Big Bang Black Holes No Math ASTRPHYS 109
Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lectures 26 & 27 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 1
Rest of the Semester-L 27 Date Lecture number Due Before class/11: 55 PM What we do in Class Assigned after class Mon Nov 22 nd 25 EOC 14 (A-D) Chapter 16 EOC 14 (E-G) Wed Nov 24 th (Reading Day, No Class) Mon Nov 29 th 26 EOC 14 (E-G) (if not done already) Finish Chapter 16 + Most of Chapter 17 EOC 15 & 16, Paper 4 Text & Reviews, Unit 6 Reading Wed Dec 1 st 27 EOC 15 & 16, Unit 6 Reading Finish 17, Chapter 18 + Chapter 19 EOC 17 & 18, Unit 6 PLRQ Quiz Mon Dec 6 th (Redefined day, No class) EOC 17 & 18, Unit 6 Quiz - - Wed Dec 8 th 28 (Last day of class) Paper 4 Text & Reviews Chapter 19 + Chapter 20 Chapter EOC 19, AMS II and EOC 20 Mon Dec 13 th No Final EOC 19, AMS II and EOC 20, Paper 4 Feedback and any Revisions must be completed by today - - Notes: • Mis-graded on any Assignment? Let us know • Will start calculating grades on Mon Dec 13 th Honors Section: • Stage 4, Final Draft due Mon Nov 29 th • Stage 5, First Draft due Mon Dec 6 th • Stage 5, Final Draft due Wed Dec 8 th Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 2
Reminder About Grades • From Syllabus Since almost everyone is in the penalty, the Advisory Grade is currently the lowest of the four averages so you know how to make sure you get the grade you want You make keep doing revisions until grades are posted Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 3
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 4
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 5
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 as usual Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 6
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 7 Bang Topic 3: Properties of Black Holes, No Math
Moving Towards Black Holes • If a neutron star has a “critical mass” (about 3 MSun) 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 8
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 9
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, nonshining, 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 10
What it IS: A small, massive THING in Space • Shrink Sun to 10% of its size • Shrink to 1% • Neutron star is 0. 004% of the~25 Kilometers caecrosy)s a it sp lar original size in ngu t in Si o a p d e l • What if it were. Sing calle en t crushed into a (of black hole? 1. 4 Million Kilometers across Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 11
Most people have seen the curved Space-Time figure, so let’s understand those! The size of the Sun… Big Bang, Black Holes, No Math Remember: Diagram shows the CURVATURE of Space-time Draw the dent to be deepest is where the force is largest Where space is falling to the center “fastest” Big Objects and Black Holes. Nothing to “See” 12 Topic 3: Properties of Black Holes
How the Curvature Changes as we Compress the Sun What if we compressed the Sun into a Neutron Star? Far outside the Sun you can’t really tell the difference • Force is the same You can tell the difference if you are very close to the Sun itself • Force is bigger The sun is now a few kilometers across Big Objects and Black Holes Big Bang, Black Topic 3: Properties of Black Holes, No Math 13
Compress the Sun into a Black Hole Remember: The black hole is just a point in space Infinite curvature Big Bang, Black Holes, No Math Curvature is VERY different really close to where the mass is Nothing “curved” to SEE, deeper just means where space falling in fastest Only showing 2 dimensions Big Objects and Black Holes Topic 3: Properties of Black Holes 14
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 • Wouldn’t suck in any more stuff than the sun does • Then again, without the light it would get really cold and we’d all die… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 15
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 16
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 http: //people. physics. tamu. edu/toback/119/lab/Lab 3/Part. I/Earth_P 2. html Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 17
The Moon has a “small” escape Velocity Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 18
The Escape Velocity for the Earth Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 19
The Sun Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 20
A Neutron Star Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 21
A Black Hole Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 22
Event Horizon • A rocket with a speed of 11 km/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 EVENTBig. HORIZON Objects and Black Holes Big Bang, Black 23 Holes, No Math Topic 3: Properties of Black Holes
A Star with ~3 times the mass of the Sun is crushed into black hole Event Horizon Star gets crushed by gravity and becomes a single point in space/black hole (X marks the spot) ~20 km from black hole: Speed needed to escape is less than the speed of light (can escape) X ~5 km from black hole: Speed needed to escape from black hole this close is twice the speed of light (light can’t escape) ~10 km from black hole: Speed needed to escape is EXACTLY the speed of light This distance from the black hole is known as the event Horizon X X X Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 24
