Ubiquity of planets and diversity of planetary systems: Origin and Destiny of multiple super Earths and gas giants.

Academia Sinica Institute of Astronomy and Astrophysics, Department of Physics, National University of Taiwan Dec 2, 2014

69 slides

Ubiquity of planets and diversity of planetary systems:

Origin and Destiny of multiple super Earths and gas giants.

Douglas N.C. Lin

Astronomy (UCSC), KIAA (PKU), IAS (THU)

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The unknown unknowns

Search for extra terrestrial intelligence (SETI)

3/69 Drake Equation

Radial velocity

Femtometer Doppler shift In individual lines

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Precision COSMOGONY

• Ubiquity of planets:

case study vs Science

• Diversity of systems:

realm of possibilities

• Population census

missing info & big picture

• Solar system connection Anthropic principle

Integral of details

Survival of fittest

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Transit (eclipse) searches

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Transit of Venus

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Conventional core accretion scenario

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Major Challenges:

• Retention of grains: m-size barrier (Whipple)

• Fragmentation: km-size barrier (Benz)

• Planetesimal-growth barrier: Isolation mass barrier (Wetherill)

• Gas accretion barrier: critical-mass cores (Cameron)

• Retention of cores: type I migration (Goldreich &

Tremaine, Ward)

• Retention of gas giants: type II migration (Lin &

Papaloizou)

• Multiple gas giants: rapid depletion of disk gas

• Competing physics on multiple length & time scales

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Step I: Meter-barrier Hydrodynamic drag on dusts

Zhang Yuan 12/69

Trapping locations: transition fronts and wall of magnetospheric cavity

9/59 Lecar asteroid 4417 13/69

Major Challenges:

• Retention of grains: m-size barrier (Whipple)

• Fragmentation: km-size barrier (Benz)

• Planetesimal-growth barrier: Isolation mass barrier (Wetherill)

• Gas accretion barrier: critical-mass cores (Cameron)

• Retention of cores: type I migration (Goldreich &

Tremaine, Ward)

• Retention of gas giants: type II migration (Lin &

Papaloizou)

• Multiple gas giants: rapid depletion of disk gas

• Competing physics on multiple length & time scales

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Planetesimal growth in a trap

Rixin Li, Yuan Zhang, Bili Dong

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Stalling of planets inside & at the magnetospheric truncation radius

Hartmann et al. 1998

Mass Accretion Rate Stellar Dipole Moment

16/69 Magnetosphere radius

Herczeg

Major Challenges:

• Retention of grains: m-size barrier (Whipple)

• Fragmentation: km-size barrier (Benz)

• Planetesimal-growth barrier: Isolation mass barrier (Wetherill)

• Gas accretion barrier: critical-mass cores (Cameron)

• Retention of embryos: type I migration (Goldreich &

Tremaine, Ward)

• Retention of gas giants: type II migration (Lin &

Papaloizou)

• Multiple gas giants: rapid depletion of disk gas

• Competing physics on multiple length & time scales

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Step III, oligarchic barrier: Isolation mass

Feeding zones: D ~ 10 r

Isolation mass: M

~ S

a

M

Kokubo & Ida

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Major Challenges:

• Retention of grains: m-size barrier (Whipple)

• Fragmentation: km-size barrier (Benz)

• Planetesimal-growth barrier: Isolation mass barrier (Wetherill)

• Proliferation of multiple, wide spread embryos

• Diversity of planetary architecture

• Retention of gas giants: type II migration (Lin &

Papaloizou)

• Multiple gas giants: rapid depletion of disk gas

• Competing physics on multiple length & time scales

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The planet exchanges angular momentum with:

- circulating fluid elements:

- librating fluid elements:

Maximum value scales with - gradient of disk vortensity (Ω/2Σ) across horseshoe region

Step IV, Embryos barrier: planetary migration Type I migration of super-Earth in isothermal disks

→ corotation torque

e.g. Goldreich & Tremaine (1980), Ward (1992) Masset (2001), Paadekooper, Baruteau, Kley

α = 0 α = 5x10^-5

α = 10^-2

Long-term evolution of the corotation torque is related to the disk viscosity Paardekooper, Baruteau,

→ differential Lindblad torque

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Planet-disk tidal interaction

Total tidal torque:

= f(p,q,p

,q

, p

, q

) G

p and q depend on disk structure &

p

,q

,p

, and q

also depend on m

(1/e)de/dt = (a/H)

(M

Sa

/M

) W

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Resonant sweeping of planetesimals

Major Challenges:

• Retention of grains: m-size barrier (Whipple)

• Fragmentation: km-size barrier (Benz)

• Planetesimal-growth barrier: Isolation mass barrier (Wetherill)

• Gas accretion barrier: critical-mass cores (Cameron)

• Retention of embryos: type I migration (Goldreich &

Tremaine, Ward)

• Retention of gas giants: type II migration (Lin &

Papaloizou)

• Multiple gas giants: rapid depletion of disk gas

• Competing physics on multiple length & time scales

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Core barrier: embryos’ resonant trapping

24/69 M=1Msun, Mdot = 10^-8M_sun/yr, a=10^-3

Beibei Liu

Loss of massive super-Earth embryos?

