Supernova Neutron Star Planetary Nebula

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

Atomic Addition – I. Prelude Key

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

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)

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

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

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.

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:

II. Big Bang Nucleosynthesis 1H1 + 0n1 → 1H2 + 0γ0 1H2 + 1H2 → 2He3 + 0n1 + 0γ0 2H3 + 1H2 → 2He4 + 1H1 + 0γ0

II. Big Bang Nucleosynthesis 1He3 + 2He4 → 3Li7 + 0γ0 (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.  

II. The “Be Bottleneck” 4 Be 7 and 4 Be 8 form, but fall apart right away: 2He3 + 2He4 → 4Be7 + 0γ0 4Be7 + -1e0 → 3Li7 ( 4Be7 turns into 3Li7 by electron capture. ) 2He4 + 2He4 → 4Be8 + 0γ0 4Be8 + 0γ0 → 2He4 + 2He4 4Be8 is unstable – it immediately* turns back into 2 2He4 ( *after just 10 -17 sec ).

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?

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

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

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

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:

Hydrogen Fusion – 40 Million oC ( +1β0 )

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

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

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

Hydrogen Fusion Deuteron Proton “Light” Helium Gamma Ray

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

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

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.)

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

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 ): 6C12 + 1 H1 → 7 N 13 + 0 γ 0 unstable 7N13 → 6C13 + +1 β 0 + ν 6C13 + 1 H1 → 7 N 14 + 0 γ 0 stable

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 14 + 1 H1 → 8 O 15 + 0 γ 0 unstable 8 O 15 → 7 N 15 + +1 β 0 + 0 ν 0 7 N 15 + 1 H1 → 8 O 16 + 0 γ 0 stable

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.

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.

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

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…

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

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

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

Helium Fusion – Red Giant Core

Helium Fusion – Red Giant Core

Helium Fusion – Red Giant Core

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

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.

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.

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

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.

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…

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…

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

Alpha Process Nucleosynthesis in Supergiants

Alpha Process in Supergiants

Alpha Process in Supergiants (aka “Helium Capture”)

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

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.

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.

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.

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

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.

Neutron Capture Process

Neutron Capture Process Key Neutron Capture Beta Decay

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

Neutron Capture Process Beta decay

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

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 (0.000005 sec)!

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

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

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

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

Young Supernova Remnant Cloud and Neutron Star

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

Neutron Star Cutaway

Neutron Star

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