Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 20 & 21

1. Big Bang, Black Holes, No MathASTR/PHYS 109Dr. David TobackLecture 20 & 21

2. Was due Today – L20 • Reading: • Unit 5 • Pre-Lecture Reading Questions: • Unit 4 Revision (if Desired): Stage 2 • Unit 5: Stage 1 • End-of-Chapter Quizzes: • Chapter 14 • Papers: • Paper 2 Revision (if desired): • Stage 2 due Wednesday before class • Paper 3: • Stage 2 due Wednesday before class

3. Was due Today – L21 • Reading: • Unit 5 • Pre-Lecture Reading Questions: • Unit 5: Stage 2 • End-of-Chapter Quizzes: • Chapter 14 • Papers: • Paper 2 Revision (if desired): • Stage 2 • Paper 3: • Stage 2

4. Quick Review: Various Times Walking through what happens during each of a number of different periods in time • The VERY early universe • The first three Minutes • The next 300,000 years • The next billion years • ~13 billion years later (now) • The ultimate fate of the universe? } Chap 13 } Chap 14 } Chaps 15-17 } Unit 6

5. Unit 5 Overview • It turns out that the way Galaxies and Stars form is have similarities… start there • The way stars die depends on the star itself… sometimes they die to form a Black Hole • Black Holes are some of the weirdest things in the Universe… • In many ways the formation of Black Holes is like the Big Bang in Reverse

6. Unit 5: Big Objects and Black Holes • Galaxies • Star Birth and Death • Black Hole Formation • Properties of Black Holes Today

7. Galaxy Formation: Overview • Big picture: What Galaxies “look like” • A gravity dominated Universe allows galaxies to form • Stars in Galaxies • When do galaxies form?

8. What do galaxies look like? All have common properties • Stars (produce the light we see) • Gas (atoms not in stars) • Dark Matter (most of the mass)

9. Visualizing a Galaxy • The light comes from the stars • Most of the mass is Dark Matter In some ways, Dark Matter surrounds the galaxy like the water in a fishbowl surrounds a fish in the middle of the bowl. Not exactly the same… denser in the middle because of the pull of gravity

10. Two examples of Galaxies Spiral Galaxy like the Milky Way • Bulge in the middle • Disk on the sides Elliptical Galaxy • One giant bulge, stars are like bees buzzing around the center, biggest galaxies are spirals

11. From the Early Universe to Galaxies • After about ~3 minutes things are cool enough for nuclei to form • After ~300,000 years things are cool enough for electrons and nuclei combine to form atoms • Let’s move to a half a billion years after the bang

12. Where are we now in the history? Half a billion years after the bang

13. A Gravity Dominated Universe • The gravitational attraction between massive things ONLY makes them move towards each other through space • Dark Matter and atoms are neutral and massive • Both are most attracted to the closest place with lots of mass

14. Wait a Half Billion Years • As the years go by, mass clumps together • By a half a billion years after the bang, most of the mass is in one of a large number of “clumps” • Huge numbers of these clumps, each helps form galaxies!

15. Galaxy Creation 0

16. Galaxy Formation Analogy:People Jumping on a Trampoline If two people touch, then will stick together If they fall they create a big dent in the trampoline (like a dent in space-time) Once you get that first dent on the trampoline everyone starts falling into it

17. More Analogies • Water being poured into a bowl and flowing to the bottom • Water swirling in a bowl • Water in a bathtub with the drain open (and ignoring what happens to the water that goes down the drain)

18. Water Flowing • Think about water moving towards a drain in the bathtub • All falls in quickly  can get bubbling at the drain • Falls in slowly  Get swirling • Different types of galaxies can form

19. Stars in Galaxies • Atoms fall towards the center of the galaxy • Stars form where there are lots of atoms • Once the atoms form stars there is a large amount of distance between stars • About 4 light years between us and our nearest neighbor star • A good exception is binary stars where two stars formed together • Stars can orbit around the center of the galaxy

20. Slow Atoms Outside the Galaxy Where does the disk of the Milky Way come from? Lots of atoms moving around, far outside the center of the galaxy

21. Spinning into Shape • Gravity attracts mass to the densest place • Center of the Galaxy • As the mass is pulled in, it starts moving slightly around the center • Why does this happen?