No shortage of building block materials

Major Challenges:

• Retention of grains: m-size barrier (Whipple)

• Fragmentation: km-size barrier (Benz)

• Planetesimal-growth barrier: Isolation mass barrier (Wetherill)

• Gas accretion barrier: critical-mass cores (Cameron)

• Retention of cores: type I migration (Goldreich &

Tremaine, Ward)

• Retention of gas giants: type II migration (Lin &

Papaloizou)

• Multiple gas giants: rapid depletion of disk gas

• Competing physics on multiple length & time scales

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Radiation transfer & gas accretion

• Is there a threshold mass for gas accretion? Gas accretion barrier:

Klahr Pollack et al

Ikoma

Bypass the resonance barrier

Orbit crossing, close encounters, home coming & collisions 27/69

Giant impacts of super Earths

Liu Shangfei 28/69

Major Challenges:

• Retention of grains: m-size barrier (Whipple)

• Fragmentation: km-size barrier (Benz)

• Planetesimal-growth barrier: Isolation mass barrier (Wetherill)

• Availability of building block material

• Frequency of planets around different type stars

• Retention of gas giants: type II migration (Lin &

Papaloizou)

• Multiple gas giants: rapid depletion of disk gas

• Competing physics on multiple length & time scales

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Dependence on stellar mass

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Dependence on the disks’ accretion rate

Mdot = 10^-8 5 x10^-8 10^-7

2M_sun

1M_sun

0.5M_sun

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Dependence on the disks’ accretion rate

1) Cores’ migration speed is determined by the surface density of the disk gas.

2) Surface density of the disk gas

is proportional to the gas accretion rate 3) Gas accretion is observed to increase with the host stars’ mass.

4) Gas giants’ frequency correlation with the host stars’ mass is through mdot.

Cores enter orbit crossing zone 0.5M_o

2M_o

Resonant barrier

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Planetary mass & size vs stellar metallicity

There is a strong correlation between h

vs stellar metallicity.

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Abundance of super Earths

There is no shortage of super Earths around metal-poor stars

Formation of super Earths Does not depend on Z or M

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Dependence on metallicity

Fe/H=1 Fe/H=3

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Migration in metal-rich disks

Fe/H=1/3

Fe/H=1/3

Fe/H=3

Fe/H=3

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Importance of snow line

10^-8M_o yr^-1 6 x 10^-8M_o yr^-1 37/69

Major Challenges:

• Retention of grains: m-size barrier (Whipple)

• Fragmentation: km-size barrier (Benz)

• Planetesimal-growth barrier: Isolation mass barrier (Wetherill)

• Gas accretion barrier: critical-mass cores (Cameron)

• Retention of cores: type I migration (Goldreich &

Tremaine, Ward)

• Retention of gas giants: type II migration (Lin &

Papaloizou)

• Multiple gas giants: rapid depletion of disk gas

• Competing physics on multiple length & time scales

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Giant impacts and mergers

Liu Shangfei Zhou Jilin

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Enhanced formation of multiple planets

40/69 BeiBei Liu

XiaoJia Zhang

Grand design barrier: dynamical instability

• How did gas giants acquire their eccentricity?

Bryden

Jilin Zhou 41/69

Dynamical diversity

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Gas giants’ type II migration

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Beibei Liu

Core barrier: embryos’ resonant trapping

• Long term evolution: largest cores formed early

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Period distribution of hot Jupiters:

Dependence on stellar metallicity

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Smoking gun for core accretion (KOI 94)

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Planets’ size-period distribution from the Kepler surveys

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Type I migration with evolving disk

Transiting location move inward

Mass region corresponds to outward decrease slightly

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A

2 Earth Jupiter

½ Earth

5 Earth

r

r

r

Hot Jupiters park Closer than

Super Earths

Kretke

Gas giants SuperEarths

Neptunes

Sub/warm Earths

Super Earths: some key issues

• How to differentiate type I and II migration?

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Rai Xu, Wendy Ju

51/69 Zhuoxiao Wang Beibei Liu

New Candidate Catalog (Batalha et al. 2012) What can we learn from Multiple systems !!!

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How compact can multiple systems be?

Kevin Schlaufman Xiaojia Zheng

Stability and coplanarity

Random pairings

7.6% would be unstable x 742 pairs

= 56 unstable pairs

53/69 Fabricky

Super Earths: some key issues

• Did planets capture each other and parted their ways?

Exit resonances

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diverse migration mechanisms

Resonant capture Collisional damping Gas drag

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RM effect and challenge to migration

56/69 Liu, Guillichon

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Gas giants: some key issues

• Is there evidence for M _* -dependent tidal dissipation?

Winn

Misaligned magnetosphere

Lai, Foucart, & Lin

Similar effects in close-in planets: additional Torque and dissipation avenues

Cumming & Lin Observable tests

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Alternative model: internal gravity wave

Tami Rogers 559/69

Gravity waves in intermediate-mass stars

60/69 Tami Rogers

Tami Rogers

Gas giants: some key issues

• Is there evidence for internal differential rotation ?

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62/69 Laine, De Colle

Inside the stellar magnetosphere

Inside the super Earths

Saur et al 63/69 B. Dai, Y.Z. Niu, R. Laine

Super Earths’ geology & atmosphere

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Other issues

Late-stage evolution in debris disks Post formation dynamical evolution Non planar planetary systems

Planets around different mass stars

The role of elemental differentiation in natal disks Planets in binary stars

Planets around stars in clusters

Planets’ magnetic and tidal interaction with their host stars Planets’ consumption by their host stars

Planets’ survival around evolved stars Planets’ internal structural evolution Planets’ atmospheric dynamics

How is habitability affected by dynamical interaction between planets

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Updated version of population synthesis models

66/69 Ida

67/69 Cosmographia 1544

Summary

• Planet formation is a robust process and their dynamical architecture is diverse.

• Planetary origin and destiny are determined largely by the structure & evolution of the disks.

• Migration due to planet-disk interaction played a big role in the asymptotic properties of the planets.

• Theory of planetary astrophysics is relevant to many other astrophysical contexts.

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``there are infinite worlds both like and unlike this world of ours …’’

Epicurus