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 Away Core Collapse (1) Collapse Accelerated by Two Processes
photodisintegration photodissociation of iron nuclei by high energy γ-rays γ +56 Fe → 134He + 4n γ +4 He → 2p+ + 2n high binding energy of iron → requires energy radiation pressure decreases inverse β-decay − e + p → n + νe loss of free electrons decreasing pressure Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Core Collapse (2)
core collapse takes only some milliseconds in a distance of 20-50 km of the center pressure not high enough for matter to respond
vmatter > vsound shock wave because of photodissociation mostly neutrons in the inner core → degeneration pressure → core almost instantanously incompressible shockwave reflected Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Core Collapse (3) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Core Collapse (4)
high temperature gas & neutrons from the center → r-process Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Core Collapse (5) Cooling of the Inner Core
electron/positron pair production 2γ → e+ + e− high cross section → cannot escape re-annihilation neutrino/antineutrino pair production 2γ → ν +ν ¯ can finally escape → cooling liberated gravitational binding energy 99% in neutrinos 1% kinetic energy of explosion 0.01% photons 53 19 neutrino luminosity L ∼ 3 · 10 erg/3sec ∼ 3 · 10 L Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Core Collapse (5) Observation of Supernovae
observation of neutrinos before optical detection scattering of ν and γ cross section σγ σν SN1987A: Kamiokande II SuperNova Early Warning System (SNEWS) Super-Kamiokande LVD SNO AMANDA Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Subtypes of Supernovae II
supernovae II-P high ejected mass and velocity of shell decreasing luminosity compensated by fast expanding shell light curve shows plateau domain maximum luminosity strongly connected to radius of progenitor star → peak value of luminosity widely spread supernovae II-L low expansion velocity linear decreasing luminosity marginally spread peak luminosity Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Supernovae Ib/Ic
stars with mass > 30 · M Wolf Rayet phase core collapse as in SN II supernova Ib/Ic 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
Neutron Stars (1)
neutron stars proposed by Walter Baade and Fritz Zwickly in 1933
mass of 1.35 − 2.1M 6 radius ∼ 10 − 20km (R ∼ 10 km) high rotation speed (∼ 1/700 − 30sec) because angular momentum conserved escape velocity ∼ 150, 000km/s supported by neutron degeneration pressure slowing down between 10−10 − 10−21sec/rotation Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Neutron Stars (2) Different Types Of Neutron Stars
x-ray bursters neutron star in binary system accreting matter from companion star, causing irregular X-ray bursts pulsars neutron star emitting pulses of radiation magnetars neutron star with extremly strong magnetic fields magnetic fields of ∼ 100GT rotation period ∼ 5 − 12sec Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Pulsars (1)
first pulsar discovered by Jocelyn Bell Burnell and Antony Hewish in 1967, PSR1919+21 “LGM-1” very regular periodical signal detectable radio array → pulses of radiation solution: rotating neutron stars sources of energy rotation powered pulsars accretion powered pulsars → X-rays magnetic powered pulsars Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Pulsars (2) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Pulsars (3) Millisecond Pulsars
in 1982 discovery of millisecond pulsars “MSPs” rotation periode ∼ 1.6ms extraordinarily stable rotation → astronomical clocks measurement of gravitational waves Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Crab Nebula (1)
observed by John Bevis in 1731, Earl of Rosse in the 1840s SN1054 pulsar in its centre (∼ 30rounds/sec) radiation from gamma rays to radio waves
progenitor star 8 − 12M Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Crab Nebula (2)
filaments remnants of the progenitor star’s atmosphere ionised helium and hydrogen, carbon, oxygen, nitrogen, iron, neon, sulphur density ∼ 1, 300particles/cm3 diffuse blue region → synchroton radiation pulsar → strong magnetic field radiation used for studying objects that occult it Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Crab Nebula (3) Studying Objects that Occult the Crab Nebula Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Crab Nebula (4) Path of Titan in 2003 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
Black Holes (1)
body so massive that light can’t escape concept by English geologist John Michell in 1784
collapse of neutron star > 3 · M → Tolman-Oppenheimer-Volkoff limit = 2GM Schwarzschild Radius RSchwarzschild c2 event horizon theory of general relativity curvature → ∞ singularity at the center Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Black Holes (2) Light Cone Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
Black Holes (3) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Black Holes (4) Supermassive Black Holes
supermassive black holes in center of most galaxies → collapse of dense cluster of stars large amouts of mass accreting onto stellar “seed” black hole fusion of smaller black holes 9 masses up to 10 · M jets acceleration of high energetic cosmic rays Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away
For Take Away
Diffrent types of supernovae: core collapse vs. thermonuclear supernovae Supernovae Ia used as cosmic standard candles. Final stages of stellar evolution are black dwarfs, neutron stars and black holes, depending on the mass of the star. Heavy elements produced in the s-process in red giant stars and in the r-process in supernova explosions.