1. Supernova
Neutron Star
Planetary Nebula

2. Stellar Nucleosynthesis and Supernova Nucleosynthesis
Add
+ ition
Atomic
Addition
Stellar Nucleosynthesis and Supernova Nucleosynthesis

3. Atomic Addition – I. Prelude
Key

5. Atomic Addition – I. Prelude
Nuclear Partial Reactions: These surprisingly strange reactions occur commonly as side reactions or as parts of more complex nuclear reactions:
0 n 1 = neutron 1 H 1 = proton
-1 e 0 = electron +1 β 0 = positron
0 ν 0 = neutrino 0 γ 0 = gamma rays

6. Atomic Addition – I. Prelude
The Three Isotopes of Hydrogen:
1 H 1 = Hydrogen (also symbol for 1 lone proton)
1 H 2 = Deuterium (1 proton and 1 neutron)
1 H 3 = Tritium (1 proton and 2 neutrons)

7. Atomic Addition – I. Prelude
Beta Decay – a neutron is converted to a proton by emitting an electron!!
0 n 1 → 1 H e ν 0
Electron Capture – a proton is converted to a neutron by capturing an electron!
1 H e 0 → 0 n ν 0

8. Atomic Addition – I. Prelude
Positron Emission – a proton is converted to a neutron by emitting a positron!
1 H 1 → 0 n β ν 0
Matter/Antimatter Annihilation - a positron and an electron annihilate each other to produce gamma ray energy.
+1 β e 0 → 0 γ 0

9. II. Big Bang Nucleosynthesis
In the first 10-4 (0.0001) sec, quarks combined to form protons (1H1) and neutrons (0n1).
Over the next minute or so, high energy photons collided to make electrons and neutrinos.

10. II. Big Bang Nucleosynthesis
Hydrogen, Helium and a trace of Lithium were the only elements created by the Big Bang.
H and He still make up 99.9 % of the universe today:

11. II. Big Bang Nucleosynthesis
1H n1 → 1H γ0
1H H2 → 2He n γ0
2H H2 → 2He H γ0

12. II. Big Bang Nucleosynthesis
1He He4 → 3Li γ0
(Just a trace of 3Li7
forms during the
Big Bang. (One 3 Li7
nucleus for every 8
billion 1He1 nuclei !)
1 H 3
3 Li 7
2 He 4
3 Li 7 decays with a ½ life of 12 years, so very little remains.  

13. II. The “Be Bottleneck”
4 Be 7 and 4 Be 8 form, but fall apart right away:
2He He4 → 4Be γ0
4Be e0 → 3Li7
( 4Be7 turns into 3Li7 by electron capture. )
2He He4 → 4Be γ0
4Be γ0 → 2He He4
4Be8 is unstable – it immediately* turns back into 2 2He4 ( *after just sec ).

14. Atomic Addition
Hydrogen, Helium and a tiny trace of Lithium were the only elements created by the Big Bang .
H and He still make up 99.9 % of the universe today.
However, Earth is loaded with heavier elements such as silicon, iron and oxygen.
How did all of these larger elements form?

15. Atomic Addition
The answer lies at the heart of the Stars :

16. Hydrogen Fusion – 40 Million oC
This is the thermonuclear reaction that powers main sequence stars like our Sun .

17. Hydrogen Fusion – 40 Million oC
High temperatures & pressures inside a star strip away electrons and overcome the electrostatic repulsion of protons.

18. Hydrogen Fusion – 40 Million oC
The strong nuclear force holds protons together once they’re pushed very close together by the high temperatures and pressures:

19. Hydrogen Fusion – 40 Million oC
( +1β0 )

20. 1H2 Hydrogen Fusion Proton Proton Deuteron (“Heavy” Hydrogen) Positron
Neutrino

21. Hydrogen fusion powers the Sun and
Proton-Proton Fusion
Hydrogen fusion powers the Sun and
Main Sequence Stars
Step 1: Two 1H  1 2H

22. Proton-Proton Fusion
Step 1: Positron annihilates an electron to make a gamma ray; neutrino flies off.

23. Hydrogen Fusion
Deuteron
Proton
“Light” Helium
Gamma Ray

24. Hydrogen fusion powers the Sun and
Proton-Proton Fusion
Hydrogen fusion powers the Sun and
Main Sequence Stars
Step 2: 2H + 1H  3He
Photon of light given off

25. Hydrogen Fusion “Light” Helium “Light” Helium Proton Helium Nucleus

26. Proton-Proton Fusion Hydrogen Fusion powers the Sun and
Main Sequence Stars
Step 3:
2 3He  4He + 2 1H
(2 protons fly off to create more fusion reactions.)

27. Proton-Proton Fusion:
Power Source of the
Main Sequence
Stars

28. IIIb. Carbon-Hydrogen Fusion
Nitrogen is produced in the sun by Carbon-Hydrogen Fusion:
occurs in small amounts in all stars
produces small amounts of Nitrogen and Oxygen:
6C12  7N13  6C13  7N14
6C12 nucleus fuses with 2 1 H1 nuclei, giving off a positron (+1 β 0 ):
6C H1 → 7 N γ 0 unstable
7N → 6C β 0 + ν
6C H1 → 7 N γ 0 stable

29. IIIb. Carbon-Hydrogen Fusion
Nitrogen is produced in the sun by Carbon-Hydrogen Fusion:
occurs in small amounts in all stars
produces small amounts of Nitrogen and Oxygen:
7N14  8O15  7N15  8O15
7N14 nucleus fuses with 2 1 H1 nuclei, giving off 1 positron (+1 β 0 ):
7 N H1 → 8 O γ 0 unstable
8 O → 7 N β ν 0
7 N H1 → 8 O γ 0 stable

30. Helium Fusion – 200 Million K Red Giant – White Dwarf Stage
When the sun runs low on Hydrogen in about another 5 billion years, gravity will take over and cause the core to collapse.

