Physics of Stars I
恒星物理学特論 I
Masaomi Tanaka
田中 雅臣

Masaomi Tanaka (田中 雅臣)
hMps://www.astr.tohoku.ac.jp/~masaomi.tanaka/

Research topics- Time-domain astronomy- Transients (e.g., supernovae,neutron star mergers)

Observa<ons- Wide ﬁeld survey (Subaru, Kiso)- Spectroscopy and spectro-polarimetry

Theory- RadiaYve transfer simulaYons

Born in Nagoya (Aichi)
Grew up in Chita peninsula
2001-2009: U. Tokyo
2009: PhD at Univ. of Tokyo
2009-2011: Kavli IPMU
2011-2018: NAOJ
2018-now: Tohoku Univ.

Research interests

Supernova- Supernovae- Neutron star merger(gravita<onal wave source)- Anything variable on the sky

Why do we study transients?
- Extreme physical condi<on- End point of stellar evolu<on- Origin of the elements- Many unsolved mystery“<me-domain astronomy”

Neutron star merger

Elements around us
Air
Argon (Ar) 1.3 %CO2 0.05 %Neon (Ne) 0.001 %Oxygen (O)23%
Nitrogen (N)76%* Mass ra<o (dry air)Our body
Ca 1.5%

P 1%

N 3%

Hydrogen (H)10%

Carbon (C)18%

Oxygen (O)65%

S 0.25%
K 0.20%Na 0.15%
Cl 0.15 %Mg 0.05 %The earth (crust)
Na 2%
Ca 3%

K 2%
Mg 1.5%

Fe 4%

Aluminum (Al)8%

Silicon (Si)30%

Oxygen (O)48%* Mass ra<oThe beginningof the Universe
H, He, Li

C: Rhys Taylor, Cardiff University(Planck mission)Now
137 億年(13.7 billion yr )Our Universe“Heavy elements”
2%

O 0.6%
C 0.2%
Ne 0.1%
Fe 0.1 %Helium (He)25%

Hydrogen (H)73%*Mass ra<oElement abundances in the Universe

12Mass fraction (H=10 )

H1012

He10C

1010810610410210010-2OFe

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Atomic number Z*Mass ra<o

Goals of this lecture• Standard proper<es of stars• Stellar structure and proper<es• Stellar evolu<on• Origin of the elements in the Universe• Nucleosynthesis in stars and supernovae• Explosion mechanism of supernovae• Topics in <me-domain astronomy• Radia<on from explosive phenomena• Mul<-messenger astronomy
Minimum required knowledge for galac<c astronomy

Course material and schedule
haps://www.astr.tohoku.ac.jp/~masaomi.tanaka/tohoku2020

Contents • Overview* ~70% blackboard~30% slides• Stellar structure and proper<es• Stellar evolu<on• Thermonuclear supernovae• Core-collapse supernovae• Radia<on from supernovae• Time-domain astronomy• Neutron star merger and mul<-messenger astronomy• Origin of the elements and chemical evolu<on of the Universe

Credit
成績• Assignments / レポート課題

A few rules about this lecture• Please try order es<ma<on by yourself• This is essenYal for astrophysics• Please ask ques<ons• Your quesYons certainly help others’ understanding(you can ask quesYons in Japanese)• You can use “chat” window• Please relax and enjoy• You can bring coﬀee/tea or chocolates/cookies, …

Sec<on 1.
Overview: Life of stars, supernovae,
and origin of the elements
1.1 Stellar lives and supernovae
1.2 Origin of the elements

1181 1054 1006

Guest stars
客星古現例

明月記
藤原定家(1162-1241)

フェリス女学院大学蔵『新三十六歌仙画帖』

冷泉家時雨亭叢書

A guest star appeared
and it shined as Mars on May 1st in 1006.