Event Horizon Cont… • The bigger the mass of the black hole, the further out the event horizon is http: //people. physics. tamu. edu/toback/119/lab/Lab 3/Part. II/BHS 1. html Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 25
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 can’t escape! Looks at this from the perspective of Space-Time Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 26
Space-Time as an Escalator Space falls towards the massive object, carrying objects along with it People can walk THROUGH space away from the massive object Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 27
Falling into a Black Hole If a person moves “up” slower than the “speed of the escalator” she will fall towards the object A person moving through space away from a black hole actually gets closer to the black hole over time 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 28
Space-Time Near a Black Hole • If light can’t escape from a star, then we can’t “see” light coming 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 29
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 30
Gravitational Lensing of the light around a black hole Light from stuff orbiting it, and light from stars behind it Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 31
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 four 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 32
Some pictures from Chapter 2 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 33
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 only. Bigobserved in “distant” galaxies Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 34
Switch Topics • 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 35
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 36
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 37
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 38
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 39 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, No Math 40
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 41
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 42
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 43
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 44
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 45
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 46
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? What is the final theory of “Quantum Gravity”? String Theory? … Stay tuned… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 47
Lecture on Chapter 17 now complete Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 48
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 – Reviews should be done RIGHT after submission. Do Feedbacks as they become available Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 49
Rest of the Semester-L 26 Date Lecture number Due Before class/11: 55 PM What we do in Class Assigned after class Mon Nov 22 nd 25 EOC 14 (A-D) Chapter 16 EOC 14 (E-G) Wed Nov 24 th (Reading Day, No Class) Mon Nov 29 th 26 EOC 14 (E-G) (if not done already) Finish Chapter 16 + Most of Chapter 17 EOC 15 & 16, Paper 4 Text & Reviews, Unit 6 Reading Unit 6 PLRQ Quiz Wed Dec 1 st 27 EOC 15 & 16, Unit 6 Reading, Unit 6 Quiz Finish 17, Chapter 18 + Chapter 19 EOC 17 & 18 Mon Dec 6 th (Redefined day, No class) Paper 4 Text & Reviews - - Wed Dec 8 th 28 (Last day of class) EOC 17 & 18 Chapter 19 + Chapter 20 Chapter EOC 19, AMS II and EOC 20 Mon Dec 13 th No Final EOC 19, AMS II and EOC 20, Reviews, Feedback and any Revisions must be submitted by today - - Notes: • Mis-graded on any Assignment? Let us know • Will start calculating grades on Mon Dec 13 th Honors Section: • Stage 4, Final Draft due Mon Nov 29 th • Stage 5, First Draft due Mon Dec 6 th • Stage 5, Final Draft due Wed Dec 8 th Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 50
Rest of the Semester-L 27 Date Lecture number Due Before class/11: 55 PM What we do in Class Assigned after class Mon Nov 22 nd 25 EOC 14 (A-D) Chapter 16 EOC 14 (E-G) Wed Nov 24 th (Reading Day, No Class) Mon Nov 29 th 26 EOC 14 (E-G) (if not done already) Finish Chapter 16 + Most of Chapter 17 EOC 15 & 16, Paper 4 Text & Reviews, Unit 6 Reading Wed Dec 1 st 27 EOC 15 & 16, Unit 6 Reading Finish 17 EOC 17, Unit 6 PLRQ Quiz Mon Dec 6 th (Redefined day, No class) EOC 17, Unit 6 Quiz - - Wed Dec 8 th 28 (Last day of class) Paper 4 Text & Reviews Chapters 1820 Chapter EOC 18, 19, AMS II and EOC 20 Mon Dec 13 th No Final EOC 18, 19, AMS II and EOC 20, Paper 4 Feedback and any Revisions must be completed by today - - Notes: • Mis-graded on any Assignment? Let us know • Will start calculating grades on Mon Dec 13 th Honors Section: • Stage 4, Final Draft due Mon Nov 29 th • Stage 5, First Draft due Mon Dec 6 th • Stage 5, Final Draft due Wed Dec 8 th Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 51
Rest of the Semester-L 35 Date Lecture number Due Before class/11: 55 PM What we do in Class Assigned after class Fri Apr 16 th* 34 EOC 13 (A-F), EOC 14 (A-D) Chapters 16 EOC 14 (E-G) Mon Apr 19 th 35 EOC 14 (E-G) Finish Chapter 16 + Start Chapter 17 EOC 15, Unit 6 Reading Wed Apr 21 st 36 EOC 15, Unit 6 Reading Chapter 17 + Chapter 18 EOC 16 + 17, Paper 4 Assigned, Unit 6 PLRQ Quiz Fri Apr 23 rd 37 Unit 6 Quiz, EOC 16 + 17 Chapter 18 + Chapter 19 EOC 18 Mon Apr 26 th 38 EOC 18 Chapter 19 + Chapter 20 Chapter EOC 19, AMS II and EOC 20 Wed Apr 28 th 39 (Redefined day, Last day of Class) Paper 4 Text Due, EOC 19 Chapters 19 and 20 Chapter EOC 19, AMS II and EOC 20 Fri Apr 30 th No class AMS II and EOC 20, Reviews, Feedback and any Revisions must be submitted by today - - Tues May 4 th No Final All Reviews and Feedbacks due - - Notes: • Mis-graded on any Assignment? Let us know • Will start calculating grades on Tuesday May 4 th Honors Section: • Stage 4, Final Draft due Mon Apr 26 th • Stage 5, First Draft due Mon May 3 rd • Stage 5, Final Draft due Tuesday May 4 th Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 52
