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Astronomy 535 Stellar Structure Evolution Course Philosophy “Crush them, crush them all!” -Professor John Feldmeier Course Philosophy Contextual stellar evolution – What we see stars doing – The stellar structure that makes stars look that way – The physical processes determining the stellar structure – How stars change with time – The impact of stars upon their environment Motivation for studying stellar evolution • Stars as ensembles – Clusters – Stellar populations – Starbursts My god,it’s full of stars • Stellar yields and environment – Luminosity: Interstellar radiation field, heating, photoionization – Kinetic Energy: Stellar winds, supernovae, feedback – Nucleosynthesis: Chemical evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution Motivation for studying stellar evolution • Stars as ensembles – Clusters – Stellar populations – Starbursts • Stellar yields and environment – Luminosity: Interstellar radiation field, heating, photoionization – Kinetic Energy: Stellar winds, supernovae, feedback – Nucleosynthesis: Chemical evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution Motivation for studying stellar evolution • Stars as ensembles – Clusters – Stellar populations – Starbursts • Stellar yields and environment – Luminosity: Interstellar radiation field, heating, photoionization – Kinetic Energy: Stellar winds, supernovae, feedback – Nucleosynthesis: Chemical evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution Motivation for studying stellar evolution • Stars as ensembles – Clusters – Stellar populations – Starbursts • Stellar yields and environment – Luminosity: Interstellar radiation field, heating, photoionization – Kinetic Energy: Stellar winds, supernovae, feedback – Nucleosynthesis: Chemical evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution Motivation for studying stellar evolution • Stars as ensembles – Clusters – Stellar populations – Starbursts • Stellar yields and environment – Luminosity: Interstellar radiation field, heating, photoionization – Kinetic Energy: Stellar winds, supernovae, feedback – Nucleosynthesis: Chemical evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution Motivation for studying stellar evolution • Stars as ensembles – Clusters – Stellar populations – Starbursts • Stellar yields and environment – Luminosity: Interstellar radiation field, heating, photoionization – Kinetic Energy: Stellar winds, supernovae, feedback – Nucleosynthesis: Chemical evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution Motivation for studying stellar evolution • Stars as ensembles – Clusters – Stellar populations – Starbursts • Stellar yields and environment – Luminosity: Interstellar radiation field, heating, photoionization – Kinetic Energy: Stellar winds, supernovae, feedback – Nucleosynthesis: Chemical evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution Motivation for studying stellar evolution • Stars as ensembles – Clusters – Stellar populations – Starbursts • Stellar yields and environment – Luminosity: Interstellar radiation field, heating, photoionization – Kinetic Energy: Stellar winds, supernovae, feedback – Nucleosynthesis: Chemical evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution Motivation for studying stellar evolution • Evolution of ISM, IGM, gas fraction, composition, star formation, populations, galaxies, baryonic matter in general profoundly depends on stellar evolution • Fits of models to observations by means of free parameters is standard procedure, but gives unreliable or downright bad results for most applications • Must be able to predict evolution of a star as a function of mass and composition to high accuracy • Also necessary to understand individual objects Quantitative Uncertainties in Yields for Massive Stars • Luminosity: – factors of 2 by 25 M – Larger radii, lower Teff, fewer ionizing photons – IMFs derived from observed luminosity functions • Kinetic energy – Order of magnitude uncertainties in mass loss rates – complete uncertainty in composition of winds for a given star • Nucleosynthetic – 2 orders of magnitude in Fe peak abundances from progenitors, reaction calculations, supernova explosion calculations, etc. How to study stars • Too many stellar models are black boxes - tuning a free parameter (i.e. overshooting) to fit one particular observation allows you to predict nothing about