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Solar System Planets - Caitlin Griffith

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Brave new worlds
May 29-June 03, 2016 – Lake Como School of Advanced Studies

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Solar System Planets - Caitlin Griffith

  1. 1. Solar System Planets! What can they tell us about exoplanets" Planet & atmosphere composition! Temperature profile! Clouds! ! A tiny tour of atmospheric processes
  2. 2. Solar System Planets! What can they tell us about exoplanets" Life! ! A tiny tour of atmospheric processes
  3. 3. Jovian Planets" What do the Giant Planets tell us about Hot Jupiters? !
  4. 4. Paradigm set by the solar system" They should not exist.
  5. 5. Paradigm set by the solar system" They should not exist.
  6. 6. Exoplanet Masses"
  7. 7. What do Jovian Planet characteristics tell us about Hot Jupiter characteristics?" ! n  Thermal Structure! n  Composition! n  Clouds!
  8. 8. Equilibrium Temperature (Teq*)" * The blackbody temperature that the planet radiates at, assuming that the power absorbed equals the power emitted
  9. 9. Equilibrium Temperature (Teq*)" * The blackbody temperature that the planet radiates at assuming that the power absorbed equals the power emitted
  10. 10. Bond Albedo (A) and Teq" PLANET" Albedo" Semi-major" Axis (AU)" Teq (K)" Teff (K)" Femit/ Fabsorb" JUPITER! 0.343! 5.2! 113! 124! 2.5! SATURN! 0.342! 9.54! 83! 95! 2.3! URANUS! 0.300! 19.18! 60! 60! ~1! NEPTUNE! 0.290! 30.06! 48! 59! 2.7! The bond albedo is the total radiation reflected from an object compared to the total incident radiation from the Sun.
  11. 11. Thermal Profiles" Robinson & Catling 2013
  12. 12. Composition! (bulk)"
  13. 13. Bulk Composition" Terrestrial Planet Giant Planets:
  14. 14. Density of Giant Planets" Planet" Distance from Sun" Mass " kg" Radius " km" Density " g/cm3" Jupiter! 5.2 AU! 1.9x1030 ! 70,850 ! 1.326 ! Saturn! 9.5 AU! 5.68×1026 ! 58,232 ! 0.687! Uranus! 19.2 AU! 8.7×1025 ! 25,362 ! 1.27! Neptune! 30 AU! 1.0×1026 ! 24,622 ! 1.64!
  15. 15. Composition! (Atmospheric)"
  16. 16. ch4" Fink & Larson 1979 Near-IR spectra Jovian Planets & Titan
  17. 17. ch4" Fink & Larson 1979 Near-IR spectra Jovian Planets & Titan
  18. 18. Burrows and Orton 2009 Voyager IRIS data
  19. 19. Where do these molecules come from?" We can only really measure the composition of the upper atmosphere. Are we just measuring the composition of the solar nebula?
  20. 20. Ice lines" Oberg et al. 2011 C/O ratios
  21. 21. Conditions of Jupiter’s accretion" From Owen 1999 See Jupiter book, chapters by Taylor and Lunine
  22. 22. Water" Roos-Serote et al. 2000 Emission spectrum at 5 microns Juno 1.3—50 cm
  23. 23. Molecular Composition"
  24. 24. Composition"
  25. 25. Thermochemical Equilibrium" Chemistry driven by the thermal energy of the system. In equilibrium, the Gibbs free energy, G, is a minimum. Definitions: H= enthalpy, S=Entropy, T=temperature Then: Substituting for dH: Isothermal process in which the pressure is changed alters G by: i.e.
  26. 26. Continued" From above: As ΔG depends on pressure, for all compounds, a standard is adopted. ΔG is defined relative to its pure elements at P = 1 bar (ΔG°)*. Where: * ΔG° is called the Gibbs free energy of formation, available in e.g. JANAF tables on web. Then from top equation: Consider Then: Define: Where: à
  27. 27. An Example! At what T & P is carbon carried by CO vs CH4?" Notation: Where: Assumptions: Equilibrium à
  28. 28. Thermochemical! & photochemistry" Anders and Grevesse 1989 Moses et al. 2011
  29. 29. Back to the Thermal Profiles! But first a little RT"
  30. 30. }  Definition: solid angle Unit: steradian
  31. 31. }  Intensity: }  Mean intensity: What is the Sun’s intensity? What is its flux? What if you wanted to know the flux? That is the total number of photons absorbed per unit surface area per second per unit wavelength?
  32. 32. }  Intensity }  Flux Direction of intensity beam Direction of Flux What is the Sun’s intensity? What is its flux? = cos(θ) θ
