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The formation of stars and planets
Day 5, Topic 3:
Migration of planets
and
Outlook...
Lecture by: C.P. Dullemond
Three types of migration
• Type I: low mass planets
• Type II: high mass planets
• Type III: rare type II variant
Type I migration
•
•
Planet’s gravity launches spiral waves in disk
These spiral waves exert torque on planet:
– Inner spiral wave pushes planet outward
– Outer spiral wave pushes planet inward
•
Outer spiral wave wins: inward migration
QuickTime™ and a
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are needed to see this picture.
Type I migration
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by Frederic Masset
www-star.qmul.ac.uk/~masset/
Type I migration
Time scale of inward type I migration (1 solar mass star):
1
1
1/ 2
2









M
r
h /r
gas
tType I  10 4 ...10 5 
 
 years
 
2  
10M   100g/cm  AU  0.07 
Review Thommes & Duncan in “The
Formation of Planets” 2005
3-D estimates: 105...106
(Tanaka et al. 2002)
Gap opening
Hill sphere: sphere of gravitational influence of planet:
 M 
rHill  
 r
3M* 
1/ 3
If Hill radius larger than h of disk: disk can be regarded as
 thin compared to potential. This happens for massive
enough planets.
Planet will affect structure of the disk.
P. Ciecielag
Effective potential, Lagrange points
r1
r1 M 2

r2 M1
r2
L4

Effective potential in the
co-rotating frame:
eff
GM1 GM2 1 2 2


 K r
r  r1 r  r2 2
centrifugal
kinetic
energy
L3
L1
L5
Example: M2/M1=0.1
L2
Effective potential, Lagrange points
r1
r1 M 2

r2 M1
r2
L4

Effective potential in the
co-rotating frame:
eff
GM1 GM2 1 2 2


 K r
r  r1 r  r2 2
centrifugal
kinetic
energy
L3
L1
L5
Example: M2/M1=0.01
L2
Trojans of Jupiter
Motion of gas / particles in horseshoe
Gap opening
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Dekompressor „YUV420 codec“
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by Frederic Masset
www-star.qmul.ac.uk/~masset/
Type II migration
• Massive planet opens a gap
• Accretion in the disk is stopped by the gap
– If the disk is massive enough: accretion continues,
simply by pushing the planet inward. Planet is locked to
the disk accretion. Type II migration
– If the disk is not massive enough: planet will not
migrate. Inner disk will deplete.
• Three-dimensional models: accretion can still
proceed somewhat by flowing in 3-D past the
planet.
Transition from I to II and gap opening
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by Frederic Masset
www-star.qmul.ac.uk/~masset/
Type III migration (run-away migration)
Masset & Papaoloizou
Type III migration (run-away migration)
Masset & Papaoloizou
Type III migration (run-away migration)
• If planet initially moves inward:
– Some inner disk material enters horseshoe, gets flung
to outer orbit of horseshoe by planet. Planet loses
angular momentum.
– Some horseshoe material enters outer disk, does not
get flung back to inner orbit of horseshoe.
– Netto: one-sided asymmetric angular momentum
transport from planet to disk: inward push! Run-away!
• If planet initially moves outward: Same thing, but
the other way: planet is pushed outward. Also runaway!
Type III migration (run-away migration)
Zur Anzeige wird der QuickTime™
Dekompressor „YUV420 codec“
benötigt.
by Frederic Masset
www-star.qmul.ac.uk/~masset/
Note: this
movie has
opposite
rotation as
discussion
above.
Why do planets exist everywhere?
• Migration should have depleted all planets
• What about bandwagon approach (form planets
all the time, lose most of them via migration, but
when disk dissipates some are left)?
– Problem: Need plenty of solid disk material to form a
planet
– Problem: First make rocky core, then accrete gas. This
process takes longer than migration time scale.
• Problem of migration is one of main open
questions of planet formation!
How to planets get in resonance?
G. Bryden
Stopping migration with a resonance
Masset & Snellgrove
Outlook
Outlook
• Field of star- and planet formation more lively than
ever!
• New telescopes give us unprecedented view of
disks:
–
–
–
–
Spitzer Space Telescope (infrared)
Very Large Telescope interferometer (infrared)
ALMA (submillimeter) >= 2010
Herschel (far-infrared) >= 2007
• Theory/lab:
– Computers are now powerful enough to model the
growth from dust to planets
– Laboratory experiments measure sticking and collision
properties of particles
Outlook
Very Large
Telescope:
Infrared
Interferometry
Resolving the
earth forming
regions of
disks
(in operation)
Outlook
Herschel Space Observatory (far-infrared/submillimeter)
Looking for water in extrasolar (pre-)planetary systems
Outlook
Atacama Large Millimeter Array (ALMA)
Chemistry, small scale disk structure, large grain dust population
Outlook
• Planet-hunting is hot!
– Space missions will even be able to detect Earth-like
planets! DARWIN / TPF
– We may even analyze their atmospheres!!! (life??)
Outlook
Darwin/TPF: hunting for other ‘Earths’
Outlook
Detection of possible life on extrasolar Earth-like planets