do with light being able to escape? Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 14 Small speed objects can’t leave the Earth How fast does it need to move so that it can “escape” the pull of gravity? Call this the escape velocity Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 15 The Moon has a “small” escape Velocity Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 16 The Escape Velocity for the Earth Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 17 The Sun Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 18 A Neutron Star Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 19 A Black Hole Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 20 Why do we call it a Black Hole? A Black Hole is so dense that it’s escape velocity is GREATER than the speed of light light can no longer escape! Looks at this from the perspective of the curvature of Space-Time Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 21 Space-Time as an Escalator Can think of space near a star as an escalator moving downward towards the surface of the star A person in curved space-time moves downward Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 22 Later time Even though he is walking in the “up” direction, his overall motion is actually downwards Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 23 Even later times. If the man moves slower than the speed of the escalator he will move backwards If the escalator is moving down faster than the speed of light, even light can’t go “up” Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 24 Space-Time Near a Black Hole • The gravity of a Black Hole curves space-time SO MUCH that light simply can’t leave • If light can’t escape then we can’t “see” light from it and our star “appears” black • Since light could fall in, and never come back out, we call it a “Black Hole” Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 25 Black Holes Light falls in and never comes back Light from inside can’t escape! Path of light passing nearby gets bent Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 26 Weird… What if our Sun were to (magically??) turn into a Black Hole? The gravitational attraction far outside wouldn’t change, so the planets would continue to orbit Then again, without the light it would get really cold and we’d all die… Big Objects and Black Holes Big Bang, Black 27 Holes, No Math Topic 3: Properties of Black Holes Different Types of Black Holes • Two different types 1. Stellar Black Holes (the types we have been discussing) 2. Supermassive Black Holes • Both have been observed and are now known to be common – Closest known stellar Black Hole is about 3,000 light years away • Supermassive Black hole at the center of the Milky Way with a mass more than one million times that of our sun – At the center of many (all?) large galaxies Big Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 28 Some pictures from Chapter 2 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 29 Supermassive Black Holes • Still learning about how they came to be. Some people think they started as a stellar Black Hole near the center of the galaxy when the galaxy was forming a half a billion years after the bang – “Ate” material that fell towards the center of the galaxy – Lots of light came from the atomic interactions as the material fell in – Called a Quasar • Today: nothing falling in since everything either already fell in or is now rotating around the center of the galaxy – Quasars onlyBigobserved in “distant” galaxies Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 30 Switch Topcs • Life near a black hole • Evidence for black holes Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 31 Getting a Close-Up Look What would a Black Hole look like to an observer who tries to get a closer look? Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 32 An Astronaut Near a Black Hole Light falls in and never comes back The same thing is true for our Astronaut Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 33 Event Horizon • A rocket with a speed of 11km/sec can escape from the Earth – Needs a lower speed if it starts up high in the atmosphere – The higher it is, the smaller the escape velocity is • We call that special distance from the center of a black hole where the escape velocity is equal to the speed of light the EVENTBigHORIZON Objects and Black Holes Big Bang, Black 34 Holes, No Math Topic 3: Properties of Black Holes Spaghettification as he falls in… • The gravitational pull on his feet would be much stronger than on his head • He’d get stretched out and then ripped apart Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 35 Falling into a Black Hole Spaghettification as he falls in Can’t see him after he passes the event horizon… not even Big light from can escape 36 Objects and his Blackgun Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes A way to observe Stellar Black Holes? • Let’s say we have two stars orbiting each other (a binary pair), and one has already turned into a black hole • We can “see” light “from” a Black Hole by watching them “eat” their Big Objects and Black Holes Big Bang, Black companion Topic 3: Properties of Black Holes Holes, No Math 37 Black Holes Suck • Can think of the stuff sucked in like crumbs on the surface of the water as it goes down the sink swirl faster and faster until it reaches the drain and gets sucked down • As the matter moves more quickly the atoms collide • These collisions produce light that we can see x-rays Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 38 A way to observe Supermassive Black Holes • Can observe supermassive black holes by looking at stars as they orbit “nothing” at the center of a galaxy • Can even measure their mass like the way we measure the mass of the Sun Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 39 Measuring the Mass of a Stellar Black Hole Can also measure the mass of a stellar black hole if its in a binary pair by watching the speed of its “partner” orbit Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 40 Last Topic on Black Holes… Why are Black Holes important in Cosmology? Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 41 Theory In the 1970’s Hawking and Penrose realized that the creation of a Black Hole looks like a Big Bang in reverse Said differently, the Big Bang appears to be the creation of a Black Hole running backward in time… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 42 Theory? • Inside a Black Hole we get “infinite curvature” and “infinite density” of space – A singularity • Here the particles would interact according to Quantum Mechanics • Hard to calculate things… Quantum Mechanics and General Relativity predict different things and we don’t know which one is right… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 43 In a way, this is Good… • Since we now have observed Black Holes, we finally have a set of objects we can look at • Maybe by studying their properties we can tell which theory (if either) is correct • Maybe neither? Maybe something like Quantum Gravity? String Theory?… Stay tuned… 44 Big Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes Paper 4: The Assignment • Abbreviated Description: What is the evidence for Stellar Black Holes? Note there is an emphasis on what is a black hole and how it forms. – Explain it to someone who isn’t taking the class (no jargon) • Make sure you read ALL the instructions • Same format and due dates as usual – Text due 1 week after we finish Chapter 17 – Calibration, reviews and self-assessment due a week after that Big Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 45 For Next Time – L24 No class Wednesday, but everything is still due as scheduled • Reading: – Unit 6 • Pre-Lecture Reading Questions: – Unit 6: Stage 1 • End-of-Chapter Quizzes: – Chapter 17 if we finished Chapter 17 (else just Chapter 16) • Papers: – Paper 3 Revision (if desired): • Stage 1 due Monday before class – Paper 4: • Due 1 week from today if we finished Chapter 17 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 46 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 47 Clicker Question Can you "fill up" a black hole? a) Yes b) No Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 48 Clicker Question Can a Black Hole orbit another star? a) Yes b) No Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 49 Clicker Question Could the Earth orbit a black hole? a)Yes b)No Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 50 Clicker Question What would happen if two black holes collided? a)They would make a supermassive black hole b)They would just make a black hole that is the mass of the two black holes that started c) Black holes can’t collide Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 51 1 Paragraph in-class Quiz What is the evidence for stellar black holes? Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 52 For Next Time – L23 • Reading: – Unit 6 • Pre-Lecture Reading Questions: – Unit 6: Due Monday before class • End-of-Chapter Quizzes: – Chapter 17 if we finished Chapter 17 (else just Chapter 16) • Papers: – Paper 3 Revision (if desired): • Stage 2 due Wednesday before class – Paper 4: • Due 1 week from today if we finished Chapter 17 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 53 For Next Time – L24 • Reading: – Unit 6 (was due already) • Pre-Lecture Reading Questions: – Unit 6: Stage 2 due Wednesday before class • End-of-Chapter Quizzes: – Chapter 17 • Papers: – Paper 3 Revision (if desired): • Stage 2 due Wednesday before class – Paper 4: • Stage 1 eue 1 week from today (Monday) Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 54 Was Due for Today– L25 • Reading: – Chapter 18 • Pre-Lecture Reading Questions: – Chapter 18 • End-of-Chapter Quizzes: – Chapter 16 (also check 14) • Papers: – Paper 3: Done fixing broken rubrics. Now working on recent re-grade requests. – Paper 3 Revision: Now open for submission. Text due Monday before class Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 55 Was Due for Today– L26 • Reading: – Chapter 20 • Pre-Lecture Reading Questions: – Chapter 20 • End-of-Chapter Quizzes: – Chapter 16 (also check 14) • Papers: – Paper 3: Working on recent re-grade requests. – Paper 3 Revision: Now open for submission. Text due Monday before class – Paper 4: Now open for submission. Text Bigbefore Objects and Black Holes Big Bang, Black 56 due Monday class Holes, No Math Topic 3: Properties of Black Holes Prep for Next time – L25 • Reading: – Chapter 19 and 20 • Pre-Lecture Reading Questions: – Chapter 19 and 20 • End-of-Chapter Quizzes: – If we finished Chapter 17 then end-of-chapter quiz 17 (else just through Chapter 