22. Analogy: Ice Skater Matter far away from the center Spins slowly • You’ve seen on TV • Try this at home in a chair that rotates • Get yourself spinning with your arms and legs stretched out, then pull them in Pull the Matter in  Spins faster Can also think about water falling into a toilet after it’s flushed For those of you who have taken PHYS 218, this is Conservation of Angular Momentum

23. Dark Matter Vs. Atoms • Dark Matter and Atoms behave differently in galaxies • When atoms get near each other they can bump into each other like people moving in a movie theater • Dark Matter is more like two ships passing in the night

24. Why is there a disk on the outside? • Focus on the atoms in the outer part of the galaxy… Not very dense out there, so stars don’t form quickly • As atoms fall toward the center they are like the water from the outer part of a toilet bowl • They start bumping into other atoms, bounce in some other direction • Once enough atoms are going in different directions a swirl CAN start; atoms moving WITH the swirl can keep moving nicely and can go into a circular orbit like a planet around the sun • Like in a toilet, an effective swirl can continue • Atoms that try to go into other directions bang into the swirl and lose energy • Eventually, all the atoms have either fallen in or become part of the swirl • Eventually, the cloud gets drawn in close enough that the atoms get close enough that they form stars • Stars just stay in the disk orbit • Call this the disk

25. Visualize the process Start right after things start to contract…

26. Time progresses As the galaxy contracts, things can start moving very quickly

27. More time Passes Things start to flatten out…

28. More time…

29. Even more time…

30. Even more time..

31. Stable Galaxies The stuff in this stable state forms Stars: Call this a Galaxy • Can give us disk-like rotating galaxies • Can also form other types like elliptical galaxies • Galaxies often collide and get even more complicated

32. Fun video • Move from the simple view of a galaxy forming to a more complete computer model from NASA • How a disk galaxies gets created https://www.youtube.com/watch?&v=_Ssc1GsqHds

33. Another fun video Andromeda tied to the rocks Simulation of Andromeda colliding with the Milky Way, showing the creation of a combined galaxy http://people.physics.tamu.edu/toback/109/Video/andromeda.avi

34. Move from what galaxies look like to WHEN galaxies form in the history of the Universe

35. When? • Oldest observed galaxies appear about 500 million years after the bang • Do we understand why this is? Use computer simulations to see when, after the Big Bang, galaxies form • It turns out that if the Universe had exactly the same temperature everywhere it would take more than a hundred billion years to get even one galaxy • What????

36. Reason things might clump earlier? • Clearly galaxies DID form before that, so SOMETHING must have caused them to start earlier • Example of possible answer: If the temperature weren’t perfectly uniform then we could get clumping earlier • Go back to our trampoline analogy

37. Kids on a Trampoline The galaxies form shortly after we get that first big dent in space time • If we start with all the kids equally spaced, then it will take longer to get that first collision • If two of the kids happen to start slightly nearer each other, then those two are more likely to get a collision sooner and create the first dent sooner

38. Quantum Mechanics • It turns out that when the Universe is really small, the effects of Quantum Mechanics can have a big effect on the smoothness of the Universe • Can cause small variations in the temperature at different places in space • Scientists gave this a cool name: Quantum fluctuations

39. So What? • Different Temperature  Variation in the amount of matter in different places • A region with slightly more matter is more likely to be the place where matter clumps • Thus, Quantum Fluctuations in the Early Universe could cause Galaxy formation to occur earlier in time

40. How would we look for this? • How do we look at the temperature in the Universe? • Study the Cosmic Background Radiation temperature distribution • Any variations in different directions?

41. Look for Variation in the Cosmic Background Radiation Look at the full sky in a single map Stretch out a sphere onto a flat page Temperature Map (i.e, different colors correspond to different temperatures) Incredibly Uniform, but are there small variations?

42. Exactly the same everywhere? • Subtract off the same amount everywhere • What are we left with? The overall temperature is 2.728 degrees Kelvin The variation is very small DT = 3.353 mK

43. Hotter and Colder? Colder here? Hotter here? DT = 3.353 mK

44. What if we’re moving?

45. Better Explanation Doppler effect of our speed relative to the rest frame of the photon background Earth is going around the sun at ~30 km/sec and the solar system is moving around the Milky Way at ~250 km/sec Moving away from this direction Moving toward this direction

46. The Cosmic Background Radiation 0 Subtract off all the known effects and look for “Variations” Lots of small fluctuations (Spots) Everywhere Combining Quantum Mechanics and General Relativity predict where the galaxies form AND how long it takes

47. For Next Time – L20 • Reading: • Unit 5 (already due) • Pre-Lecture Reading Questions: • Unit 5: Stage 2 due Wed before class • End-of-Chapter Quizzes: • Chapter 15 (if we finished Chapter 15, else just 14) • Papers: • Paper 2 Revision (if desired): • Stage 2 due Wednesday before class • Paper 3: • Stage 2 due Wednesday before class

48. Full set of Readings So Far • Required: • BBBHNM: Chaps. 1-16 • Recommended: • 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) • TOE: Chaps. 1-3

49. End of Lecture

50. Dark Matter in Galaxies Finished looking at the things that produce light we can see in a Galaxy Move to the parts which have most of the mass Since Dark Matter doesn’t interact much, expect it to engulf the Galaxy