The Evolution of Protoplanetary Disks and the
Diversity of Giant Planets
Extreme Solar Systems II
September 2011
Ben Bromley
Scott Kenyon
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Physics & Astronomy, University of Utah
Smithsonian Astrophysical Observatory
Fall 2011
Diversity of planets
the Solar System:
Is it extreme?
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Planet formation
theory and practice

Young stars: gas/dust disk

Coagulation and dynamics;
collisional accretion (many, small  few, large)


Debris disks are signposts
of planet formation
Massive cores accrete gas
(entrained debris helps, tGas ~ Myr)
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Planet formation:
difficulties

Dust-to-planetesimals
How do planetesimals grow from micron-sized dust?

Migration
How do planetary cores survive (fast, <Myr) migration?

Gas giant formation
How do gas giants grow as gas disks vanish?
Evolution of the gas disk is critical!
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Modeling disk evolution
•
Initial conditions
(Mdisk = 0.003—0.1 MStar; solid:gas ~ 0.01;
~ 1/a0.6—1.5)
•
Input physics
(alpha disk: a = 10-5—0.01; tDisk ~ 1/a ~ 1—10 Myr)
•
evolving the disk
(solve diffusion equation)

HSolid ~ √α

Timing is everything.
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Simulating planet formation
PLANETESIMALS:
pebbles—plutos
COAGULATION CODE
mergers, fragmentation
a-viscosity…
photoionization
FORMATION TIME:
0.1—1 Myr (cores)
1—10 Myr (J,N,SE)
10—100 Myr (Earths)
growing planetesimals
collisional cascade
N-BODY CODE
scattering, collisions
gas accretion
atmospheres (L,R)
migration
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
evolve gas, planetesimals, planets in concert
Growth of a planetary system
15
m / MEarth
semimajor axis (AU)
150
15
300
1000
10
Physics and Astronomy
University of Utah
log time (yr)
Extreme Solar Systems II
Fall 2011
cumulative fraction
Growth of planetary systems: Jupiters++ (> 1 MJupiter)
Physics and Astronomy
University of Utah
log semimajor axis (AU)
Extreme Solar Systems II
Fall 2011
cumulative fraction
Growth of planetary systems: Saturns (15 MEarth— 1 MJupiter )
Physics and Astronomy
University of Utah
log semimajor axis (AU)
Extreme Solar Systems II
Fall 2011
cumulative fraction
Growth of planetary systems: Earths++ (1—15 MEarth)
Physics and Astronomy
University of Utah
log semimajor axis (AU)
Extreme Solar Systems II
Fall 2011
cumulative fraction
Growth of planetary systems: planetary masses
Physics and Astronomy
University of Utah
log mass (MJupiter)
Extreme Solar Systems II
Fall 2011
of planets:
diskEarths+
properties
GrowthDiversity
of planetary
systems:
(1—15 MEarth)
cumulative fraction
initial disk mass (M)
Jupiters
(1—4)
(2—4)
(0—3)
(0—3)
(5—10)
Earths
(no gas giants)
log disk viscosity parameter (α)
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Results


Diverse systems of gas giants
in alpha-disk model
Predictions:
Multiplanet systems, ~MEarth—10’s of Mjupiter
High mass, low viscosity disks: Jupiters
Low mass, high viscosity disks: Neptunes, super-Earths

Next step: Include photoionization, migration….
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Simulation summary
photoionization
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Simulation summary
migration
photoionization
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Diversity of planets
Dynamics
(Architecture)
Planetary structure
(Radius – Mass, …)
Goal: consistent evolution of full system
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
Physics and Astronomy
University of Utah
Extreme Solar Systems II
Fall 2011
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