the search for habitable planets and the quest to understand their origins d.n.c. lin kiaa, peking...
TRANSCRIPT
The search for habitable planets andthe quest to understand their origins
D.N.C. Lin KIAA, Peking University,University of California, Santa Cruz,
Kavli Institute for Theoretical Physics China Beijing, China May 26th, 2007
30 slides
High-precision spectroscopy
2/30
Mass-period distribution
A continuous logarithmic period distributionA pile-up near 3 days and another pile up near 2-3 yearsDoes the mass function depend on the period?Is there an edge to the planetary systems?Does the mass function depend on the stellar mass or [Fe/H]?
3/30
Avenues of planet formation
4/30
Hillenbrand & Meyer 2000
Inner disks disappear ~ 10 Myr
Per
Pleiades Hyades
Ursa Major
TW Hyd
N2264
IC 348
L1641bLupus
Cha
ONC
N7128
LH101
Taurus
L1641y
Mon R2
N1333
CrA
Trap
N2024
Oph
0.1 1 10 100 1 Gyr
Age (Myr)
0.0
0.2
0.4
0.6
0.8
1.0Fr
act
ion
of
dis
ks
5/30 Gas accretion rate
Chondritic meteorites
1) Limited size range, sm-cm,2) Glass texture, flash heating, 3) Age difference with CAI’s,4) Matrix glue & abundance,5) Weak tensile strength.6) Formation timescale 2-3 Myr 6/30
7/30
Feeding zones: 10 rHill
Isolation mass:Misolation ~ a3
From planetesimals to embryos
Initial growth: (runaway)
8/30
type-II migration
planet’s perturbation
viscous diffusion
type-I migration
disk torque imbalance
MyrAU1
05.023
23
*
g
SNg,Imig,
a
M
M
M
M
op
MM )10010( MM )11.0(
MyrAU1
10
2
12
1
*
o3
J
p
g
SNg,IImig,
a
M
M
M
M
Disk-planet tidal interactions
viscous disk accretion
Goldreich & Tremaine (1979), Ward (1986, 1997), Tanaka et al. (2002)
Lin & Papaloizou (1985),....
9/30
(Mass) growth vs (orbital) decay
Loss due to Type I migrationJovian-mass ESP’s are rare aroundlate-type stars
MyrAU1)(
)0(04.0
*
o
g
gImig,
43
a
M
M
t
Embryos’ migration time scale
511
AU1)0(
)(
g
g
Imig,
embryo
at
Outer embryos are better preserved only after significant gas depletion
Critical-mass core:Mp=5Mearth
MyrAU1)(
)0(01.0
23
21
*
g
gImig,
a
M
M
t o
10/30
Dependence on M*
1) J increases with M*
2) Mp and ap increase with M*
Do eccentricity and multiplicity depend on M*? 11/30
Planetary interior:diverse structure & Fe/H
HD149026b: 67 earth-mass core
12/30
Giant impacts1) Diversity in core mass2) Spin orientation3) Survival of satellites4) Retention of atmosphere
13/30Late bombardment of planetesimals
The period distribution:Type II migration
Disk depletion versus migration14/30
Stellar metallicity, mass loss, & circularization of hot Jupiters
1) Early formation2) Extensive migration3) High mortality rate4) Planetary mass loss5) Tidal circularization
6) Signs of evolution?
15/30
short-period cutoffStopping mechanisms: 1) magnetospheric cavity 2) stellar tidal barrier 3) protoplanetary consumption4) planetary tidal disruption
Prediction: 90% disruption of hot JupitersBimodal Q*: prevalence of 1-day planets
Ogilvie
Tidal inflationBodenheimer
16/30
Transits: atmosphere & structure
29/48
17/30
period cutoffs
depletion vs growth time
Ice giants:Collisions vs ejections
Prediction: period fall-offTest: gravitational lense
18/30
Multiple systems
Diversity in mass distributionResonant system with limited massWhat fraction of Jovian mass planets reside in multiple systems?Is multiplicity more correlated with [Fe/H] or M* than single planets?