Crab Nebula = M1NASA/HST

1572
Tycho Brahe“Stella Nova”1604Johannes Kepler“Astronomie+Populaire”++
by+Camille+Flammarion+(Paris,+1884)

Historical supernovaeName
SN 185SN 1006
CrabSN 1181
TychoKepler
SN 1987A

Loca<onGalac<cGalac<cGalac<cGalac<cGalac<cGalac<c
LMC

Year
185
1006
1054
1181
1572
1604
1987

Magnitude
-8?
-9?
-4?
0-4
-3
3~ 1 supernova every 100-200 yearsB. J. Fulton

SDSSHistory of SN discovery

hMp://probimobrien.com/2014/02/supernova-2014j-in-m82/

Light curve of supernovae(brightness as a func<on of <me)-20Type Ia
Type Ib and Ic
Type II1043 erg s-11042

1041

Absolute magnitude-18-16-14-12-10050

100150200
250
Days after the explosion

300350

Stellar life

(C: Essay Web)

Hertzsprung-Russel diagram
Luminosity
Red giants

Mainsequence

White dwarfs

Temperature (K)hap://astronomy.nmsu.edu/geas/lectures/lecture23/slide04.html

Mass - luminosity rela<on of the main sequence stars
6Star with M = 10 Msun=>1.0L ~ 104 Lsun=> Life<me~ 1/103 of the Sun
0.5~ 1010 yr (100億年)/103

L ~ M4log (R / Rsun)log (L / Lsun)

4

20~ 107 yr (1000万年)

0.0−0.5

More massive stars
have shorter life<me−2−10log (M / Msun)

1−1.0−10log (M / Msun)

Lectureby Pols of doubleFigure 1.3. Mass-luminosity (left) and mass-radius (right) relations
forNotecomponents

Applica<ons to galaxy studies
Spiral galaxy

Ellip<cal galaxy

M101

ESO 325-G004(C) NASA, ESA- Star forming- More “young" stars- More massive stars- Blue (high T radia<on)- No star forma<on- Old stars- Less massive stars- Red (low T radia<on)1. Massive stars
軽い星赤色巨星

惑星状星雲
M > 10 Msun

~ 10 Myr

図の大きさは天体の大きさと一致していません(C: Essay Web)

白色矮星

HHeFe

SiC+O

Ne + Mg

Images are not to scaleCollapse(< 1 sec)

Neutron star
orBlack holeSupernova!

1-10 Gyr
赤色超巨星

超新星爆発

重い星
2. Low-mass stars

中性子星
M < 10 Msun

(C: Essay Web)

ブラックホール

図の大きさは天体の大きさと一致していません

H

Images are not to scale

HeC+O

White dwarf

C+OBinary system

White dwarf

David A. Hardy

Thermonuclear explosion

CSiOFeSupernova!

Progenitor
Elements

Core-collapse SNe

Thermonuclear SNe

Massive starsShort lifeYme

Low-mass stars (in binary)Long lifeYmeO, Mg, Ca, …
(progenitor star)

Si, Ca, Fe, …
(explosion)

The elements around us are made by stars and SNeThe origin of elements
Big bang
Stars and supernovae

NhMcTs Og

Let’s feel SN explosion
Tycho’s supernova
Q. What is the average
Velocity of SN?

R ~ 1019 cm（10 light year ~3 pc）
Observed by Tycho Brahe in 1572
(Type Ia)

Velocity = Distance/<meDistance: 1019 cm
Time: ~400 years
Velocity = 1019 / (400 x 3 x 107)
~ 109 cm/s ~ 10,000 km/s10 light year = 10 year with light speed
SN takes 400 year to expand
Velocity = c/40= (300,000 km/s) / 40

~10,000 km/s！

10,000 km

12E = Mv
2Q. How large is the kine<c energy?