other stars How to study stars • Too many stellar models are black boxes - tuning a free parameter (i.e. overshooting) to fit one particular observation allows you to predict nothing about other stars • Stars are not black boxes - including complete physics in a stellar model should give you a correct model How to study stars • Too many stellar models are black boxes - tuning a free parameter (i.e. overshooting) to fit one particular observation allows you to predict nothing about other stars • Stars are not black boxes - including complete physics in a stellar model should give you a correct model • Stars are plasma physics problems - must account for B fields, ionization, multi-component EOS, & charge effects on reactions, radiation transport, hydrostatics, & dynamics How to study stars • 3-pronged approach • Theory based on analytical work and simulations • Terrestrial High Energy Density experiments with lasers and other facilities approximate stellar conditions • Observational tests of theoretical models identify deficiencies in physics, not fits to free parameters How to study stars • 3-pronged approach • Theory based on analytical work and simulations • Terrestrial High Energy Density experiments with lasers and other facilities approximate stellar conditions • Observational tests of theoretical models identify deficiencies in physics, not fits to free parameters How to study stars • 3-pronged approach • Theory based on analytical work and simulations • Terrestrial High Energy Density experiments with lasers and other facilities approximate stellar conditions • Observational tests of theoretical models identify deficiencies in physics, not fits to free parameters Syllabus 1/11 Intro to class Motivation for studying stars Syllabus Timescales 1/13 Equations of hydrodynamics Sound waves Hydrostatic equilibrium Mass-Luminosity relations 1/16 MLK Holiday 1/18 Convection Waves 1/20 Waves Rotation 1/23 **Patrick Leaves for Santa Barbara** EOS Opacities Abundances Syllabus 1/25 Nuclear reactions TYCHO 1/27 The HR diagram CMDs High mass vs. low mass Introduce project 1 (MS as f(z)) 1/30 Pre-MS 2/1 Low mass objects Main sequence starts HW: burning timescales 2/3 pp vs. CNO Convection pp vs. CNO all the problems thereof 2/6 Probably more convection Rotation Syllabus 2/8 Mass-Luminosity relation & lifetimes Cluster ages Composition effects Fun opacity sources 2/10 Misc & catch-up 2/13 **Patrick returns from Santa Barbara** Presentations 2/15 Presentations 2/17 Presentations 2/20 Mass loss Very massive stars Pop III Syllabus 2/22 Post-MS H exhaustion Shell burning RGB 2/24 3alpha degeneracy Tip of RGB He flash 2/27 Red clump/BHB Stellar pulsations Cepheids kappa mechanism Syllabus 3/1 Double shell burning AGB Ratio of BHB/AGB 3/3 C stars, extreme pop II Thermal pulse s-process 3/6 Mass loss PN ejection White dwarfs 3/8 Massive stars Mass loss Wolf Rayets Kinetic luminosity & feedback 3/10 3/13 - 3/17 Spring Break Syllabus 3/20 Presentations 3/22 Presentations 3/24 Presentations 3/27 Misc. & catch-up 3/29 C ignition neutrino cooling C burning 3/31 Ne burning O burning weak interactions Syllabus 4/3 Dynamics of the shell URCA Flame fronts & wierd burning 4/5 detailed balance & thermodynamic consistency QSE NSE Si burning 4/7 Core collapse Nuclear reactions 4/10 Neutrinos Mechanisms 4/12 Asymmetries Mixing Explosive nucleosynthesis 4/14 alpha-rich freezeout r-process uncertainties in nucleo Syllabus 4/17 Core collapse types Spectra Lightcurves 87A 4/19 Type 1a Pair instability GRBs 4/21 GRBs compact objects CVs & XRBs 4/24 **Patrick leaves for Nepal** Population synthesis Stellar pops (Christy?) Syllabus 4/26 Misc. & catch-up 4/28 Presentations 5/1 Presentations 5/3 Presentations Timescales Gravitational timescale 1/ 2 R 1/ 2 R 3 ff g GM Hydrodynamic timescale hyd c s ; c s2 P S R Note that in hydrostatic equilibrium 1 dP GM 2 dr r P GM R HSE hyd ff Hydrostatic adjustment timescale at 1M White Dwarf: few s Main sequence: 27 min (sun) Red Giant: 18 days For most phases HSE << evol Timescales Kelvin-Helmholtz (Thermal) KH E grav L Gm 2 GM 2 E grav r 2R M Gm E grav dm 0 r GM 2 KH 2RL M R ; m ,r 2 2 For sun KH ~ 10 Myr Timescales Nuclear or Evolutionary Timescale E nuc nuc L Quick ‘n’ dirty solar lifetime estimate QHHe=6.3x1018erg g-1 (0.7% of rest mass energy) assume 10% of H gets burned Enuc = 2x1033g x 0.1 x 0.007 x c2 = 1.26x1051 erg L = 4x1033 erg 3x1017 s = 10 Gyr