19/30
Multiple planets
a) Induced formation of multiple giantsb) Resonant planetsc) Formation time scalecomparable to migration
Bryden
20/30
Post Depletion Dynamical Stability Dynamical filling factor: e excitation & chaos
21/30 Rayleigh distribution
Migration-free sweeping secular resonances
Resonant secularperturbationMdisk ~Mp
(Ward, Ida, Nagasawa)Ups And
Transitional disks
22/30
Sweeping secular resonance in ESP’s
Excitation of e & tidal inflation in HD209458 &disruption in 55 Can Gu, Ogilvie, Bodenheimer, Laughlin
Rotational flattening & precession Nagasawa, Mardling
Triple system around Ups And
23/30
Mean motion resonance capture
Tidal decay out of mean motion resonance(Novak & Lai)
Impact enlargementRejuvenation of gas Giant. HD 209458b(Guillot)
Detection probability of hot Earth Narayan, Cumming
Migration of gas giants can lead To the formation of hot earthImplication for COROT
Zhou
24/30
Dynamical shake up (Nagasawa, Thommes)Bode’s law: dynamically porous terrestrial planetsorbits with low eccentricities with wide separation
25/30
Migration, Collisions, & damping
1. Clearing of the asteroid belt2. Earlier formation of Mars3. Sun ward planetesimals
A. Late formation (10-50 Myr)B. Giant-embryo impacts C. Low eccentricities, stable orbits
26/30
Giant impact & lunar formation1) Lunar material similar to the Earth’s crust.2) Formation after the differentiation (30 Myr)3) Mars-size impactor4) Post impact circular orbit
Formation after 60 Myr
Formation on 30-60 Myr27/30
Last melting events of chondrules
Flash heating:Large : evaporationMedium : meltingSmall : preservation
28/30
Frequency of Earth
29/30
Sequential accretion scenario summary1) Damping & high leads to rapid growth & large isolation masses. Jupiter formed prior to the final assemblage of terrestrial planets within a few Myrs.2) Emergence of the first gas giants after the disk mass was reduced to that of the minimum nebula model. 3) Planetary mobility promotes formation & destruction.4) The first gas giants induce formation of other siblings. 5) Shakeup led to the dynamically porous configuration of the inner solar system & the formation of the Moon.6) Earths are common and detectable within a few yrs!
30/30
Dependence on the stellar [Fe/H]
Santos, Fischer & Valenti
Frequency of Jovian-mass planets increases rapidly with [Fe/H].But, the ESP’s mass and period distribution are insensitive to [Fe/H]!Is there a correlation between [Fe/H] & hot Jupiters ?Do multiple systems tend to associated with stars with high [Fe/H]?
4/43
Disk evolution
6/43
Protostellar disks:Gas/dust = 100
Dabris disks:Gas/dust = 0.01
only external disk but accreting star
Transitionaldisks
From dust to planetesimals
Retention of heavy elements:growth~dust but decay ~ gas 6a/43
Potential observational signatures
Coexistence of gas and solid phase volatile icesEvolution of snow line
8/43
Condensation sequence
Meteorites:Dry, chondrules& CAI’s
Icy moons 9/43
Signs of Crystalline grains
Bouwman Apai
8a/43
Growth during gas depletion
Rapid damping: many small residual embryos. Slow damping: large eccentricity
Delicate balance: Kominami & Ida
Separation of eccentricityExcitation and damping is Needed!
12/43
Competition: M growth & a decay
Hyper-solar nebulax30
Metal enhancement does not always help! need to slow down migration
10 Myr 1 Myr0.1 Myr
Limiting isolationmass
13a/43
Embryos’ type I migration (10 Mearth)
Cooler and invisic disks
Warmer disks14/43
Accretion onto cores
Challenges:1) Core growth: perturbation slowdown & planetesimal gaps (Ida)2) Radiation transfer efficiencygrain survival & opacity (Podolak)3) Low global dust (Bryden)
Pollack et al
Bodenheimer
Korycansky
18/43
Flow into the Roche lobe
Bondi radius (Rb=GMp /cs2)
Hill’s radius (Rh=(Mp/3M* )1/3 a)Disk thickness (H=csa/Vk)
Rb/ Rh =31/3(Mp /M*)2/3(a/H)2
decreases with M*
21/43
H/a=0.07
H/a=0.04
Preferred cradles of gas giants: snow line
Limited by:Isolation slow growth
17/43
Effect of type I & II migration
22/43
Habitable planets
M/s accuracy
The mass distribution
Origin of desert:Runaway gas accretion
Bryden
28/43
Metallicity dependence
[Fe/H]
Two determining factors for the slope:1) Heavy element retention efficiency, growth vs accretion2) Growth rate and isolation mass of embryos
29/43
Stellar mass-metallicity
30/43
More data needed for highand low-mass stars
Sweeping clear of planetesimals
Sweeping secularresonance & gas drag Pic:Duncan, Nagasawa
37a/43
Formation of warm Neptunes
Jupiter-Saturn secular interaction& multiple extrasolar systems
Relativistic detuning in Arae39/43
A 2 Mearth “hot rock” planet in a 7-d orbit observed for 6 months with APF @ 1.3 m/s
precision
Easily detected!Easily detected!
But this short-period planet But this short-period planet is is muchmuch too hot for habitability too hot for habitability
40a/43
1 Mearth planet in a 35-d habitable-zone orbit around a nearby M dwarf – observed for 6 months with a 9-
telescope global array @ 2.0 m/s precision
Easy detection!Easy detection!
42/43
Outstanding issues:
1) Frequency of planets for different stellar masses2) Completeness of the mass-period distribution3) Signs of dynamical evolution4) Mass distribution of close-in planets: efficiency of migration5) Halting mechanisms for close-in planets6) Origin of planetary eccentricity7) Formation and dynamical interaction of multiple planetary systems8) Internal and atmospheric structure and dynamics of gas giants9) Satellite formation10) Low-mass terrestrial planets