Sec on 6.
Stellar evolu on (III)
6.1 Equa ons for stellar evolu ontitititititi

6.2 Calcula ons of stellar evolu on

Let’s understand these ques ons
with the words of physics• Why are stars so luminous?
• Why do stars show L ~ M ?
• Why do stars evolve?
• Why does the des ny of stars depend on the mass?
• Why do some stars explode?
• Why don’t normal star explode?
• Why does stellar core collapses?
• Why is the energy of supernova so huge?
•…
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Sec on 6.
Stellar evolu on (III)
6.1 Equa ons for stellar evolu ontitititititi

6.2 Calcula ons of stellar evolu on(A color version of this figure is available in the online journal.)(A color version of this figure is available in the online journal.)

Figureblack23. line)
2 M!and, Z MESA= 0.01
tracksupgrayto thefirsi(solidstar(thickline)(solid black line) and MESA star (thick gray line

Low/intermediate
mass stars

tiFigure 22. Top: MESA star H-R diagram for 2–10 M! models from the PMSto the end of the first thermal pulse (2–7 M! ) or into C-burning (8 and 10 M! ).

mass, and hence luminosity, in the EVO
mass, andhenceenvelope
luminosity,the EV
maintainsimilarmassinevolution
maintainsimilarmass evolutio
theparameter
ηBlenvelopein the mass-loss
formu
the parameter
mass-loss
MESA
star andηBl
0.1ininthe
EVOL.
Everyform
eff
MESA thestar
andstar
0.1 inmodel
EVOL.
etailorMESA
to Everythe EVOtailor
the evolution
MESA starmodelto the toEV
theAGBis very
sensitive
the AGBevolutionvery sensitive
towhichdepends
on theismixing
assumption
which depends onthe mixing
assumptio
implementation
duringthe precedingHe
implementation
duringthe preceding
H
Consequently,
small
differenceson the TPConsequently,
small
differences
the TP
when
comparing
tracksfrom twoon
codes.
Coreonwhen
comparing
tracks23,
fromcodes.
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As shown
Figure23,
the EVOL
well ininofthetheH-R
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Tabla=>compare
Expansionenvelope
properties
differinbythelessthan5%. MESA
compare well
H-R
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Red
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imposeadifferminimumsizethanon convectio
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overshootis ignored.
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the coreovershootmixingis ignored.
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EVOL sequence
thecorfi
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processes
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MESA
star calculations,as revealedare
in pFnucleosynthesis.
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ofMESAstarstar
to calculateastherevealed
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MESA
calculations,ininsmoothandtocontinuous
evenof aMESA
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calculate manner
the evolutio
thermalpulseandphasesand beyond
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mannereve
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evolution
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thepanelshows
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top panelshows
the theevolution
in theC/O
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panel
shows coolingthe evolution
duringthe Heflash(duethe pressuredPaxton
etal.to2011C/O core.
The
adiabaticcoolingin theof the C/O core) is evident in the downTheAstrophysicalAstrophysical Journal
Journal Supplement(35pp),
2011
January
The
SupplementSeries,Series,192:3
192:3(35pp),
2011
January

Massive stars(un l He-burning)

Core contrac on=> Expansion of the envelope=> Red super giant

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Figure 29. Top: H-R diagram for 10–100 M! models from the PMS to the end ofcore Helium burning for Z = 0.02 but with zero mass loss. Bottom: trajectories

Figure 30. Evolution of the central temperature andmetallicity Mi = 25 M! models from different stella
Figure30. Evolutionof thecentral
temperatur
locationsof corehelium, carbon,neon,oxygen,and sili
1/3
as ismetallicity
the relationM
Tci ∝=ρc25 .M! models from differen
locations of core helium, carbon, neon, oxygen, a(A color version of this figure1/3
is available in the online

ρc al.
. 2011
as is the relation
Tc ∝ etPaxton(A color version of this figure is available in theContrac on of the core
= Expansion of the envelope

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Evolu on in the rho-T plane is determinedby the proper es of the coreT ~ M2/3 ρ1/3
M decreases => Lower part of the ρ-T plane

Massive stars（un l Si burning）

Finally degeneracy pressure
becomes importantdege
nerateelectrons

relativistic electronsti

textbook by Pols

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How can we calculate stellar evolu on?

Sec on 6.
Stellar evolu on (III)
6.1 Equa ons for stellar evolu ontiti

ti

ti

titi

6.2 Calcula ons of stellar evolu ontt

MESA codeh p://mesa.sourceforge.net/index.html

1 Msun (ρ-T)

1 Msun (HR diagram)20 Msun (ρ-T)

20 Msun (HR diagram)tiElemental distribu on before core-collapse SN

Mass fraction log10(x)nu. Rev. Astron. Astrophys. 2013.51:457-509. Downloaded from www.annualrev
ed by Kokuritsu-Tenmondai Libr. - National Observatory of Japan on 09/08/16. F

0–6

Figure 1
1256Ni

54Fe

23416O3454He561H24Mg

228Si

–4

6–6

d2

–6

Central remnant

c1

Mass fraction log10(x)–6
1Mr (M )

05–4

40Ca

1Mr (M )Nomoto+13

“Kippenhahn diagram”

titt(C) A. Hegerh ps://2sn.org/stellarevolu on/explain.gif

Summary: stellar evolu on (III)tititititifitititititititititi• Equa ons for stellar evolu on• Equa on of mo on• Equa on of state• Energy equa on• Nuclear reac ons• Stellar evolu on calcula ons• Series of hydrosta c con gura ons for a given ini al mass
• Rota on, metallicity and so on

Thermodynamics

Electromagne sm

Classical
mechanics

Sta s calmechanics

Astrophysics
Hydrodynamics

titititiRela vity

Quantummechanics
Nuclear physics