Supernovae & Nucleosynthesis 1.What are supernovae? What the different kinds of supernovae? 2.What is nucleosynthesis? What does it happen? Supernovae: two main types Type II – massive stars Type Ia – explosion of white dwarf in binary systems) Also, Type Ib – massive stars but no H envelope Type Ic – massive stars but no H/He envelope Type II SN: core collapses into a neutron star, blows off envelope 8–25 Msun: NS 25–100 Msun: BH Type Ia occurs in binaries when companion transfers mass to WD Type Ibc: happens in massive stars sans H/He envelope Light curves of SN: Ia vs. II When does nucleosynthesis happen? Stellar nucleosynthesis 2. Main Seq. 3. Red Giant low mass high mass star (< 5 M ) 1 & 5. star (>5 M ) sun molecular sun high mass cloud star (>5 M ) 4. Planetary nebula sun 5. Neutron star 4. Supernova 4. White dwarf Nucleosynthesis possible 5. Black hole if white dwarf in binary system (during nova or supernova) The proton-proton chain is the staple of main-sequence dwarfs Hydrogen Deuterium Helium Occurs in stars > 0.08 Msun Higher-mass stars fuse H via the CNO cycle Occurs in stars > 1.1 Msun Helium fuses mainly via the triple-alpha process Occurs in stars > 0.5 Msun Elements heavier than Carbon form via He-capture Occurs in stars > 5 Msun Other fusion reactions can occur as well Where are different elements produced? Q: How do we know nuclear fusion is happening in stars? Review: Supernovae & Nucleosynthesis When does nucleosynthesis happen? Stellar nucleosynthesis 2. Main Seq. 3. Red Giant low mass high mass star (< 5 M ) 1 & 5. star (>5 M ) sun molecular sun high mass cloud star (>5 M ) 4. Planetary nebula sun 5. Neutron star 4. Supernova 4. White dwarf Nucleosynthesis possible 5. Black hole if white dwarf in binary system (during nova or supernova) Nucleosynthesis Nucleosynthesis happens when nucleons combine to produce energy 4 H —> He (p-p chain) is the staple of solar-type stars Heavier stars burn hydrogen with the CNO cycle He fuses to C Heavier elements are produced by capturing He Iron is the heaviest element produced by fusion Heavier elements are produced by neutron capture or decay.