  33. 33. }  Extinction: an interaction between light & matter that decreases the intensity }  Emission adds to intensity: }  Equation of Transfer: Can be due to light scattered back into beam!
  34. 34. }  Equation of Transfer: }  Definition of Source Function: }  Optical Depth: }  Simplified Equation: Column Abundance:
  35. 35. }  Equation of Transfer: }  Definition of Source Function: }  Optical Depth: }  Simplified Equation: Column Abundance: or* dτ = κνρ1ρ2ds
  36. 36. }  Equation of Transfer: How would you solve this equation, i.e. get the intensity terms on one side of the equation?
  37. 37. }  Equation of Transfer: }  Multiply both sides by eτ }  General Solution:
  38. 38. 1)  Solution for no source function?
  39. 39. 1)  Solution for no source function?
  40. 40. Essai d’optique sur la gradation de la lumière (1729) Pierre Bouguer 1698-1758Johann Lambert (1728-1777) August Beer 1825-1863
  41. 41. Planck Function
  42. 42. Back to the T-P Profile! (really)"
  43. 43. Thermal Profiles" Robinson & Catling 2013 Opacity governed by dτ = κνρ1ρ2ds Heating by the Sun
  44. 44. Pressure induced absorption on Titan" Optical depth: dτ = κνρ1ρ2ds
  45. 45. Pressure induced absorption on Jupiter" Voyager IRIS data
  46. 46. Earth’s IR opacity" Optical depth of the wings of strong bands depend on density squared.
  47. 47. Earth vs Titan" O3 CO2 CH4 & haze C2H6
  48. 48. Flux = Σ F(λi) = energy that crosses a unit area per unit time Steady state atmosphere: dF/dz = 0 Heat needed per mass to raise temp by 1 degree:: Heat / volume: Heating Rate: Heating rate:
  49. 49. Titan
  50. 50. Tropopause “roughly” at 0.1 bar" Showman 2009
  51. 51. Condensation" CH4 clouds (Neptune) Thermochemical Equilibrium models with condensation Lodders 2004
  52. 52. Cloud compositions" Hotter H2O 273 K NH3 CH4 Earth Jupiter Saturn Uranus Neptune Titan
  53. 53. Jovian Planet Profiles" Or H2S
  54. 54. Cloud origins" Condensation Photolysis & Condensation Photolysis Sometimes aided by ions
  55. 55. 1.6 um / 3 bar 2.2 um / 0.5 bar 2.7 um / 3 bar 3.0 um / 3 bar 5.0 um / ~5 bar Composite MULTIPLE CLOUD DECKS
  56. 56. Jupiter’s Clouds: Models Ackerman&Marley2001 Westetal.2006 Condensate mixing ratio NH3 cloud frain = Vsed/ Vconv ALTITUDES AFFECTED BY DYNAMICS
  57. 57. Jupiter’s Zones & Belts
  58. 58. Jupiter’s Clouds vary spatially" Nominal Galileo Entry Site NH3 ? NH4SH? H2O?
  59. 59. Saturn Scattered sunlight Thermal radiation AFFECT BOTH SCATTERING AND ABSORPTION
  60. 60. Uranus" C2H6 C2H2 Haze 1 mbar CH4 clouds 1.3 bar Higher CH4 clouds P<1bar Base clouds at ~6 bar CLOUDS FROM DIFFERENT PROCESSES
  61. 61. Neptune Optically thick blue cloud deck at ~3.3 bar H2S or NH3 GDS, anticyclone CH4 “orographic” Clouds (1 bar) TEMPORAL CLOUDS
  62. 62. REVIEW" Temperature Composition Clouds Are all interconnected
  63. 63. Structure of Giant Planets! Guidelines" Composition: Main constituents are those expected from thermochemical equilibrium Minor species set by photochemistry of main constituents Temperature: Equilibrium temperature (Teq) established with a ~0.3 bond albedo* T-P profile set roughly by convective-radiative equilibrium But dynamics also plays a role. Also internal heat plays a role Clouds: Cloud composition established mainly by condensation. Clouds vary temporally and spatially, with depth & horizontally. Dynamics is affected by the spin, composition and heating * Risky coincidence?
  64. 64. Structure of Giant Planets" Guidelines: Main constituents are those expected from thermochemical equilibrium Minor species set by photochemistry starting from the main constituents Effective temperature (Teq) established with a ~0.3 bond albedo Cloud composition established mainly by condensation. Difficulties: Cloud thickness and variability (temporal & spatial) difficult to establish àRepeated transit observations at different wavelengths Abundances difficult to establish if clouds are present àMeasure exoplanets with different temperatures àMeasure exoplanets with different “metallicities” T-P profile established by Teq, composition, internal heat & clouds àMeasure the entire emission spectrum of exoplanet to get Teff Seems almost manageable

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