potential for characterization of transiting planets with jwst
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Potential for Characterization of Transiting Planets with JWST. Nick Cowan (Northwestern). Study Analysis Group 10 (SAG-X). What is the full diversity of planet properties needed to characterize and understand the climate of short-period exoplanets? - PowerPoint PPT PresentationTRANSCRIPT
Potential for Characterization of Transiting Planets with JWST
Nick Cowan (Northwestern)
Study Analysis Group 10 (SAG-X)1. What is the full diversity of planet properties needed to
characterize and understand the climate of short-period exoplanets?
2. Which measurement suites and how much observing time are needed to characterize the climate of transiting planets?
3. Will JWST be able to characterize the atmospheres of transiting terrestrial planets?
4. Which critical measurements will be too expensive or inaccessible to JWST, and can these be obtained with planned observatories?
SAG-X Participants (so far)Daniel Angerhausen (RPI), Natasha Batalha (Penn State), Adrian Belu (Bordeaux), Knicole Colon (Lehigh), Bill Danchi (Goddard), Pieter Deroo (JPL), Jonathan Fortney (UCSC), Scott Gaudi (Ohio State), Tom Greene (Ames), Matt Greenhouse (Goddard), Joe Harrington (UCF), Lisa Kaltenegger (MPIA), Nikole Lewis (MIT), Chuck Lillie (Lillie Consulting), Mercedes Lopez-Morales (CfA), Avi Mandell (Goddard), Emily Rauscher (Princeton), Aki Roberge (Goddard), Franck Selsis (Bordeaux), Kevin Stevenson (Chicago), Mark Swain (JPL)
1D Climate CartoonHe
ight
Temperature Tsurf
Tropopause
Tstrat
ΓTroposphere
Stratosphere
Thermal Emission Probes Near Tropopause
Reflected Light Probes Near Surface
1D Climate Cartoon
Temperature
Heig
ht
Increase Insolationand/or Decrease Albedo
1D Climate Cartoon
Temperature
Heig
ht
Increase Longwave Opacity
1D Climate Cartoon
Temperature
Heig
ht
Decrease SpecificHeat Capacity
Advection
2D Climate Cartoon(eg: height + latitude)
Temperature
Heig
ht
EquatorPole
To learn from exoplanets, we need to measure:• Planetary Albedo• Albedo Gradients• Emitting Temperature• Temperature Gradients (vertical and horizontal)
Unfortunately we don’t have robust predictive models for:• Clouds• Atmospheric Loss• Photochemistry• Geochemical Cycling • Wind Velocities
Predicting vs Measuring Planetary Climate
Model Inputs• Insolation• Eccentricity• Obliquity• Surface Albedo• Greenhouse Gases• Specific Heat Capacity• Surface Gravity• Surface Pressure• Thermal Inertia
Model Outputs• Emitting Temperature• Temperature Gradients• Diurnal Response• Seasonal Response• Cloudiness• Surface Temperature• Precipitation
TransitPhase Variations
Archetypal Short-Period Planets
Hot Earth (CoRoT-7b, Kepler 10b, α Cen Bb)
Temperate Super-Earth (HD 85512 b, GJ 163 c)
Warm Neptune (GJ 1214b, GJ 436b)
Hot Jupiter (HD 209458b, HD 189733b, WASP-12b)
Transit
Thermal Light CurveBrightness
Time
100%
99%Transit
Transit Depth = (Rp/R*)2
Some Transit Depths
Hot Jupiter: 8.8E-3
Hot Earth: 7.3E-5
Temperate Super-Earth: 7.3E-3
Warm Neptune: 2.7E-2
Thermal Light CurveBrightness
Time
100%
99%Transit
Transit depth is different at different wavelengths
Annulus/Stellar Area = 2RpH/R*2
(where scale height H = kBT/μg)
Some Transit Spectral Features
Hot Jupiter: 1.2E-4
Hot Earth: 2.0E-6
Temperate Super-Earth: 6.5E-6
Warm Neptune: 2.4E-4
Eclipse
Thermal Light CurveBrightness
Time
100.3%
99%Transit
Eclipse100%
Eclipse Depth ≈ (Rp/R*)2 (Tday/T*)
Star + PlanetStar
Some Eclipse Depths
Hot Jupiter: 4.0E-3
Hot Earth: 3.3E-5
Temperate Super-Earth: 7.0E-4
Warm Neptune: 8.1E-3
Thermal Light CurveBrightness
Time
100.3%
99%
Transit100%
Star + PlanetStar
Eclipse depth is different at different wavelengths
Eclipse Spectrum ≈ (Rp/R*)2 (Tsurf - Ttrop)/T*
Thermal Phases
Thermal Light Curve
Brightness
Time
100%
TransitEclipse
100.3%
Star + PlanetStar
100.1%
Phase Amplitude ≈ (Rp/R*)2 (Tday - Tnight)/T*
Eclipse Spectroscopy vs. Phase Variations
• Differences in temperature – Vertical (33-200 K)– Zonal (60-2000 K)
• Spectroscopy has to achieve S/N with relatively narrow bandwidth (R>10)
• Phase variations require long-term stability
Predicting vs Measuring Planetary Climate
Model Inputs• Insolation• Eccentricity• Obliquity• Surface Albedo• Greenhouse Gases• Specific Heat Capacity• Surface Gravity• Surface Pressure• Thermal Inertia
Model Outputs• Emitting Temperature• Temperature Gradients• Diurnal Response• Seasonal Response• Cloudiness• Surface Temperature• Precipitation