Rest of the Semester-L 36 Date Lecture number Due Before class/11: 55 PM What we do in Class Assigned after class Fri Apr 16 th* 34 EOC 13 (A-F), EOC 14 (A-D) Chapters 16 EOC 14 (E-G) Mon Apr 19 th 35 EOC 14 (E-G) Finish Chapter 16 + Start Chapter 17 EOC 15, Unit 6 Reading Wed Apr 21 st 36 EOC 15, Unit 6 Reading Chapter 17 EOC 16 + 17, Paper 4 Assigned, Unit 6 PLRQ Quiz Fri Apr 23 rd 37 Unit 6 Quiz, EOC 16 + 17 Chapter 18 + Chapter 19 EOC 18 Mon Apr 26 th 38 EOC 18 Chapter 19 + Chapter 20 Chapter EOC 19, AMS II and EOC 20 Wed Apr 28 th 39 (Redefined day, Last day of Class) Paper 4 Text Due, EOC 19 Chapters 19 and 20 Fri Apr 30 th No class AMS II and EOC 20, Reviews, Feedback and any Revisions must be submitted by today - - Tues May 4 th No Final All Reviews and Feedbacks due - - Notes: • Mis-graded on any Assignment? Let us know • Will start calculating grades on Tuesday May 4 th Honors Section: • Stage 4, Final Draft due Mon Apr 26 th • Stage 5, First Draft due Mon May 3 rd • Stage 5, Final Draft due Tuesday May 4 th Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 53
Rest of the Semester-L 2 X Date Lecture number (class number) Due Before class/11: 55 PM What we do in Class Assigned after class Wed Nov 11 th 25 EOC 14 (A-D) Chapter 16 EOC 14 (E-G) Mon Nov 16 th 26 EOC 14 (E-G), Rest of Chapter 16 + Chapter 17 EOC 15 & 16, Paper 4, Unit 6 Reading Wed Nov 18 th 27 EOC 15 & 16, Unit 6 Reading Chapter 18 EOC 17 & 18, Unit 6 PLRQ Quiz Mon Nov 23 rd 28 (Last day of Class) Paper 4 Text, Unit 6 Quiz Chapters 19 and 20 Chapter EOC 19, AMS II and EOC 20 Wed Nov 25 th Reading day, no class Mon Nov 30 th Reading day, no class EOC 17 & 18 Tues Dec 1 st No Final EOC 19, AMS II and EOC 20, Reviews, Feedback and any Revisions must be done by today Notes: • Mis-graded on any Assignment? Let us know • Will start calculating grades on Wed December 2 nd Honors Section: • Stage 3 due Wed Nov 18 th • Stage 4, Final Draft, due Monday Nov 23 rd Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 54
Rest of the Semester-LX Date Lecture number (class number) Due Before class/11: 55 PM What we do in Class Assigned after class Wed Nov 11 th 25 EOC 14 (A-D) Chapter 16 EOC 14 (E-G) Mon Nov 16 th 26 EOC 14 (E-G), Rest of Chap 16 + Part of Chap 17 EOC 15 & 16, Unit 6 Reading Wed Nov 18 th 27 EOC 15 & 16, Unit 6 Reading Rest of Chap 17 Paper 4, EOC 17, Unit 6 PLRQ Quiz Mon Nov 23 rd 28 (Last day of Class) Unit 6 Quiz Chapters 18 - 20 Chapter EOC 18, 19, AMS II and EOC 20 Wed Nov 25 th Reading day, no class EOC 17, Paper 4 Text (do your Reviews before Thanksgiving!) Mon Nov 30 th Reading day, no class Tues Dec 1 st No Final EOC 18, 19, AMS II and EOC 20, Reviews, Feedback and any Revisions must be done by today Notes: • Mis-graded on any Assignment? Let us know • Will start calculating grades on Wed December 2 nd Honors Section: • Stage 3 due Wed Nov 18 th • Stage 4, Final Draft, due Monday Nov 23 rd Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 55
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 21 st Century) Big Bang, Black 56 Big Objects and Black Holes Topic 3: Properties of Black Holes, No Math
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 57
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 58
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 59
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 60
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 basically the mass of the two black holes that started c) Black holes can’t collide Big Objects and Black Holes Big Bang, Black Holes, No Math Topic 3: Properties of Black Holes 61
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 62
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 63
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 64
Announcement before we begin Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 65
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 66
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/Cygnus. XR-1. mpg Holes, No Math Topic 3: Properties of Black Holes 67
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 68
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 69
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 70
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, No Math 71
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 72
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 73
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 74
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 75
Papers • Paper 1 is done • Paper 2 grades are on e. Learning – 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 76 Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes
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 77
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 78