16) • Papers: – Paper 3: Done fixing broken rubrics. Now working on recent re-grade requests. – Paper 3 Revision: Now open for submission. Text due Monday before class – Paper 4: Due one week from today Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 57 Was due today – L12 • Reading: –BBBHNM: All reading through Chapter 19 •Reading Questions: – All reading questions through 19 • eLearning Quizzes: – Chapter 17 • Papers: – Rest of Paper 3 assignment (if you resubmitted a revision) due before class today – Text of Paper 4 due Wednesday night at 11:55PM Big Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 58 End of the Semester – L12 • Only 3 more days of class – Today, April 22nd, and April 29th • Need to finish all the end of Chapter quizzes as well as AMS 2 – That’s my of semester evaluation (there will be another) – Need to finish this before you can finish all the end of chapter quizzes • Will not do the 5th paper, but will allow Early Times & Fate of the Universe Topic 1: Big Objects and Black Holes Big Bang, Black 4 revision Possibilities a paper 59 Holes, No Math Topic 3: Properties of Black Holes Prep For Next Time – L11 • Reading: –BBBHNM: All reading through Chapter 19 • Reading Questions: –All reading questions through 19 • eLearning Quizzes: – Through Chapter 17 • Papers: – Rest of Paper 3 assignment (if you resubmitted a revision) due before class on Monday – Paper 4 will due Wednesday at 11:55PM and the Calibrations/Reviews/Self-Assessment will be due Monday before class. Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 60 Prep For Next Time – L11 • Note: May change depending on how far we get in lecture • Reading: –BBBHNM: All reading through Chapter 19 • Reading Questions: –All reading questions through 19 • eLearning Quizzes: – If we finished Chapter 16 then end-of-chapter quiz 16 (else just through Chapter 15) • Papers: – Rest of Paper 3 assignment (if you resubmitted a revision) due before class on Tuesday – Since we did not finish Chapter 17, Paper 4 will be assigned Tuesday Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 61 Prep for Today (Is now due) – L23 • Reading: – BBBHNM 18 • Reading questions: – Chapter 18 • End-of-Chapter Quizzes: – Chapter 16 • Paper Stuff – Paper 3: Misgraded? Let us know • Revision due Monday before class. Want feedback? Due Thursday – Paper 4: Will be due 1 week after we finish Chapter 17 Big Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 62 Prep for Today (Is now due) – L23 • Reading: – BBBHNM 18 • Reading questions: – Chapter 18 • End-of-Chapter Quizzes: – Chapter 16 • Paper Stuff – Paper 3: Misgraded? Let us know • Revision due Monday before class. Want feedback? Due Thursday – Paper 4: Will be due 1 week after we finish Chapter 17 Big Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 63 Prep for Today (Is now due) – L24 • Reading: – Rest of BBBHNM • Reading questions: – Some of the rest of the chapter, finish all by the end of the semester • End-of-Chapter Quizzes: – Chapter 16 • Paper Stuff – Paper 3: Misgraded? Let us know – Paper 3 Revision: Due Monday before class. Want feedback? Due Thursday – Paper 4: Will be due 1 week after we finish Chapter 17 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 64 Prep For Next Time – L12 • Note: May change depending on how far we get in lecture • Reading: –BBBHNM: All reading through Chapter 20 • Reading Questions: – All reading questions through 20 • eLearning Quizzes: – If we finished Chapter 17 then end-of-chapter quiz 17 (else just through Chapter 16) • Papers: – Text of Paper 4 assignment due before class on Tuesday Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 65 Prep for Next Time – P23 • Reading – Reading the rest of BBBHNM • Reading questions – Chapter 18, 19 and 22 (can do in installments) • End-of-Chapter Quizzes – If we finished Chapter 17 then end-of-chapter quiz 17 (else just 16) • Papers – Paper 2 Revision or Paper 3: Misgraded? Let us know. – Paper 3 Revision: Due Monday before class. Want feedback? Due Friday for quick response – Paper 4: Final date assigned when we finish 17 Big Objects and Black Holes Big Bang,Chapter Black Holes, No Math Topic 3: Properties of Black Holes 66 Full set of Readings So Far • Required: – BBBHNM: Chaps. 1-18 • Recommended: • TFTM: Chaps. 1-5 • BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137), 12 • SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (up-to-page 164) • TOE: Chaps. 1-3 • Seeds (Cosmology in the 21st Century) Big Bang, Black 67 Big Objects and Black Holes Topic 3: Properties of Black Holes Holes, No Math More on Our Astronaut • Suppose he sends us a signal every second, according to his watch, as he falls in • As he falls into the star space-time gets stretched more and more – The time between signals gets stretched also – His signals appear to get further and further apart in time – His signals are red-shifted Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 68 Astronaut Continued • Any light reflecting off him is red-shifted also, so he looks “redder and redder” • Eventually, his signals “fall” into the Black Hole and we can’t see them (or him) anymore Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 69 Prep for Next Time – P22 • Reading – BBBHNM 18 • Reading questions – Chapter 18 • End-of-Chapter Quizzes – If we finished Chapter 17 then end-of-chapter