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STELLAR EVOLUTION – THE STANDARD SOLAR MODEL AND SOLAR NEUTRINOS – MARIE ZECH Content: 1. Our sun – basic facts 2. SSM – the Standard Solar Model 1. 2. 3. What is the SSM? Helioseismology The solar abundance problem 3. Solar Neutrinos 1. 2. 3. 4. What is a neutrino/ solar neutrino? Detection of neutrinos Solar neutrino problem Neutrino oscillation 4. Summary 5. Sources Marie Zech 2 1. Our Sun - Basic Facts G –type main sequence star yellow dwarf diameter: 109 x Earth mass: 330,000 x Earth Population I: heavy element rich star temperature in the core: up to 15.7 million K on the surface: ≈ 5,800K Marie Zech composition of our sun: Hydrogen Helium Oxygen Carbon Iron Neon Nitrogen Silicon Magnesium Sulfur 73.46% 24.85% 0.77% 0.29% 0.16% 0.12% 0.09% 0.07% 0.05% 0.04% 3 1. Our Sun – Basic Facts formed ~4.567 billion years ago formation may have been triggered by nearby supernovae NOW: roughly middle aged will remain fairly stable FUTURE: red giant becomes very large http://www.nasa.gov/images/content/171926main _heliolayers_label_lg.jpg Marie Zech 4 2. The Standard Solar Model 2.1 What is the SSM? mathematical treatment of the sun as a spherical ball of gas principal approximations: hydrostatic equilibrium energy transport by photons or convective motion energy generation by nuclear reaction: 4𝑝 → 4𝐻𝑒 + 2𝑒 + + 2ν𝑒 + 26.73𝑀𝑒𝑉 abundance changes caused solely by nuclear reactions Marie Zech 5 2. The Standard Solar Model major input parameters/ functions: relative chemical abundances: hydrogen(X), helium(Y), heavy elements(Z) 𝑋 + 𝑌 + 𝑍 = 1.0 radiative opacity equation of state luminosity age nuclear parameters used to test validity of stellar evolution theory Marie Zech 6 2. The Standard Solar Model figure d: dependence of electron number density upon solar radius Marie Zech 7 2. The Standard Solar Model Properties of the solar model as a function of time Marie Zech 8 2. The Standard Solar Model 2.2 Helioseismology: study of solar seismology provides information about the interior of the body the surface of the sun is filled with patches that oscillate the sun oscillates in three dimensions rich spectrum of frequencies these frequencies provide information about temperature and density distribution within the sun and it´s chemical composition Marie Zech https://www.spaceinn.eu/project /science/helioseismology/ 9 2. The Standard Solar Model 2.3 The solar abundance problem inconsistency between the SSM and the helioseismic data connection to neutrinos: Temperature dependent 8𝐵 and 7𝐵𝑒 neutrino fluxes are sensitive to metallicty → cross – check conclusions from helioseismology measurements of CN solar neutrino flux potential to directly measure solar core abundance of C+N Marie Zech 10 2. The Standard Solar Model GS98 – high metallicity AGSS09 – low metallicity Marie Zech 11 2. The Standard Solar Model SSM characteristics compared to helioseismic values 𝑅𝐶𝑍 is the radius to the convective zone δ𝑐/𝑐 is the average fractional discrepancy in the sound speed, relative to helioseismic values Marie Zech 12 3. Solar Neutrinos 3.1 What is a neutrino? lepton, charged neutral 3 flavours: electron neutrinos muon neutrinos tau neutrinos solar neutrinos are created in the core by nuclear reactions neutrino fluxes are sensitive to the core temperature Marie Zech 13 3. Solar Neutrinos Marie Zech 14 3. Solar Neutrinos estimated neutrino fluxes of different SSMs Marie Zech 15 3. Solar Neutrinos 3.2 Detection of neutrinos cannot be detected directly detector are often build underground for protection from cosmic rays and background radiation 90ies: Super Kamiokande in Japan 50,000 t Water – Cherenkov – detector can´t distinguish between different neutrino flavours 1999 – 2006 Sudbury Neutrino Observatory in Canada heavy water possible to differ between muon and tau / electron neutrinos via statistics Marie Zech 16 3. Solar Neutrinos Super Kamiokande Fish-eye photo of the SNO Detector http://www-sk.icrr.u-tokyo.ac.jp/sk/gallery/wme/sk_01hwm.jpg https://www.snolab.ca/sites/default/file s/images/SNO-hi%20res.preview.jpg Marie Zech 17 3. Solar Neutrinos 3.3 Solar neutrino problem pattern of fluxes in contrast to SSM predictions significant deficit of electron neutrinos and muon neutrinos day/ night differences (upward going Neutrinos in detector) http://www-sk.icrr.u-tokyo.ac.jp/sk/sk/neutrino-e.html Marie Zech 18 3. Solar Neutrinos superposition of neutrino eigenstates 3.4 Neutrino Oscillation quantum mechanical interference phenomenom flavour of neutrino can change while „flying“ probability of this change can be calculated solution to solar neutrino problem: missing neutrinos changed e.g. into not with Kamiokande or SNO detectable tau neutrinos NEW: neutrinos are not without a mass new physics aside from standard model of astrophysics needed Marie Zech http://www-sk.icrr.utokyo.ac.jp/sk/sk/neutrino-e.html 19 3. Solar Neutrinos Winners of the Nobel Prize 2015 in Physics Takaaki Kajita Arthur B. McDonald https://www.snolab.ca/news/2015-10-15-canadianscientist-shares-nobel-prize-win-physics-snoexperiment http://www.nobelprize.org/nobel_pr izes/physics/laureates/2015/images/ kajita-photogallery.jpg Marie Zech 20 4. Summary data from low Z abundance SSM showd in comparison to helioseismic data inconsistencies to check data: neutrino fluxes not as much neutrinos were detected as calculated → solved by neutrino oscillation (change of neutrino flavour is possible) → new kind of physics is needed, standard model of astrophysics is not entirely correct Marie Zech 21 5. Sources: Annu. Rev. Astron. Astrophys. 2013.51:21-61 Bahcall, John N: Neutrino Astrophysics, Cambridge University Press, 1989 Physik Journal 14 (12), WILEY-VCH Verlag GmbH&Co.KGaA, Dezember 2015 https://www.snolab.ca/ http://www-sk.icrr.u-tokyo.ac.jp https://en.wikipedia.org/wiki/Sun https://en.wikipedia.org/wiki/Solar_neutrino https://en.wikipedia.org/wiki/Neutrino Marie Zech 22