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Final Stages of Stellar Evolution for Take Away Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Final Stages of Stellar Evolution supernovae and the synthesis of heavy nuclei Benjamin Klein University of Karlsruhe 06.XII.2006 Seminar on Astroparticle Physics - Cosmic Rays Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Introduction What happens to stars which run out of fuel? What are supernova explosions and which different types exist? Where do heavy elements come from? Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Outline 1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements 2 Supernova Explosions White Dwarfs Classification of Supernovae 3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Outline 1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements 2 Supernova Explosions White Dwarfs Classification of Supernovae 3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Outline 1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements 2 Supernova Explosions White Dwarfs Classification of Supernovae 3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Outline 1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements 2 Supernova Explosions White Dwarfs Classification of Supernovae 3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Primordial Nucleosynthesis within the first 3 minutes after the Big Bang synthesis of light elements neutron/proton ratio of 1:7 most neutrons → He most remaining protons → H only traces of heavier elements nuclear magic numbers A = 5 and A = 8 photodissociation of heavier elements Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Stellar Nucleosynthesis synthesis of elements up to iron proton-proton chain CNO cycle nuclear burning in different zones onion structure Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Outline 1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements 2 Supernova Explosions White Dwarfs Classification of Supernovae 3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (1) process of neutron capture neutrons preferentially captured by heavy nuclei base material eg. iron nucleus becomes instable → β−-decay slow-process 5 11 neutrons “low” neutron flux (10 − 10 s·cm2 ) “low” temperatures (∼ 3, 000, 000K) β− decay before next neutron is captured conditions met in red giant stars Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (2) moving along the valley of stability Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (3) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (4) limitations of the s-process not all heavy elements can be synthesized in the s-process heavy nuclei, eg. thorium or uranium, decay several times before repeated neutron capture ends in bismuth cycle Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (5) Nuclear Astrophysics at FZK research group of Dr. Käpperle at FZK measurements of cross sections for neutron capture ratification of models for red giant stars Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away r-process (1) rapid-process 22 neutrons high neutron flux (∼ 10 cm2·s ) high temperatures multiple neutrons captured before β−-decay possible places where r-process could take place supernovae II (T ∼ 109K ) collision of two neutron stars abundance of r-process elements indicates that... only small quantity of supernovae returns elements to the outside every supernovae exposes only a small fraction of its synthesis products to the outside Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away r-process (2) processes slowing down the r-process heavy isotopes unstable because of spontaneous fission (A ' 270) → r-process ends neutron drip line → separation energy En = 0 closed neutron shells at N = 50, 82, 126 probability of capture sinks confirmation: higher abundance for this neutron numbers Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away r-process (3) magic neutron numbers: N = 82, N = 126 s-process: A = 138 (Barium) A = 208 (Lead) r-process: A = 130 (Cadmium) A = 195 (Thulium) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away (r)p-process have to overcome coulomb barrier p-process photodisintegration process (γ, n), (γ, α) supernovae temperatures T ∼ 3 · 109K p-only isotopes, eg. 190Pt(Platinum), 168Yb(Ytterbium) rp-process proton captures onto seed nuclei hydrogen rich environment surface of a white dwarf or neutron star Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Neutron Capture Processes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Outline 1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements 2 Supernova Explosions White Dwarfs Classification of Supernovae 3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away White Dwarfs (1) intermediate state of a dying low or medium mass star inner core of former red giant star consists mostly of carbon and oxygen not heavy enough to fuse carbon after fusion stops only electron degeneration pressure supports core against gravitational collaps pdegeneration ∼ pgravitation if Mstar ≤ 1.4 · M ≡ MChandrasekhar if Mstar > MChandrasekhar → supernova Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away White Dwarfs (2) approximately the size of the Earth 0.5 − 0.6M ρ ∼ 9 kg 10 m3 R ∝ 1 white dwarf M1/3 extremely hot (∼ 20, 000K) with small surface →∼ 25 billion years to cool down final state: black dwarf Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Outline 1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements 2 Supernova Explosions White Dwarfs Classification of Supernovae 3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Supernovae stellar explosion which involves the whole star two mechanisms stars with Mstar > 8 · M → after extinction of nuclear fuel → core collapse white dwarfs with Mstar < 8 · M in binary system with red giant → accretion of matter → multiple nova explosions → supernova 20 ± 8 supernovae per millenium in the Milky Way (2/3 visible) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Classification classification in 1939 by Rudolph Minkowski two types with subtypes by chemical experiments in their spectra SN Type I: without hydrogen Balmer line Ia: no hydrogen, strong silicon Ib: weak hydrogen, strong helium Ic: no hydrogen, no helium, weak silicon SN Type II: with hydrogen Balmer line Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Naming of Supernovae prefix “SN” followed by year of discovery first 26 supernovae upper case letter from A to Z following combination of lower case letters aa to zz eg. SN1987A was the first observed supernova in 1987 last supernova in 2005: SN2005nc november 2006: SN2006ot Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Novae close binary system of a white dwarf and a red giant cataclysmic nuclear explosion caused by accretion of hydrogen hydrogen compacts on the surface of the white dwarf under high pressure and temperature fusion (CNO-cycle) heavier fusion products remain on the surface remaining gas is blown away from the surface Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Supernovae Ia (1) same preconditions as for nova heavy elements as fusion products of novae remain on the surface → increasing mass mass slightly under MChandrasekhar → nuclear fusion reaction of carbon and oxygen white dwarf supported against gravity by quantum degeneray pressure no expansion → no cooling unregulated fusion thermonuclear supernova Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Supernovae Ia (2) no remaining compact massive object km companion star escapes with orbital velocity ∼ 100 s → “runaway star” Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Supernovae Ia (3) Supernova Cosmology Project SN Ia always same absolute magnitude → standard candles Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Supernovae II hydrogen Balmer line visible stars ∼ 8 − 30 · M stars heavy enough for fusion up to iron reach always Chandrasekhar limit (∼ 0.9M ) core collapse Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take
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