Great Migrations

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UTSC
Planetary science and disks 1. dusty disk
instabilities 2. migration of protoplanets
Prof. Pawel Artymowicz, Lecture 17 ASTC25
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Astronomy and Astrophysics - whats its
purpose in the society? 0. Model for freedom of
thinking cooperation 1. Understanding - solar
system functioning and origin - extrasolar
planets, and the place of solar system among
other systems - sun-Earth connection - chaos
2. Prediction - global warming - impacts
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• Understanding of extrasolar and solar planetary
  systems through theory of their formation
• Introducing extrasolar systems
• Protoplanetary disks
• Disk-planet interaction resonances and torques,
  numerical calculations, mass buildup, migration
  of planets
• Dusty disks in young planetary systems
• Origin of structure in dusty disks

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HD107146
Source P. Kalas
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At the age of 1-10 Myr the primordial solar
nebulae protoplanetary disks T Tau accretion
disks undergo a metamorphosis
A silhouette disk in Orion star-forming nebula
Beta Pictoris
They lose almost all H and He and after a brief
period as transitional disks, become low-gas
high-dustiness Beta Pictoris systems (Vega
systems).
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Prototype of Vega/beta-Pic systems
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B Pic b(?) sky?
Beta Pictoris
11 micron image analysis converting observed
flux to dust area (Lagage Pantin 1994)
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Chemical basis for universality of
exoplanets cosmic composition (Z0.02
abundance of heavy elem.) cooling sequence
olivines, pyroxenes dominant, (MgFeSiO),
then H2O
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Hubble Space Telescope/ NICMOS infrared camera
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HD 141569A is a Herbig emission star gt2 x solar
mass, gt10 x solar luminosity, Emission lines of H
are double, because they come from a rotating
inner gas disk. CO gas has also been found at r
90 AU. Observations by Hubble Space
Telescope (NICMOS near-IR camera).
Age 5 Myr transitional disk
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HD 14169A disk (HST observations), gap
confirmed by the new observations
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HD 141569A Spiral structure detected by
(Clampin et al. 2003) Advanced Camera for Surveys
onboard Hubble Space Telescope

• Gas-dust coupling?
• Planetary perturbations?
• Dust avalanches?

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Radiation-pressure instability of opaque disks
found at UTSC
r
r
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Radial-velocity planets

• around normal stars

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-450 Extrasolar systems predicted (Leukippos,
Demokritos). Formation in disks -325 Disproved
by Aristoteles 1983 First dusty disks in
exoplanetary systems discovered by IRAS 1992
First exoplanets found around a millisecond
pulsar (Wolszczan Dale) 1995 Radial
Velocity Planets were found around normal, nearby
stars, via the Doppler spectroscopy of the host
starlight, starting with Mayor Queloz,
continuing wth Marcy Butler, et al.
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Orbital radii masses of the extrasolar planets
(picture from 2003)
Radial migration
Hot jupiters
These planets were found via Doppler
spectroscopy of the hosts starlight. Precision
of measurement 3 m/s
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Marcy and Butler (2003)
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2005
2003
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Like us? NOT REALLY
Why?
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Diversity of exoplanetary systems likely a result
of disk-planet interaction a m? (low-medium)
e planet-planet interaction a m? (high)
e star-planet interaction a m e disk breakup
(fragmentation into GGP) a m e?
metallicity
X
X
X
X
X
X
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Disk-planet interactionobservation numerics
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A gap-opening body in a disk Saturn rings,
Keeler gap region (width 35 km) This new 7-km
satellite of Saturn was announced 11 May 2005.
To Saturn
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Masset and Papaloizou (2000) Peale, Lee (2002)
Some pairs of exoplanets may be caught in a 21
resonance
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Mass flows through the gap opened by a
jupiter-class exoplanet
----gt Superplanets can form
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An example of modern Godunov (Riemann solver)
code PPM VH1-PA. Mass flows through a wide
and deep gap!
Surface density Log(surface density)
Binary star on circular orbit accreting from a
circumbinary disk through a gap.
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simulation of a Jupiter in a standard solar
nebula. PPM
( Artymowicz 2004)
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What permeability of gaps teaches us about our
own Jupiter - Jupiter was potentially able to
grow to 5-10 m_j, if left accreting from a
standard solar nebula for 1 Myr - the most
likely reason why it didnt the nebula was
already disappearing and not enough mass was
available.
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Disk-planet interactionnew strange
migrationmode
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Migration Type I embedded in fluid
Migration Type III partially open (gap)
Migration Type II in the open (gap)
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Type I-III Migration of protoplanets/exoplanets
Timescale

• Disks repel planets
• Type I (no gap)
• Type II (in a gap)
• Currently THE problem is how not to
  lose planetary embryos (cores) ?

Ward (1997)
I
II
M/M_Earth
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Type I-III Migration of protoplanets/exoplanets
Timescale

• If disks repel planets
• Type I (no gap)
• Type II (in a gap)
• If disks attract planets Type III
• Qs
• Which way do they migrate?
• How fast?
• Can the protoplanets survive?

....III..
I
II
M/M_Earth
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Variable-resolution PPM (Piecewise Parabolic
Method) Artymowicz 1999 Jupiter-mass
planet, fixed orbit a1, e0. White oval
Roche lobe, radius r_L 0.07 Corotational
region out to x_CR 0.17 from the planet
disk
gap (CR region)
disk
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Consider a one-sided disk (inner disk only). The
rapid inward migration is OPPOSITE to the
expectation based on shepherding (Lindblad
resonances).
Like in the well-known problem of sinking
satellites (small satellite galaxies merging
with the target disk galaxies), Corotational
torques cause rapid inward sinking. (Gas is
trasferred from orbits inside the perturber to
the outside. To conserve angular momentum,
satellite moves in.)
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Now consider the opposite case of an inner hole
in the disk. Unlike in the shepherding case, the
planet rapidly migrates outwards.
Here, the situation is an inward-outward
reflection of the sinking satellite problem.
Disk gas traveling on hairpin (half-horeseshoe)
orbits fills the inner void and moves the planet
out rapidly (type III outward migration).
Lindblad resonances produce spiral waves and try
to move the planet in, but lose with CR torques.
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Outward migration type III of a
Jupiter Inviscid disk with an inner clearing
peak density of 3 x MMSN Variable-resolution, ad
aptive grid (following the planet). Lagrangian
PPM. Horizontal axis shows radius in the range
(0.5-5) a Full range of azimuths on the vertical
axis. Time in units of initial orbital period.
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Edges or gradients in disks Magnetic cavitie
s around the star Dead zones
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Summary of type-III migration

• New type, sometimes extremely rapid (timescale
  lt 1000 years). CRs gtgt LRs
• Direction depends on prior history, not just on
  disk properties.
• Supersedes a much slower, standard type-II
  migration in disks more massive than planets
• Very sensitive to disk density gradients.
• Migration stops on disk features (rings, edges
  and/or substantial density gradients.) Such edges
  seem natural (dead zone boundaries,
  magnetospheric inner disk cavities,
  formation-caused radial disk structure)
• Offers possibility of survival of giant planets
  at intermediate distances (0.1 - 1 AU),
• ...and of terrestrial planets during the passage
  of a giant planet on its way to the star.
• If type I superseded by type III then these
  conclusions apply to cores as well, not only
  giant protoplanets.

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1. Early dispersal of the primordial nebula gt
no material, no mobility 2. Late formation
(including Last Mohican scenario)