Astronomy 535 Stellar Structure Evolution. Course Philosophy “Crush them, crush them all!”...
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Transcript of Astronomy 535 Stellar Structure Evolution. Course Philosophy “Crush them, crush them all!”...
Astronomy 535Stellar 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
• 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
My god,it’s full of stars
• 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
Motivation for studying stellar evolution
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
Syllabus1/11
Intro to classMotivation for studying starsSyllabusTimescales
1/13Equations of hydrodynamicsSound wavesHydrostatic equilibriumMass-Luminosity relations
1/16MLK Holiday
1/18ConvectionWaves
1/20WavesRotation
1/23 **Patrick Leaves for Santa Barbara**EOSOpacitiesAbundances
Syllabus1/25
Nuclear reactionsTYCHO
1/27 The HR diagramCMDsHigh mass vs. low massIntroduce project 1 (MS as f(z))
1/30Pre-MS
2/1Low mass objectsMain sequence startsHW: burning timescales
2/3pp vs. CNOConvection pp vs. CNO all the problems thereof
2/6Probably more convectionRotation
Syllabus2/8
Mass-Luminosity relation & lifetimesCluster agesComposition effectsFun opacity sources
2/10Misc & catch-up
2/13 **Patrick returns from Santa Barbara**Presentations
2/15Presentations
2/17Presentations
2/20Mass lossVery massive starsPop III
Syllabus2/22
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
Syllabus3/1
Double shell burningAGBRatio of BHB/AGB
3/3C stars, extreme pop IIThermal pulses-process
3/6Mass lossPN ejectionWhite dwarfs
3/8Massive starsMass lossWolf RayetsKinetic luminosity & feedback
3/10
3/13 - 3/17Spring Break
Syllabus3/20
Presentations3/22
Presentations3/24
Presentations3/27
Misc. & catch-up3/29
C ignitionneutrino coolingC burning
3/31Ne burningO burningweak interactions
Syllabus4/3
Dynamics of the shellURCAFlame fronts & wierd burning
4/5detailed balance & thermodynamic consistencyQSENSESi burning
4/7Core collapseNuclear reactions
4/10NeutrinosMechanisms
4/12AsymmetriesMixingExplosive nucleosynthesis
4/14alpha-rich freezeoutr-processuncertainties in nucleo
Syllabus4/17
Core collapse typesSpectraLightcurves87A
4/19Type 1aPair instabilityGRBs
4/21GRBscompact objectsCVs & XRBs
4/24 **Patrick leaves for Nepal**Population synthesisStellar pops (Christy?)
Syllabus
4/26
Misc. & catch-up
4/28
Presentations
5/1
Presentations
5/3
Presentations
TimescalesGravitational timescale
Hydrodynamic timescale
Note that in hydrostatic equilibrium
Hydrostatic adjustment timescale at 1M
White Dwarf: few s
Main sequence: 27 min (sun)
Red Giant: 18 days
For most phases HSE << evol
€
ff =R
g
⎛
⎝ ⎜
⎞
⎠ ⎟
1/ 2
=R3
GM
⎛
⎝ ⎜
⎞
⎠ ⎟
1/ 2
€
hyd =cs
R; cs
2 =∂P
∂ρS
€
−1
ρ
dP
dr= −
GM
r2
⇒P
ρ≈
GM
R
⇒ τ HSE ≈ τ hyd ≈ τ ff
Timescales
Kelvin-Helmholtz (Thermal)
For sun KH ~ 10 Myr
€
KH =Egrav
L
Egrav ≈Gm 2
r ≈
GM 2
2R; m =
M
2,r =
R
2
Egrav =Gm
rdm
0
M
∫
τ KH ≈GM 2
2RL
Timescales
Nuclear or Evolutionary Timescale
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
€
nuc =Enuc
L