Big Bang, Black Holes, No Math

Transcription

1 ASTR/PHYS 109 Dr. David Toback Lecture 33 1

2 Was due Today L33 Reading: (Unit 5) Pre-Lecture Reading Questions (PLRQ) Unit 5 Revision (if desired): Was due today before class End-of-Chapter Quizzes: Chapter 15 Papers Paper 3: Grades with curve posted. Let us know if you were misgraded Paper 3 Revision (if desired): Due Friday in TurnItIn General: Mis-graded on any Assignment? Let us know 2

3 Unit 5: Big Objects 1. Galaxies 2. Star Birth and Death Today 3. More on Black Holes It turns out that the way Galaxies and Stars form is very similar start there The way stars die depends on the star itself sometimes they die to form a Black Hole 3

4 Important Buzz Words Wanted to make sure we explained some of the important buzz words in astronomy: Red Giant Supernova White Dwarf Neutron Star Black Hole 4

5 Today s Lecture A star is born Nuclear reactions and gravity keep stars alive and make them shine The life of stars: shining and converting hydrogen into heavier elements Life and death of stars like our Sun Life and death of massive stars 5

6 Where are we now in the history? A few hundred million years after the bang, stars start forming 6

7 Quick Summary of Galaxy Formation Half a million years after the Big Bang we have lots of neutral stuff floating around in space Half a billion years after the bang the stuff has clumped into galaxies 7

8 Stellar Clumps The galaxies start as giant spinning areas of neutral, massive stuff kept together by gravity Eventually, local areas that orbit around the center of the galaxy are close enough to each other that atoms can start clumping into stars due to gravity Dark matter just whips on through so it doesn t clump into stars like the atoms Eventually, the hydrogen and helium atoms can start to interact with each other 8

9 Star Formation This is some text.. 9

10 Step 2 More Can think of the atoms going around as each being a racecar going around the track 10

11 Step 3 This is some text Beginnings of planets! The racecars that keep going around attract each other via gravity (not very racecar like), so they can clump and form planets 11

12 Stars have some things in common with Spiral Galaxies Will be the planets Will be the star Gee kinda looks like Saturn also 12

13 Describing Stars We tend to use metaphors to describe Stars 1. Can think of them like people: They have a birth, a life and a death 2. Can think of them like a car: They run on fuel, and die when they run out of fuel 3. Can think of them like a balloon: A giant collection of atoms that are forced to stay inside the balloon walls 13

14 Proto-stars Gravity brings together the stuff in a galaxy that has mass When the atoms (mostly hydrogen and a little helium) get close enough they start falling towards the center and pick up speed However, need to get really close before they will interact 14

15 Low energy (temperature) hydrogen reactions Proton Proton=Hydrogen Electro-magnitism Reaction Same charges repel Proton 15

16 A Star is Born When there are enough atoms, the large amount of mass makes the pull so strong that the hydrogen is moving very quickly by the time it gets to the center become higher temperature/energy When hydrogen nuclei reach a high enough energy (10 Million Kelvin) they start to have nuclear interactions Creates the light we see (makes stars shine) Atoms inside the Sun don t move in the same way the Earth orbits outside it Call this a star 16

17 Proton Hydrogen Reactions at high Proton=Hydrogen Temperatures Proton + Proton Deuterium + Electron + Neutrino Nuclear Reaction Anti-Electron Deuterium Proton Neutrino This is what we call Fusion Out-going particles get LOTS of energy 17

18 The Life and Death of Stars A star s life is effectively a battle between: 1.Gravity trying to crush everything into a tiny point 2.The nuclear interactions opposing the gravity 18

19 Only in the center of Stars The center of a star is called the core This is where the particles have the highest energy and density This is where all the fusion occurs 19

20 Where does the energy come from? Mass of Deuterium is smaller than the mass of two protons So what? E=mc 2, so the mass energy gets converted into kinetic energy in the collision (and light) 20

21 Hydrogen Reactions Proton Proton + Proton Deuterium + Electron + Neutrino Proton=Hydrogen Nuclear Reaction Anti-Electron Deuterium Proton Neutrino Fusion produces particles with LOTS of energy 21

22 Hydrogen and Deuterium Deuterium Proton + Deuterium 3 He + Photon Again, lots of energy to the particles Nuclear Reaction Photon 3 He Proton 22

23 Creating Stable Helium 3 He 3 He + 3 He 4 He + 2 Hydrogens Even more energy is released Nuclear Reaction Hydrogen 4 He 3 He Hydrogen 23

24 Nuclear Burning In each nuclear reaction additional energy is released Some of the energy turns into photons (and neutrinos) This is what makes stars shine Some energy goes into the increased speed of the atoms This is what keeps the star from crushing itself How? 24

25 Thinking of a Star as a Balloon The hydrogen and helium are the gas inside the balloon, the fusion speeds them up so they try to leave The gravity is what keeps it all together, like the Hydrogen and Helium gas Gravity holds it together walls of the balloon 25

26 For Next Time L33 Reading: (Unit 5) Pre-Lecture Reading Questions (PLRQ) Unit 5 Revision (if desired): Was due today before class End-of-Chapter Quizzes: Chapter 16 (if we finished Chapter 16, else just 15) Papers Paper 3: Grades with curve posted. Let us know if you were misgraded Paper 3 Revision (if desired): Due Friday in TurnItIn General: Mis-graded on any Assignment? Let us know 56

27 Full set of Readings So Far Required: BBBHNM: Chaps Recommended: TFTM: Chaps. 1-5 BHOT: Chaps. 1-7, 8 (68-85), 9 and 11 ( ) SHU: Chaps. 1-3, 4(77-93), 5(95-114), 6, 7 (up-to-page 159) TOE: Chaps