Transcript Astronomy 535 Stellar Structure Evolution

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
For sun KH ~ 10 Myr
M
R
,r 
2
2
Timescales
Nuclear or Evolutionary Timescale
 nuc 
E nuc
L
Quick ‘n’ dirty solar lifetime estimate
QHHe=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