quiz 17 (else just 16) • Papers – Paper 2: Misgraded? Let us know – Paper 3: Misgraded? Let us know – Paper 4: Will assign paper 4 next time Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 70 Announcement before we begin Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 71 Time near a Black Hole The passage of time for an observer near or on a Black Hole is different than we observe because spacetime is different in curved space Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 72 Evidence for Black Holes? Hubble Space Telescope data Cygnus XR-1 Look at the hot gas swirling around “Nothing” A “blob” breaks off then swirls in and disappears like an astronaut would Big Objects and Black Holes Big Bang, Black http://oposite.stsci.edu/pubinfo/pr /2001/03/content/CygnusXR-1.mpg Holes, No Math Topic 3: Properties of Black Holes 73 How do we Observe Black Holes? • We can “see” Black Holes “eating” other stars • They are so massive that the gravitational attraction can “suck” off stuff from another star Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 74 Black Holes Suck • Can think of the stuff sucked in like crumbs on the surface of the water as it goes down the sink swirl faster and faster until it reaches the drain and gets sucked down • As the matter moves more quickly the atoms collide • These collisions produce light that we can see Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 75 The Sun in Space-Time The size of the Sun… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 76 Compressing the Sun What if we compressed the Sun into a Neutron Star? Far outside the Sun you can’t really tell the difference You can tell the difference if you are very close to the Sun itself The sun is now a few kilometers across Big Objects and Black Holes Big Bang, Black Topic 3: Properties of Black Holes Holes, No Math 77 Light in Space-Time • Doesn’t light just always travel at the speed of light? • Yes, but it’s path can curve in space-time… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 78 The Sun in Space-Time Anything faster than 620 km/sec can escape Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 79 Neutron Stars Only things faster than half the speed of light can escape Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 80 Black Holes Nothing can escape unless it is traveling faster than the speed of light No matter how fast it’s going it can’t leave Space is falling into the hole too Big Bang, Black quickly Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 81 Papers • Paper 1 is done • Paper 2 grades are on eLearning – Working on getting the revised grades fixed • Paper 3: – Let us know if you think you have been mis-graded – Revisions must be submitted by Wednesday at noon • Paper 4: – Now open – Due next Monday before class • Paper 5 (last paper, no final) – Assigned after we start Chap 20 Big 82 Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes Other Stuff • Elearning: –Unit 5 in progress • Make sure you pick up the latest version of the online textbook!!! –Been updating it all semester Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 83 The Reading So Far and For Unit 5 Reading for Unit 5: • BBBHNM: Chaps. 15-17 • SHU: 4(87-93) • TOE: 3 • BHOT: 8(76-85) Full reading through Unit 5: • BBBHNM: Chaps. 1-17 • TFTM: Chaps. 1-5 • BHOT: Chaps. 1-7, 8 (68-85), 9 and 11 (117-122) • SHU: Chaps. 1-3, 4(77-93), 5(95-114), 6, 7 (up-to-page 159) Objects and Black Holes • Bang, TOE:Black Chaps. Big 1-3 Big 84 Holes, No Math Topic 3: Properties of Black Holes For Next Time Unit 6: Early Times and the Fate of the Universe Full reading for Unit 6: • BBBHNM: Chaps. 18-22 • SHU: 8 (159-164) • BHOT: 11 (122-137), 12 • Seeds (Cosmology in the 21st Century, Web Handout) Full reading through Unit 6: • BBBHNM: Chaps. 1-22 • TFTM: Chaps. 1-5 • BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137), 12 • SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (up-to-page 164) • TOE: Chaps. 1-3 • Seeds (Cosmology in the 21st Century) Lecture prep: Turn in on eLearning Two questions from Chapter 18 you want to know the answer to Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 85 Overview • The way Galaxies and Stars form is very similar • The way stars “die” depends on the star itself… sometimes they die to form a Black Hole Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 86 The Life and Death of Stars Small Star (Red Giant) White Dwarf Big Star (Supergiant) Explodes (Supernova) Neutron Star Brown Dwarf Big Bang, Black Holes, No Math Black Hole Slightly more complicated than this… Big Objects and Black Holes Topic 3: Properties of Black Holes 87 Writing Assignments Short Assignments 1 & 2 Re-do’s are still possible. Want to revise again? Talk to me eLearning: Unit 4 now due Need to be working on Unit 5 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 88 Papers AFTER Paper 2 Two options 1.Two short papers like the first one • One on Black Holes (due one week after we finish Black Holes) • One on Dark Matter (due last day of class) 2.Research Paper If you want this option Stage 1 must be approved ASAP • Was due last week • Final paper due the last day of Big Objects and Black th Holes Big Bang, class, Black 89 Tuesday Dec 8 Topic 3: Properties of Black Holes Holes, No Math Outline • What makes Black Holes black • What a