31. Helium Fusion – 200 Million K
This gravitational compression will cause the sun’s core to heat up to 200 million K and set off a whole new set of nuclear fusion reactions :
Helium
Fusion.

32. Helium Fusion – 200 Million oC Red Giant – White Dwarf Stage

33. Red Giants – Helium forms Carbon
Heat of He - C Fusion at the core of a red giant causes the outer H shell to flash off into space…

34. Inside a Red Giant Helium fuses to form Carbon and Oxygen at the Core
Extra heat causes outer shell of hydrogen
to fuse into He and billow out into space

35. Red Giants – Helium forms Carbon
…creating the Red Giant stage…

36. Red Giants – Helium forms Carbon
…that will engulf Mercury Venus, Earth and Mars and generally “toast” the rest of the solar system!! M V E M J S U V

37. Helium Fusion – Red Giant Core

38. Helium Fusion – Red Giant Core

39. Helium Fusion – Red Giant Core

40. Helium Fusion – 200 Million oC Red Giant – White Dwarf Stage
This will be the end of the line for our sun.
As the core of the red giant turns from Helium to Carbon, the sun will become a small, white-hot White Dwarf.
Sirius B

41. Helium Fusion – 200 Million oC Red Giant – White Dwarf Stage
As the nuclear reactions die out, the sun will become a Black Dwarf –
a huge cool ball of carbon –
a big black diamond
hanging unnoticed
in space.

42. End of the Line for Small Stars Like Our Sun
(Black Dwarf)
This will be the end of the line for our sun.
The carbon core of the black dwarf will collapse and heat up, but it will NOT heat up enough to trigger any new nuclear reactions.

43. End of the Line for Small Stars Like Our Sun – a Ball of Cold Carbon
Black Dwarf

44. Origin of the Elements Flow Chart
To review – All stars fuse H into He in their Main Sequence stage. All stars fuse He to make C in their Giant/Supergiant stage. Smaller stars like our Sun stop at this stage.

45. Red Supergiants – On Beyond Carbon
In larger stars ( > 8.0 M☉ ), the collapsing Carbon core raises temperature to 600 million K and a whole new round of reactions starts…

46. Origin of the Elements Flow Chart
In larger stars ( > 8.0 M☉ ), the collapsing Carbon core raises temperature to 600 million K and a whole new round of reactions starts…

47. Red Supergiants – On Beyond Carbon
Orion
Bellatrix – a Blue Giant
Betelgeuse - a Red Supergiant
Betelgeuse’s Future!
Rigel – Blue Supergiant

48. Alpha Process Nucleosynthesis
in Supergiants

49. Alpha Process in Supergiants

50. Alpha Process in Supergiants (aka “Helium Capture”)

51. Helium Capture (Alpha Process) in Supergiants
One 4He Nucleus at a time…

52. The End of the Line…
Iron (56Fe) acts like a nuclear “sponge”: it absorbs energy when it tries to fuse to make Zinc-60 (60Zn).
When enough Iron accumulates, the star goes out for the last time.

53. The End of the Line…
So, Fe is the largest element which can be produced inside a star.
All elements larger than 56Fe (and others) are formed during supernovas , when temperatures soar up to 8 billion oC.

54. Neutron Capture in Supernovas – You name it, you got it!!
8 Billion Degree Temperatures
Start a cascade of new elements to form and spread with the explosion.

55. Electron Capture Process
Incredible pressures at the star’s core shove electrons into each nucleus, where they combine with protons by electron capture to make trillions of neutrons:
1H1 + -1e0 → 0n1 + 0νe0

56. Neutron Capture Process
The high temperatures and pressures make possible a new “custom designer” process called Neutron Capture.
Any number of neutrons can be rapidly added to a nucleus.

57. Neutron Capture Process

58. Neutron Capture Process
Key
Neutron Capture
Beta Decay

59. Neutron Capture Process
If the nucleus becomes too unstable, one or more neutrons undergo beta decay to turn into protons to make the nucleus more stable:
0n1 → 1H1 + -1e0 + 0νe0

60. Neutron Capture Process
Beta decay

61. Neutron Capture Process
Any number of neutrons can be rapidly added to a nucleus:
Neutron capture - stable
Neutron capture - stable
Neutron capture - stable
Neutron capture - stable
Neutron capture - unstable
Beta decay - stable

62. Neutron Capture Process
This makes it possible to produce an element with any number of protons and neutrons, including rare radioactive elements such as Nobelium (No250), which has a ½-life of 5 millionths of a second ( sec)!

63. Supernova Remnant Cloud
Clouds
are loaded with new, rare exotic heavy elements
(Gold, Uranium, etc.)

64. Neutron Capture in Supernovas – You name it, you got it!!
Crab Supernova
Remnant
Cloud
(SRC) is loaded with rare, heavy elements.

65. Neutron Capture in Supernovas – You name it, you got it!!
SRC from Supernova 1987A

66. Neutron Capture in Supernovas – You name it, you got it!!
Evolution of Supernova 1987A and its SRC over the last 14 years

67. Young Supernova Remnant Cloud and Neutron Star

69. Silicon-Burning Alpha Process – Last 3 Days before Supernova+ 
4 2He  → 
32 16S
32 16S 
36 18Ar
36 18Ar 
40 20Ca
40 20Ca 
44 22Ti
44 22Ti 
48 24Cr
48 24Cr 
52 26Fe
52 26Fe 
56 28Ni
56 28Ni 
60 30Zn

70. Neutron Star
Cutaway

71. Neutron Star

72. Crab Supernova Remnant Cloud… …is loaded with these new elements