Writing Assignments Short Assignments 1 & 2 Re-do’s are still possible. Want to revise again? Talk to me e. Learning: 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 79
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 Blackth Holes Big Bang, class, Black 80 Tuesday Dec 8 Topic 3: Properties of Black 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, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 81
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 82
Black Holes ain’t so black… Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 83
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 84
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 85
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=MC 2 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 86
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 87
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 88
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 89
http: //science. nasa. gov/headlines/images/blackhole-swirl. jpg Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 90
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 91
Schedule from Here on Out • Wed Nov 19 th: 25 th 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 24 th: 26 th lecture: Dark Energy • Wed Nov 26 th: No class – Research paper and 2 nd short paper due at midnight – Day before Thanksgiving. Class cancelled • Dec 1 st: No classes redefined day • Dec 3 rd: Reading period, no classes • Dec 8 th: Finals week, no final Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 92
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 93
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 94
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 95
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 96
Schedule from Here on Out • Mon Nov 17 th: 24 th lecture: Black Holes • Wed Nov 19 th: 25 th lecture: – Recitation for Paper 2 – Inflation • Mon Nov 24 th: 26 th lecture: Dark Energy • Wed Nov 26 th: No class – Research paper and 2 nd short paper due at midnight – Day before Thanksgiving. Class cancelled • Dec 1 st: No classes redefined day • Dec 3 rd: Reading period, no classes • Dec 8 th: Finals week, no final Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 97
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 98
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 Web. CT stuff Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 99
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 100
• 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 101
• 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 102
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 103
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=MC 2 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 104
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 105
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 106
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, p 54 Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 107
• 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 108
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 109
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 110
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 111
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 112
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 113
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 114
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 115
TOE 4 • Black holes ain’t so black. • Really want to talk about entropy and the 2 nd 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 116
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 117
• This is some text Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 118
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 119
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 120
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 121
• 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 122
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 123
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 124
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 125
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 126
• 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 127
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 128
Big Bang, Black Holes, No Math Big Objects and Black Holes Topic 3: Properties of Black Holes 129
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 130
• 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 131
• 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 132
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 8 MSun 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 133
• 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 134
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 135
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 136
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 137
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 138
• 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 139
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 140
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 141
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 142
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 143
• 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 144
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