Msun = 2 x 1033 g

Ekin ＝ 1/2 x Mass x (Velocity)2＝1/2 x (2 x 1033 g) x (109 cm/s)2~ 1051 erg

Sec<on 1.
Overview: Life of stars, supernovae,
and origin of the elements
1.1 Stellar lives and supernovae
1.2 Origin of the elements

Cosmic abundances (atomic number)

12Mass fraction (H=10 )H1012He10C1010810610410210010-2O

Fe0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Atomic number Z*Mass ra<oCosmic abundance (mass number)
100-1H He-2

O

1010C-3

10Fe

Mass frac<on

質量割合-410-510sプロセス

10-7Sr-610rプロセス
sプロセス

Ba-810-9rプロセス
sプロセス

Au PbPt

1010-10

10-11

050

100
150200
質量数 Mass number250

Our understanding about thenucleosynthesis is correct??

Chemical evolu<on of the UniverseFeCore-collapse SNeMg

Thermonuclear SNeTime109 yr 1010 yr
Core-collapse SNeTimeStars formed recently should have low Mg/Fe ra<osOur Galaxy

Stars keep informa<onabout nucleosynthesis in the past
“Galac<c archeology”

hMp://astronomy.swin.edu.au/cms/astro/cosmos/T/Thick+Disk

[ Mg/Fnature and extent of n-capture nucleosynthesis in the early Galaxy. Abundance signatures of these0.5
elements can help to identify the parameters of the first stars—long since gone—and the sites forr- and s-process nucleosynthesis (Cowan & Sneden 2006). There are many ways to approach this0issue. We
begin in Figure 14 by contrasting the abundance behavior as a function of metallicityof the α element Mg and the n-capture element Eu. Only large stellar samples are employed forthese –0.5
correlations; the literature sources are listed in the figure caption.

Abundance ra<o in Galac<c stars (Mg/Fe)[ Mg/Fe][Eu/Fe]1.5
1.5

abHaloDisk

1.0
1.0
0.5
0.500
–0.5
–0.5

1.5

b–3

–2–10

[Fe/H][Eu/Fe]Figure 14
Sneden+08
1.0[Mg/Fe] and [Eu/Fe] abundances as a function of [Fe/H] metallicity for halo and disk stars. For this figure
the data have been taken only from large-sample surveys: Fulbright (2000); Reddy et al. (2003); Cayrel et al.
(2004);0.5Cohen et al. (2004); Simmerer et al. (2004); Barklem et al. (2005, red points); Reddy, Lambert &Allende Prieto (2006); François et al. (2007). In both panels the dotted lines represent the Solar abundance
ratios. In panel b, the solid red line is a least-square fit to the Eu data, and the two dashed black lines indicate
0the approximate extent of the Eu/Fe data (similar to Cowan & Thielemann 2004).

TimeLonger delay <me for Type Ia SNeSummary• Stars synthesize heavy elements• Stars evolve with <me• Core-collapse supernovae• Origin of the elements such as Oxygen and Magnesium• Thermonuclear supernovae• Origin of Fe-peak elements• Supernova explosions• V ~ 10,000 km/s
• Ekin ~10 erg (10 J) => Feedback to galaxy formaYon• Stellar nucleosynthesis is imprinted in Galac<c stars5144

Let’s understand these ques<ons
Knowing = Understandingwith the word of physics• Why do some stars explode?
• Why don’t normal star explode?
• Why do stars show L ~ M ?
• Why do stars evolve?
• Why does the des<ny of stars depend on the mass?
• Why does stellar core collapses?
• Why is the energy of supernova so huge?
•…
4

3 steps of learning

Short-term memory

1. Know
Have informa<on<= Google is much beaer
than we are!!

- L ~ M4
Long-term memory
2. Connect with other knowledge
Integrate knowledge, put it in some contexts- Massive stars have shorter lifeYme- Physics behind it (radiaYon energy/diﬀusion Yme)

3. Use the knowledge
Apply to other cases- Use galaxy color as indicator of star formaYon- radiaYon energy/diﬀusion Yme => L vs M of other systems=> understand“make it sYck - The Science of Successful Learning” Brown et al. 2016

Thermodynamics

Electromagne<smClassical
mechanics

Sta<s<calmechanics

Astrophysics
Hydrodynamics

Rela<vityQuantum
mechanics
Nuclear physics