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2.9.13
Star and Planet Formation
Master course 2013
Carsten Dominik
8 weeks (2.9. - . – 25.10.2013)
2 lectures per week (Monday 13:00 & Thursday 9:00, G2.04)
2 problem session/project meetings per week
(Monday 15:100 G5.29, Friday 15:00 A1.08)
Exam on Thirsday, 24.10, 13-16, room B0.207
Star and Planet Formation
Course outline:
1. 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 
10. 
11. 
12. 
13. 
14. 
Introduction: The Solar System Context
Molecular clouds
Cloud equilibrium and Stability
Collapse of clouds
Protostars & pre-main-sequence evolution
High-mass Star Formation
Viscous Accretion Disks
Irradiated Disks
Observations of Disks
From dust to planetesimals
From planetesimals to planets
Giant Planet Formation
Planet-Disk interaction, Migration
Population Synthesis
Star and Planet Formation
Exercise hours:
Problems should have been worked out before, solutions will
be discussed. The projects will be discussed there as
well.
Projects:
Small programming project. Details in todays problem
session.
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2.9.13
Star and Planet Formation
Books:
S.W.Stahler & F.Palla “The Formation of Stars”,
Wiley-VCH, ~85 €
P.Armitage “Astrophysics of Planet Formation”,
Cambridge University Press, ~48 €
Syllabus (written in collaboration with Inga Kamp):
Online. First half is finished, second half comes later
All material will be on Blackboard.
People who provided material:
The Solar System Context
1. 
A historical perspective
I. 
II. 
2. 
3. 
The Sun as a star
Models of Solar System Formation
Observational Constraints
I. 
Regularity
II.  Composition
III.  Asteroid Belt
IV.  Ages from radioactive dating
V. 
Deuterium
VI.  Dynamics of Small Bodies
VII.  Angular Momentum
VIII. Minimum Mass Solar Nebula
How did the Sun form?
I. 
II. 
III. 
IV. 
4. 
Molecular Clouds
Starless Cores
Young Stellar Objects
Jets & Outflows
How did the planets form?
I. 
Protoplanetary Disks
II.  Debris Disks
III.  Exoplanets
1. A historical perspective
Our Solar System
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1. A historical perspective
The geocentric model
Before the 16th century:
geocentric model (Earth at
the center)
only Aristarchos of Samos
(280 BC) had suggested a
heliocentric model
Cosmographia (1539)
1. A historical perspective
The geocentric model
Aristotele’s school:
1.  If the Earth rotates around the Sun, birds should actually stay
behind because of the movement of the Earth on its orbit.
2.  If the Earth rotates around its axis (as required to explain day
and night), things should fly off the spinning planet.
3.  If the Earth rotates around the Sun, we should observe
parallaxes for the fixed stars. "
1. A historical perspective
The geocentric model
Aristotele’s school:
1.  If the Earth rotates around the Sun, birds should actually stay
behind because of the movement of the Earth on its orbit.
2.  If the Earth rotates around its axis (as required to explain day
and night), things should fly off the spinning planet.
3.  If the Earth rotates around the Sun, we should observe
parallaxes for the fixed stars. "
In which of these statements was he right ?
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1. A historical perspective
The geocentric model
Aristotele’s school:
1.  If the Earth rotates around the Sun, birds should actually stay
behind because of the movement of the Earth on its orbit.
Inadequate understanding of physics !
2.  If the Earth rotates around its axis (as required to explain day
and night), things should fly off the spinning planet.
Inadequate understanding of physics !
3.  If the Earth rotates around the Sun, we should observe
parallaxes for the fixed stars. "
1. A historical perspective
The geocentric model
Aristotele’s school:
1.  If the Earth rotates around the Sun, birds should actually stay
behind because of the movement of the Earth on its orbit.
Inadequate understanding of physics !
2.  If the Earth rotates around its axis (as required to explain day
and night), things should fly off the spinning planet.
Inadequate understanding of physics !
3.  If the Earth rotates around the Sun, we should observe
parallaxes for the fixed stars. "
True, but parallax too small to be observed at that time.
Largest parallax: 0.77” for Proxima Centauri (1.3 pc)
1. A historical perspective
The heliocentric model
Nicolaus Copernicus (1473 - 1543)
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1. A historical perspective
The heliocentric model
Johannes Kepler (1571 - 1630)
1. A historical perspective
Kepler’s laws
1.  The planets revolve on elliptical orbits around the Sun, with the
Sun in one focus.
periastron"
apastron"
periastron
"
2.  The area swept out by the radius
vector
from
the Sun to the
apastron"
distance"
distance"
planet per unit time is constant
3.  The square of the orbital period T divided by the cube of the
mean distance from the Sun a is the same for all planets
1. A historical perspective
Kepler’s laws
1.  The planets revolve on elliptical orbits around the Sun, with the
Sun in one focus.
2.  The area swept out by the radius vector from the Sun to the
planet per unit time is constant
3.  The square of the orbital period T divided by the cube of the
mean distance from the Sun a is the same for all planets
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1. A historical perspective
Kepler’s laws
1.  The planets revolve on elliptical orbits around the Sun, with the
Sun in one focus.
2.  The area swept out by the radius vector from the Sun to the
planet per unit time is constant.
3.  The square of the orbital period T divided by the cube of the
mean distance from the Sun a is the same for all planets.
1.I The Sun as a star
The Sun as a star
Ancient greeks:
The Sun and the stars belong to the same category; they are stones
of fire.
1.I The Sun as a star
The Sun’s temperature
Surface temperature estimates:
To measure the Sun’s temperature, one needs to measure the total
energy received on Earth per surface area.