black hole would look like to a nearby observer • Black Holes ain’t so black… • A few words on why black holes are so important in cosmology and our understanding of the Big Bang Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 90 How do we Observe Black Holes? • We can “see” Black Holes “eating” other stars • They are so massive that the gravitational attraction can “suck” off stuff from another star Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 91 Black Holes ain’t so black… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 92 Quantum Mechanics Weird: Pairs of particles can be created but they have to disappear again quickly because of Quantum Mechanics e- e+ Big Bang, Black Holes, No Math Need to conserve energy Big Objects and Black Holes Topic 3: Properties of Black Holes 93 Black Holes ain’t so Black Even Weirder: Near a Black Hole the pairs of particles can get split up One gets sucked in and the other goes off and we can see it! e + e Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 94 So What? • By conservation of energy, one will have positive energy and the other will have “negative” energy • Since the negative energy particles fall into the black hole, by Einstein’s E=MC2 equation, the mass of the Black Hole goes down • To an observer at a distance the particle will appear to have been “emitted” from the Black Hole Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 95 Can a Black Hole “Evaporate”? • We can do the calculation… Estimates are that it will take 1066 years • Compare to the age of the Universe: 1010 years • In other words… don’t hold your breath… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 96 Can we see this? Example of a Black Hole • Stuff swirling into the middle • A stream of particles coming out Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 97 Black Holes Suck • Can think of the stuff sucked in like crumbs on the surface of the water as it goes down the sink swirl faster and faster until it reaches the drain and gets sucked down • As the matter moves more quickly the atoms collide • These collisions produce light that we can see Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 98 http://science.nasa.gov/headlines/images/blackhole/blackhole-swirl.jpg Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 99 Black Holes Nothing can escape unless it is traveling faster than the speed of light No matter how fast it’s going it’s path is back into the Black hole Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 100 Schedule from Here on Out • Wed Nov 19th: 25th lecture: – Recitation for Paper 2 • Please bring a copy of your outline and be prepared to discuss it • Will be checked off at the end of class as your in-class quiz – Inflation • Mon Nov 24th: 26th lecture: Dark Energy • Wed Nov 26th: No class – Research paper and 2nd short paper due at midnight – Day before Thanksgiving. Class cancelled • Dec 1st: No classes redefined day • Dec 3rd: Reading period, no classes • Dec 8th: Finals week, no final Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 101 What is a Black Hole? • A Black Hole is a really REALLY DENSE star • REALLY curves the space time around it… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 102 Escape Velocity • The escape velocity for the Earth is about 11.2 km/sec • The escape velocity for the sun is about 620 km/sec • The escape velocity of a neutron star is about half the speed of light! Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 103 Why do we call it a Black Hole? • The escape velocity for the Sun is about 620 km/sec • The escape velocity of a neutron star is about half the speed of light! • The escape velocity for a Black Hole is GREATER than the speed of light! Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 104 Paper 2 • On Wednesday we will devote the first part of lecture for small group discussions of your Short-Paper 2 • Please bring a copy of your outline and be prepared to discuss it • Will be checked off at the end of class as your in-class quiz Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 105 Schedule from Here on Out • Mon Nov 17th: 24th lecture: Black Holes • Wed Nov 19th: 25th lecture: – Recitation for Paper 2 – Inflation • Mon Nov 24th: 26th lecture: Dark Energy • Wed Nov 26th: No class – Research paper and 2nd short paper due at midnight – Day before Thanksgiving. Class cancelled • Dec 1st: No classes redefined day • Dec 3rd: Reading period, no classes • Dec 8th: Finals week, no final Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 106 That’s it • It’s been a real pleasure • Stay in touch, and best of luck in the future! Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 107 Remaining Assignments • Writing Assignments Due Thursday – However, you may turn it in, via email, on Monday – If you want to revise your paper you’ll need to pick it up from me directly • Don’t forget to finish your WebCT stuff Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 108 Next Time • Back to Section 5: Early Times and the Fate of the Universe –Inflation –Dark Energy Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 109 • Said differently, a Big Bang could occur provided only that General Relativity is correct and that the universe contains as much matter as we observe Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 110 • As the mass goes down the area of its event horizon goes down… • Might black holes eventually evaporate? • Estimates are that it will take 1066 years • Compare this to the 1010 years which is the age of the universe • In other words… don’t hold your breath… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 111 TOE 4 cont… • The smaller the black hole, the easier it is for one of the particles to escape • Thus the rate of emission will be greater and the apparent temperature of the black hole will be higher Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 112 TOE 4 cont… • The smaller the black hole, the less far the particle with negative energy will have to go before it becomes a real particle • Thus the rate of emission will be greater and the apparent temperature of the black hole will be higher • Since the negative energy particles fall into the black hole, by Einstein’s E=MC2 equation, the mass of the black hole goes down Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 113 So What? • By conservation of energy, one will have positive energy and the other negative energy • Real particles (electrons etc.) always have positive energy, however the gravitational field inside a black hole is so strong that even a real particle can have negative energy there • BHOT 10…It is therefore possible for virtual particles with negative energy to fall into a black hole and become real particles • Its partner may fall into the black hole also • However, since it has positive energy it is also possible for it to escape to infinity as a real particle • To an observer at a distance it will appear to have been emitted from the black hole Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 114 TOE 4 cont… • There can be quantum fluctuations in empty space • One can think of these fluctuations as pairs of particles of light or gravity that appear together at some time, move apart and then come together again and annihilate each other • These are known as virtual particles Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 115 Our Astronaut • Suppose he sends a signal every second, according to his watch, to us as he falls in • He begins transmitting at 2 seconds before 11:00 • What will the spaceship record? • TOE 3, p54 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 116 • Do we really want to spend time on HOW black holes are observed? • All the quasars we see are REALLY far away, which means we are observing them from a LONG time ago • The theory goes that they eventually turned into Black Holes and that’s why we don’t see them closer by… i.e., the ones closer by have already turned into black holes Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 117 Our Astronaut • Suppose we have an astronaut getting close to a Black Holeon the surface of a collapsing star and stays on the surface as it collapses • At some point on his watch, say 11:00 the star shrinks past the critical radius such that the gravitational field becomes so strong that nothing can escape Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 118 SHU 11 cont… • We believe there is a black hole at the center of our galaxy. Reading for this??? Actually quite common… • Describe Hawking radiation? • “Event Horizon?” • Jets of matter… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 119 Why do we believe in black holes? • Do they really exist? What is the evidence? Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 120 More Notes on Black Holes • Black holes have been observed and are now known to be common • There is a huge black hole at the center of the milky way with a mass more than one million times that of our sun • That supermassive black hole has a star orbiting it about 2% of the speed of light which is faster than the average speed of an electron orbiting the nucleus of an atom. Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 121 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 122 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 123 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 124 TOE 4 • Black holes ain’t so black. • Really want to talk about entropy and the 2nd law of thermodynamics • Anything with a temperaure (like a hot poker) emits radiation (light). • Black holes, like everything in quantum mechanics, is no different. Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 125 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 126 • This is some text Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 127 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 128 TOE 3… cont… • Call the event horizon the boundary from which light can just barely escape (or just barely not escape if you like). Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 129 TOE 4 cont… • Black holes emit radiation and particles as if it were a hot body with a temperature that only depends on the black hole’s mass: the higher the mass the lower the temperature. Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 130 • Figure on page 77 of BHOT. • This minimum speed is known as the “escape velocity” and we can use it for rockets. • It turns out that we can calculate the escape velocity for a star and as the star gets heavier and denser it gets. this value goes up Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 131 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 132 TOE 3… • Why can’t light escape? It moves at the speed of light… it doesn’t slow down light a rocket? • Space is bent so much by the black hole that the light simply curves back onto itself enough so that it can’t escape Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 133 BHOT 8 • Black Hole is a new word, Created in 1969 by Wheeler (year I was born) • Think of light as a particle, and therefore affected by gravity • If you shoot a cannon ball Model of throwing up a stone in the air. Small speed falls back down • Huge speed, like the space shuttle, it will leave the gravitational pull of the earth Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 134 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 135 • Eventually, this speed is so high that its faster than the speed of light!!! Thus light can’t escape, its pulled back in! • In other word all the light that a star emits will fall back into it and no light escapes, if no light escapes to us it will look BLACK and its as if the light is falling back into to a hole. Thus we call it a BLACK HOLE> • TOE 3 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 136 The curvature of the Sun today, yellow represents the sun itself The diagram on the right Sun compressed to the size of a white dwarf (about the size of the earth). Far outside the sun you can’t really tell the difference, but you can very close to the sun itself If the Sun were compressed into a black hole… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 137 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 138 Outline • How are black holes created? • Properties of black holes • Why are black holes so important in cosmology and our understanding of the Big Bang? Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 139 • The Biggest Objects in the Universe: Part 1 Maybe a week or two on black holes, then a week on all the other stuff? (Introduce all the really cool things we study in cosmology Blackholes, wormholes, supernova, white dwarfs, pulsars, MACHOs, galaxies, Red Giants…ect. Is there enough on this stuff… ) Peripheral in SHU and other books. Get the astronomy book? The toys and the experiments we use to look at all the cool things mentioned in the previous lectures…WMAP, Hubble, Radio telescopes…ect) Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 140 • The Rest of the Stuff in the Universe Part 1:(Introduce ideas of Dark Matter and how we know it is there, Dark Energy and what it means for our models of the universe, talk about experiments trying to find these things). This could be where we have our paper on funding for experiments searching for Dark Matter! Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 141 TCP 17 cont… • How black holes are formed • A black hole originates in the collapse of the iron core that forms just prior to the supernova of a very high mass star • Any star born with more than about 8MSun dies in a supernova (previous lecture), but most of the star’s mass is blown into space by the explosion. Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 142 • As a result most of the collapsed cores left behind by most supernovae become neutron stars • However, if the supernovae doesn’t blow away too much of the mass the remaining neutron star can have enough mass so that the neutron pressure cannot overcome gravity Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 143 SHU 5 • Picture of light rays going past a black hole on page 102 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 144 SHU 10 cont… • Black Holes continued… Page 210… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 145 TCP 17 cont… • Once the critical mass is reached nothing can hold back gravity and it collapses on itself and becomes a black hole. • This stretches space time • Cool pictures on page 529 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 146 BHOT 8 • Pictures on page 77 and 81 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 147 • Worm holes a little here… not sure what to say. Get back to BHOT first… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 148 TCP 17 cont… • Cool picture on page 532 of a person getting stretched… • Voyage to a black hole… clocks slowing down etc. Page 530. Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 149 TOE 3 cont… • Gravity waves • Black holes are spherical (like the earth) in general, but not all of them are this way. Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 150 How do we Observe Black Holes? • The amount of mass of a black hole is huge so it drags stuff into it gravitationally • A good analogy would be crumbs on the surface of the water as it goes down the sink: swirling faster and faster as it reaches the drain and gets sucked down. • As the matter moves more quickly you can get violent collisions and we can see this light… Picture on page 220. Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 151 BHOT 8 cont… • He begins transmitting at 2 seconds before 11:00 • Gravity slows time, so the stronger the gravity the greater the effect • What is one second to the astronaut will be more than one second to the spaceship Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 152 • However, they will never see the one from 11:00 • The light will get “redder” and redder • Figure on page 81 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 153