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Star and Planet formation

Carsten DominikUniversity of Amsterdam, 2011

Main Books:

• Main Books– S.W. Stahler & F. Palla, “The formation of stars”– P. Armitage: “Astrophysics of Planet Formation”

• Additional Books– L. Hartmann, “Accretion processes in star

formation”– I. Pater & J. Lissauer: Planetary Physics– Protostars and Planets II, III, IV, (V)

• Thanks– Kees Dullemond, Ewine van Dishoek, Rens

Waters, Inga Kamp, and many others.

Syllabus

We use the Syllabus Inga Kamp and MarcoSpaans have written. I am modifying andupdating it throughout the course

• online www.astro.rug.nl/~kamp - Lectures• Updated version and new chapters

– www.astro.uva.nl/~dominik/Teaching/SPF

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Projects• Numerical integration of Bonner Ebert sphere• BPCA cluster formation• Numerical study of Disk stirring• Numerical study dust growth by settling and radial

drift.• Review paper summaries (30 min talk)‒ Nice model as constraint for solar system (Gomez et al2004)

‒ Irregular moons of major planets (Jewitt &Haghighipour 2007)

‒ Exoplanet statistics overview (Udry & Santos 2007)– Short-lived radio nuclides and relative timing of SS formation

(Dauphas & Chaussidon 2011)

Course outline I

1. Overview and Introduction, Properties ofstars and the solar system (what are wetrying to understand?). Start with MolecularCloud properties

2. Molecular clouds, core, observationalproperties. Molecules as tracers ofproperties and evolution.

3. Cloud cores, stability and collapse4. Pre-main-sequence stars5. High mass star formation: Clusters

Course outline II

6. Circumstellar disks: Viscous accretion7. Circumstellar disks: Irradiation8. Dust motion and aggregation in disks9. Planetesimals and further growth to terrestrial

planets10. Giant planet formation: Gravitational instability

versus core-accretion11. Chemical evolution from molecular clouds to

planets12. Comets, asteroids and debris disks13. Extrasolar planets, Planet Migration and further

puzzles.

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The geocentric model

Before 16th century• the geocentric model

was everywhere• Aristarchos of

Samos (280BC) hadsuggested aheliocentric model

• Even Tycho Braherejected it becauseof not parallaxesobserved (<=0.77”for Proxima Cen)

The heliocentric model

Nicolaus Copernicus (1473 - 1543)

The heliocentric model

Johannes Kepler (1571 - 1630)

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Keplers laws

1. The planets revolve onelliptical orbits, and theSun is located in onefocal point

2. The area swept out bythe radius vector fromthe Sun to the planet perunit time is constant

3. The square of the orbitalperiod T divided by thecube of the semi majoraxis a (= mean distance)is the same for allplanets

!

dAdt

=12r2 d"dt

#

$ %

&

' (

!

T 2

a3=

4"G M# +mpl( )

The planets

zon

Diameter Earth = 12.756 km

Size to scale

Mer

cury

Venu

sEa

rthM

ars

Jupi

ter

Satu

rn

Uran

us

Nept

une

Plut

o

1,00,4 0,9 0,5 11 9 4 4 0,2

1101781

1846

The planets

zon

Units = 150.000.000 km = 1 AU

Distance to scale

Mer

cury

Venu

sEa

rthM

ars

Jupi

ter

Satu

rn

Uran

us

Nept

une

Plut

o

1,0

0,4

0,71,5

5,2 20 30 409,6

asteroïden

}

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Kinds of planets

zone 1

zone 2

zone 3

Zone 1: earth-like

Zone 2: Gasgiants

Zone 3: icy bodies

asteroïden

Earth-like planets

Properties: • Silicates• rather small (4.000 - 13.000 km Ø)• High densities (3 - 5,5 gram/cm-3)

0,4 0,9 1,0 0,5

The Gas giants

Properties: • Lots of gas and ice• rather large (50.000 - 140.000 km Ø)• low densities (0,6 - 1,6 gram/cm-3)

11 4,0 3,99,2

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Orbits

40 AE

Pluto

NeptuneUranus

Saturn

Jupiter

Asteroids

Mars

Directi

on o

f rot

ation

Orbits in one plane

40 AE

PlutoNeptunus

Uranus

Saturnus

Jupiter

Mars

Direction of rotation

Radioactive dating, Isotopes• 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 few x106 yr inside a few AU)

