Stellar Evolution and the HertzsprungRussell Diagram 7/14/09. Astronomy 101

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1 Stellar Evolution and the HertzsprungRussell Diagram 7/14/09 Astronomy 101

2 Astronomy Picture of the Day Astronomy 101

3 Outline for Today Astronomy Picture of the Day News Articles Business Return Lab 5 Q&A session The Sun Hertzsprung-Russell Diagrams The Lives of Low-Mass Stars The Lives of High-Mass Stars Minute Writing Break Lab 7 Astronomy 101

4 (About the Sun)

5 Solar Activity

6

7

8 Movie

9

10

11 Different Types of Stars Different Masses Different Temperatures Different Sizes Same Stuff, (mostly the) Same Science Hydrogen and Helium and a bit of everything else Hot incandescent Gas Nuclear Furnace Gravitational Equilibrium Astronomy 101 with Pressure

12 Different Types of Stars Oh Be A Fine Guy/Girl, Kiss Me Astronomy 101 (The Sun)

13 HOT The spectral sequence in order COOL

14 Luminosity/Absolute Magnitude Hertzsprung-Russell (H-R) Diagram Temperature/Color

15 Why are Luminosity these cold, red stars brighter? Why are these hot, blue stars fainter? Temperature

16 C Luminosity B Which star has the largest radius? D A Astronomy 101 Temperature

17 Main Sequence High-mass stars Hydrogen to Helium Burning in core 90% of the star's life Where the Sun is Low-mass stars

18 Massive Main Sequence Stars Larger gravitational forces balanced by higher central pressures 18

19 Suppose the mass of a star increases The Central Pressure: A) Decreases B) Increases The Central Density: A) Drops B) Increases 19

20 Suppose the mass of a star increases The Central Pressure: A) Decreases B) Increases The Central Density: A) Drops B) Increases 20

21 Suppose the Central Pressure and Density Increase The Central Temperature: A) Decreases B) Increases 21

22 Suppose the Central Pressure and Density Increase The Central Temperature: A) Decreases B) Increases 22

23 Suppose the Central Temperature Increases The Rate of Fusion A) Decreases B) Increases 23

24 Suppose the Central Temperature Increases The Rate of Fusion A) Decreases B) Increases 24

25 Mass PressureTemperatureFusion Higher central temperatures lead to higher temperatures throughout the star The also lead to higher fusion rates 25

26 The Lifetime of a star is extremely sensitive to its mass. Massive stars have more Hydrogen to burn BUT Massive stars burn their Hydrogen more quickly Add picture of hybrid vs SUV 26

27 Live Fast, Die Young! Sun (1MX, 1L ) 1010 years to use up its Hydrogen. Low mass stars live FOREVER!!! Heavy Star (10M, ~10,000L ) 107 years High mass stars die IMMEDIATELY! 27

28 Live Fast, Die Young! c Sun (1M, 1L ) 1010 years to use up its Hydrogen. Low mass stars live FOREVER!!! Heavy Star (10M, ~10,000L ) 107 years High mass stars die IMMEDIATELY! 28

29 Log(number) More Low Mass Stars Than High Mass Stars c Log(mass) 29

30 Main Sequence High-mass stars Low-mass stars

31 Luminosity A D B C Astronomy 101 Temperature Which of these stars can be no more than 10 million years old?

32 Luminosity A D B C Astronomy 101 Temperature Which of these stars will have changed the least 10 billion years from now?

33 Luminosity A D B C Astronomy 101 Temperature Which of these stars will we see the most of if we look at the volume of space near us?

34 Luminosity A D B C Astronomy 101 Temperature Which of these stars are we most likely to see far away from us?

35 Bunches of stars can form together in clusters They all reach the main sequenc 35

36 The high mass stars are gone! After time passes Only long-lived low mass stars are left! 36

37 What Happens When A Star Stops Being on the Main Sequence? Star runs out of Hydrogen in the core Core collapses Then what? Depends on Mass High Mass Stars > 8 MSun Intermediate Mass Stars Low Mass Stars < 2 MSun Brown Dwarfs 37

38 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 38

39 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 39

40 Rules for the Day When Stuff gets hotter and denser, heavier elements can fuse together. Heavier elements have more nuclear charge, and thus more repulsion! Takes more energy to force them together. 40

