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The search for habitable planets and the quest to understand their origins D.N.C. Lin KIAA, Peking University, University of California, Santa Cruz, Kavli.

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Presentation on theme: "The search for habitable planets and the quest to understand their origins D.N.C. Lin KIAA, Peking University, University of California, Santa Cruz, Kavli."— Presentation transcript:

1 The search for habitable planets and the 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

2 High-precision spectroscopy 2/30

3 Mass-period distribution A continuous logarithmic period distribution A pile-up near 3 days and another pile up near 2-3 years Does 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

4 Avenues of planet formation 4/30

5 Hillenbrand & Meyer 2000 Inner disks disappear ~ 10 Myr  Per PleiadesHyades Ursa Major TW Hyd N2264 IC 348 L1641b Lupus Cha ONC N7128 LH  101 Taurus L1641y Mon R2 N1333 CrA Trap N2024  Oph 0.1 1 101001 Gyr Age (Myr) 0.0 0.2 0.4 0.6 0.8 1.0 Fraction of disks 5/30Gas accretion rate

6 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 7/30

8 Feeding zones:  10 r Hill Isolation mass: M isolation ~    a 3 From planetesimals to embryos Initial growth: (runaway) 8/30

9 type-II migration planet’s perturbation viscous diffusion type-I migration disk torque imbalance Disk-planet tidal interactions viscous disk accretion Goldreich & Tremaine (1979), Ward (1986, 1997), Tanaka et al. (2002) Lin & Papaloizou (1985),.... 9/30

10 (Mass) growth vs (orbital) decay Loss due to Type I migration Jovian-mass ESP’s are rare around late-type stars Embryos’ migration time scale Outer embryos are better preserved only after significant gas depletion Critical-mass core:M p =5M earth 10/30

11 Dependence on M * 1)  J increases with M * 2) M p and a p increase with M * Do eccentricity and multiplicity depend on M * ? 11/30

12 Planetary interior: diverse structure & Fe/H HD149026b: 67 earth-mass core 12/30

13 Giant impacts 1)Diversity in core mass 2)Spin orientation 3)Survival of satellites 4)Retention of atmosphere 13/30 Late bombardment of planetesimals

14 The period distribution: Type II migration Disk depletion versus migration 14/30

15 Stellar metallicity, mass loss, & circularization of hot Jupiters 1)Early formation 2)Extensive migration 3)High mortality rate 4)Planetary mass loss 5)Tidal circularization 6)Signs of evolution? 15/30

16 short-period cutoff Stopping mechanisms: 1) magnetospheric cavity 2) stellar tidal barrier 3) protoplanetary consumption 4) planetary tidal disruption Prediction: 90% disruption of hot Jupiters Bimodal Q*: prevalence of 1-day planets Ogilvie Tidal inflation Bodenheimer 16/30

17 Transits: atmosphere & structure 29/48 17/30

18 period cutoffs depletion vs growth time Ice giants: Collisions vs ejections Prediction: period fall-off Test: gravitational lense 18/30

19 Multiple systems Diversity in mass distribution Resonant system with limited mass What fraction of Jovian mass planets reside in multiple systems? Is multiplicity more correlated with [Fe/H] or M* than single planets? 19/30

20 Multiple planets a) Induced formation of multiple giants b) Resonant planets c) Formation time scale comparable to migration Bryden 20/30

21 Post Depletion Dynamical Stability Dynamical filling factor: e excitation & chaos 21/30 Rayleigh distribution

22 Migration-free sweeping secular resonances Resonant secular perturbation M disk ~M p (Ward, Ida, Nagasawa) Ups And Transitional disks 22/30

23 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

24 Mean motion resonance capture Tidal decay out of mean motion resonance (Novak & Lai) Impact enlargement Rejuvenation of gas Giant. HD 209458b (Guillot) Detection probability of hot Earth Narayan, Cumming Migration of gas giants can lead To the formation of hot earth Implication for COROT Zhou 24/30