• D/H ratios in the SS:!Planets formed frominterstellar matter (D is rapidlydestroyedinside stars)

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Isotopes

• D/H ratios in the SS:!Planets formed frominterstellar matter (D is rapidlydestroyedinside stars)

• Oxygen isotopes:! Severalsources of oxygen have beenmixed in the Solar System,e.g. Gas, ice, and solid forms

Dynamical constrains: small bodies

• Before Jupiter (green) and Saturn (yellow) reach their 2:1resonance

• Scattering of planetesimals into inner Solar System whenresonance occurs

• After ejection of planetesimals (Uranus: cyan, Neptunus: blue)Dynamics of small bodies carries imprint of early SS dynamics

The Nice model (Gomez et al 2005)

Main properties of the solar system I• Orbits of major planets are almost circular, almost co-

planar, almost in the equatorial plane of the Sun.• Orbits of major planets are confined to <30AU. They

don’t cross, don’t even come close• Little debris except asteroid Belt, Jupiters Trojans,

Kuiper Belt. Regions between planets are unstable.• 1012 comets in Oort clouds.• Rotation of 6 planets along with orbital motion, but

Venus, Uranus and Pluto rotate retrograde.• Most planets have natural satellite systems, on low

inclination, low eccentricity orbits. Distant smallmoons can have all kinds of orbits.

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Main properties of the solar system II• Planetary masses account for less than 0.2% of the

solar system, dominated by far by Jupiter and Saturn.Asteroids and KB Comets are minor contributions tomass.

• The planets carry 98% of the angular momentum inthe system.

• Rocky planets close to the Sun, Gas planets between5 and 10AU, ice planets (including Uranus andNeptune) further out.

• Ages 4.56Gyr for the oldest rocks. Differentiatedrocks at 4.4-4.56Gyr, Lunar surface 3.1-4.4Gyr.

• Isotopically well mixed, even though elementabundance vary greatly throughout the system.

• Cratering record talks about much higher impactrates before 3.8Gyrs ago.

Exoplanets

Origin of Life

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A brief history...

• 1755: Kant postulates that solar system formed from‘Urnebel’ (‘solar nebula’)

• 18th-19th: Observations of dark clouds• 1904: Hartmann: Discovery of interstellar gas• 1930: Trumpler: Discovery of interstellar dust• 1944: von Weizsäcker forwards idea that planets formed in

vortices in a turbulent protoplanetary disk (=solar nebula)• 1952: Lüst develops first real theory of pp accretion disk• 1960-70’s: Mapping of interstellar clouds (HI 60’s, CO: 70’s)• 1961: Hayashi: first theory of pre-main sequence evolution• 1969: Safronov published theories of accumulation of solid

particles and planet formation (most of his theories are stillhighly relevant today!)

• 1977: Shu: first theory of cloud collapse

A brief history...

• 1980’s: IRAS satellite maps at 12, 25, 60 and 100 µm:discovery of many young stellar objects (YSOs).

• 1984/1987: Lada & Wilking, Adams, Shu & Lada: YSOclassification and evolutionary sequence (class I, II, III).

• 1984: Auman et al., Smith & Terrile: discovery of disksaround mature main-sequence A stars (Vega, "-Pic).

• Late 80s/early 90s: Infrared and sub-mm observatories:indirect evidence of disks.

• Mid 90s: Hubble images of disks: direct evidence for disks• 1995/1996: Mayor & Queloz (1995), Marcy & Butler (1996):

discovery of extrasolar planets around solar type stars• >1995: Explosion of research on disks and extrasolar

planets.

Historical theories

1.II Models of Solar System Formation

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Historical theories

1.II Models of Solar System Formation

Historical theories

1.II Models of Solar System Formation

Kant 1724-1804

Laplace 1749-1827

Overview: The egg nebula

EagleNebula(M16)

Picture credit: T.A. Rector & B.A. Wolpa

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Detail of Eagle Nebula: HST

Chameleon molecularcloud:

example of low mass starforming region

No star formation in Barnard 68

Optical multi-colourOptical multi-colourimageimage

Optical-IR multi-colourOptical-IR multi-colourimageimage

((Alves Alves et al.)et al.)

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Initial mass function

Hydrodynamic simulations

Proto-planetary disks

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‘Isolated’ Star Formation

M.Hogerheijde1998, after Shu et al. 1987

Planets form in the disk (?)

Artist’s impression of planet formation...

Grinding asteriods back to dust...

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BetaPictoris:

Debris Disk