TSun = 4 x 106 K
(William Herschel, 1738-1822)
TSun = 1500-1800 K
(Claude Pouillet, 1838)
Solar constant
S = 1.76 cal cm-2 min-1
ice (insulation)"
glass
window"
thermometer"
opaque layer
with hole"
Today’s value of the Solar constant
S = 1.94 cal cm-2 min-1
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1.I The Sun as a star
The Sun’s temperature
Surface temperature estimates:
To measure the Sun’s temperature, one needs to measure the total
energy received on Earth per surface area.
TSun = 4 x 106 K
(William Herschel, 1738-1822)
TSun = 1500-1800 K
(Claude Pouillet, 1838)
TSun = 7338 K
(actinometer, begin of the 20th century)
1.I The Sun as a star
Spectroscopy
Joseph von Fraunhofer (1787-1826)
1.I The Sun as a star
Spectroscopy
Kirchoff’s laws (1959):
1.  A hot solid body produces a simple continuous spectrum without lines.
2.  A hot gas produces a spectrum with bright lines at discrete
wavelengths. The position and number of lines depends on the nature
of the gas.
3.  If a continuous spectrum shows dark lines, it originated from a hot
solid body surrounded by a gas that is cooler than the hot solid body
before reaching us. Again, the number and position of the dark lines
depends on the chemical nature of the surrounding cooler gas.
Planck’s law (1901):
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1.I The Sun as a star
The Sun and the Star’s
Diameter:
From eclipses measured to be RSun = 7 x 1010 m
Mass:
From planetary orbits using Kepler’s 3rd law MSun = 2 x 1033 g
⇒ Density ρ = 1.4 g/cm3
indicative of a gas ball
Spectroscopy:
•  The Sun is a gas ball.
•  Spectra enabled studies of the chemical composition of the Sun.
•  Spectra confirmed that stars are indeed other “Sun’s”.
Differences in spectra were attributed to different sizes, masses,
surface temperatures, chemical composition and most likely ages.
1.I The Sun as a star
Energy source of the Sun
Radioactive dating of Earth:
Age of Earth ~4.5 x 109 yr (begin 20th century)
Implication for the Sun and stars:
Stability over a very long timescale
Gravitational energy:
Nuclear fusion:
⇒ Lifetime of the Sun 1.03 x 1011 yr
1.II Models of Solar System Formation
Historical theories
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1.II Models of Solar System Formation
Historical theories
1.II Models of Solar System Formation
Historical theories
Kant 1724-1804
Laplace 1749-1827
1.II Models of Solar System Formation
Observed “solar nebulae”
Protoplanetary disks
Sizes: 50-few 100 AU
Masses: 0.1-0.001 M*
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1.II Models of Solar System Formation
Core accretion / gravitational
instability
Massive nebula (Cameron)
Low mass nebula (Safronov)
Mass: 0.1-1 M*
Mass: ~0.01 M*
Planets form like stars through
gravitational instabilities
Km-sized planetesimals form
through collisional accretion of
small dust
Planets form fast (~1000s of yr)
Planetary cores ~10 MEarth can
attract the surrounding gas and
form giant planets
Planets form slowly (~107-108 yr)
2. Observational Constraints
Regularity
AU
2. Observational Constraints
Regularity
•  Spin axis within
30o perpendicular
to the ecliptic
(except Uranus)
•  Prograde rotation
except Venus and
Uranus
AU
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2. Observational Constraints
Composition
Rocky planets
Gas and ice giants
Dwarf planets
2. Observational Constraints
Radioactive Dating & Deuterium
Meteorites:
4.55 x 109 yr
Chondrules:
4.56 x 109 yr
Rocks on Earth: 4.3 x 109 yr
Rocks on Moon: 4.4 x 109 yr
⇒ Sun and planets formed at the same
time (within 106 yr inside a few AU)
D/H ratios in the SS:
⇒ Planets formed from
interstellar matter
(D is rapidly destroyed
inside stars)
2. Observational Constraints
Dynamics of small bodies
[The Nice model: Gomes et al. 2005]
a)  Before Jupiter (green) and Saturn (yellow) reach their 2:1 resonance
b)  Scattering of planetesimals into inner Solar System when resonance
occurs
c)  After ejection of planetesimals (Uranus: cyan, Neptunus: blue)
Dynamics of small bodies carries imprint of early SS dynamics
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2. Observational Constraints
Minimum Mass Solar Nebula
[Desch 2007]
[Kuchner 2004]
3. How did the Sun form
Cosmic matter cycle
3. How did the Sun form
Molecular clouds
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3. How did the Sun form
Starless cores
Jeans radius:
3. How did the Sun form
Young stellar objects
Collapse phase:
[K band speckle interferometry, Preibisch]
free-fall phase ends when R~500 RSun
(for 1 MSun star)
Hayashi phase (vertical track)
3. How did the Sun form
Collapse
500 Msun
0.8 pc
tff = 190000 yr
t = 285000 yr
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3. How did the Sun form
Jets and outflows
3. How did the Planets form
Protoplanetary disks
gas
Dust
3. How did the Planets form
Planet formation
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3. How did the Planets form
Planet formation
500 AU
gas (?)
+
dust
gas
+
dust
100 AU
gas (?)
+
dust
100 AU
debris
disk
/
zodiacal
dust
3. How did the Planets form
Exoplanets
[Udry & Santos 2007]
Exoplanets from Kepler
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Exoplanets from Kepler
Compact systems, e.g. Kepler 11
3. How did the Planets form
Exoplanets
Planetary systems in
young debris disks
[Michaud & Macintosh 2008, Kalas et al. 2008,
Lagrange et al. 2009, Lafreniere et al. 2009]
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