25 Dynamical shake up (Nagasawa, Thommes) Bode’s law: dynamically porous terrestrial planets orbits with low eccentricities with wide separation 25/30

26 Migration, Collisions, & damping 1.Clearing of the asteroid belt 2.Earlier formation of Mars 3.Sun ward planetesimals A.Late formation (10-50 Myr) B.Giant-embryo impacts C.Low eccentricities, stable orbits 26/30

27 Giant impact & lunar formation 1)Lunar material similar to the Earth’s crust. 2)Formation after the differentiation (30 Myr) 3)Mars-size impactor 4)Post impact circular orbit Formation after 60 Myr Formation on 30-60 Myr 27/30

28 Last melting events of chondrules Flash heating: Large  : evaporation Medium  : melting Small  : preservation 28/30

29 Frequency of Earth 29/30

30 Sequential accretion scenario summary 1)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



33 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

34 Disk evolution 6/43 Protostellar disks: Gas/dust = 100 Dabris disks: Gas/dust = 0.01 only external disk but accreting star Transitional disks

35 From dust to planetesimals Retention of heavy elements:  growth ~  dust but  decay ~  gas 6a/43

36 Potential observational signatures Coexistence of gas and solid phase volatile ices Evolution of snow line 8/43

37 Condensation sequence Meteorites: Dry, chondrules & CAI’s Icy moons 9/43

38 Signs of Crystalline grains Bouwman Apai 8a/43

39 Growth during gas depletion Rapid damping: many small residual embryos. Slow damping: large eccentricity Delicate balance: Kominami & Ida Separation of eccentricity Excitation and damping is Needed! 12/43

40 Competition: M growth & a decay Hyper-solar nebula x30 Metal enhancement does not always help! need to slow down migration 10 Myr 1 Myr 0.1 Myr Limiting isolation mass 13a/43

41 Embryos’ type I migration (10 Mearth) Cooler and invisic disks Warmer disks 14/43

42 Accretion onto cores Challenges: 1)Core growth: perturbation slow down & planetesimal gaps (Ida) 2)Radiation transfer efficiency grain survival & opacity (Podolak) 3) Low global  dust (Bryden) Pollack et al Bodenheimer Korycansky 18/43

43 Flow into the Roche lobe Bondi radius (R b =GM p /c s 2 ) Hill’s radius (R h =(M p /3M * ) 1/3 a) Disk thickness (H=c s a/V k ) R b / R h =3 1/3 (M p /M * ) 2/3 (a/H) 2 decreases with M * 21/43 H/a=0.07 H/a=0.04

44 Preferred cradles of gas giants: snow line Limited by: Isolation slow growth 17/43

45 Effect of type I & II migration 22/43 Habitable planets M/s accuracy

46 The mass distribution Origin of desert: Runaway gas accretion Bryden 28/43

47 Metallicity dependence [Fe/H] Two determining factors for the slope: 1)Heavy element retention efficiency, growth vs accretion 2)Growth rate and isolation mass of embryos 29/43

48 Stellar mass-metallicity 30/43 More data needed for high and low-mass stars

49 Sweeping clear of planetesimals Sweeping secular resonance & gas drag  Pic:Duncan, Nagasawa 37a/43

50 Formation of warm Neptunes Jupiter-Saturn secular interaction & multiple extrasolar systems Relativistic detuning in  Arae 39/43

51 A 2 M earth “hot rock” planet in a 7-d orbit observed for 6 months with APF @ 1.3 m/s precision Easily detected! But this short-period planet is much too hot for habitability 40a/43

52 1 M earth 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! 42/43

53 Outstanding issues: 1)Frequency of planets for different stellar masses 2)Completeness of the mass-period distribution 3)Signs of dynamical evolution 4)Mass distribution of close-in planets: efficiency of migration 5)Halting mechanisms for close-in planets 6)Origin of planetary eccentricity 7)Formation and dynamical interaction of multiple planetary systems 8)Internal and atmospheric structure and dynamics of gas giants 9)Satellite formation 10)Low-mass terrestrial planets

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