41 Happy Star on the Main Sequence. Nice Hot Dense region with lots-o-hydrogen to burn. La la la la Becomes 41

42 Nervous Star ending its time on the Main Sequence. Running out of Hydrogen! Energy output is going down! Um errr 42

43 Nervous Star ending its time on the Main Sequence. Without fusion, the temperature of the core will: Um errr A) Cool down B) Heat up 43

44 Nervous Star ending its time on the Main Sequence. Without fusion, the temperature of the core will: Um errr A) Cool down B) Heat up 44

45 Nervous Star ending its time on the Main Sequence. The pressure in the core will: Um errr A) Decrease B) Increase The core will: A) Shrink B) Expand 45

46 Nervous Star ending its time on the Main Sequence. The pressure in the core will: Um errr A) Decrease B) Increase The core will: A) Shrink B) Expand 46

47 Core shrinks because it cools! Fusion Stops! Core Cools! Pressure Drops! Temperature Pressure Core Shrinks! 47

48 Nervous Star ending its time on the Main Sequence. As the core starts to shrink and material falls in: Temperature will: A) Keep cooling down B) Start heating back up Density will: A) Decrease B) Increase 48

49 Nervous Star ending its time on the Main Sequence. As the core starts to shrink and material falls in: Temperature will: A) Keep cooling down B) Start heating back up Density will: A) Decrease B) Increase 49

50 Nervous Star ending its time on the Main Sequence. It shrinks, and heats up! Layers above it fall in too! (nothing is pushing back) 50

51 Nervous Star ending its time on the Main Sequence. Collapsing layers have hydrogen and are now dense enough for hydrogen fusion Shell is now even denser & hotter than original core! Shell Burning Huge energy output! Huge LUMINOSITY! 51

52 Nervous Star ending its time on the Main Sequence. Luminous shell pushes up the stuff above it. Core is still collapsing through! 52

53 The star gets redder when it swells up! hotter gas expands and cools cooler This turns the main sequence star into a red giant! 53

54 Helium core, Hydrogen burning shell. Before After 54

55 55

56 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 56

57 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 57

58 The inert Helium in the core ignites in a Helium Flash For massive enough stars Pressure, density and temperature increase in the collapsing core until the Helium is able to undergo fusion! Burning Inert Burning Burning! 58

59 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 59

60 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 60

61 Eventually, Helium Also Runs Out Stars like the Sun stop fusion here Note that there are now two shells! Extra luminous! 61

62 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 62

63 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 63

64 As the Star Expands, What Happens to the Gravity Holding on to the Outer Layers of the Star? A) Stays the same because the star's mass is the same B) Increases because the star is bigger C) Decreases because the mass is smaller from fusion D) Decreases because the radius of the star is larger 64

65 As the Star Expands, What Happens to the Gravity Holding on to the Outer Layers of the Star? A) Stays the same because the star's mass is the same B) Increases because the star is bigger C) Decreases because the mass is smaller from fusion D) Decreases because the radius of the star is larger 65

66 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 66

67 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 67

68 68

69 69

70 70

71 71

72 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 72

73 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 73

74 The evolutionary track of a 1M star Fades Cools 74

75 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 75

76 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 76

77 Fusion in High Mass Stars Once Hydrogen in the core runs out, Hydrogen fusion in the envelope, Helium fusion in the core Once Helium in the core runs out, Hydrogen & Helium fusion in the envelope, Carbon fusion in the core And so on... 77

78 78

79 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 79

80 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 80

81 Like all desperate measures, each fix is less successful than the first Temperatures are hotter and hotter Burn rate is faster and faster But less and less energy released per atom fused H-burning: 7 million years (107 K) He-burning: 500,000 years (109 K) C-burning: 600 years Ne-burning: 1 year O-burning: 6 months Si-burning: 1 day! (1011 K) (1012 K) (1013 K) (1014 K) 81

82 Ends When Not Hot Enough to Fuse Next Element OR at Iron 82

83 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 83

84 Hydrogen Fusion Core Collapse, Hydrogen Shell Burning Helium Core Burning, Hydrogen Shell Burning Onion Layer Shell BUrning Hydrogen and Helium Shell Burning, Carbon Core Outer layers Ejected Planetary Nebula White Dwarf Iron Core Supernova (type II) Neutron Star Black Holes 84

85 Minute Writing What concept do you feel most confident on? What do you feel least confident on? Astronomy 101

86 Assignments Read Chapters 18; Send Jeff and me two questions by Thursday Read Lab 8; Send Jeff and me one question by Thursday Lab 7 due Thursday No News Article Due Next Tuesday!(study, instead) Astronomy 101

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