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Exoplanet Characterization with JWST
Jeff Valenti(Space Telescope Science Institute)
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Exoplanet Characterization with JWST
Investigators: Exoplanet community
Scientific Category: Exoplanets
Scientific Keywords:Planet formation and evolution
Planetary atmospheres
Instruments: NIRSpec, MIRI, NIRCam
Proprietary Period: 0-12 months
Requested Allocation: 2600 hours (6% of 5 years)
DRAFT – please circulate!
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Key Questions
Explore the diversity of planetsDensity, Composition, Stratospheres, Eccentricity, …
How do planets form/arrive so close to star?Signatures of core-accretion processes
Migration and other dynamical processes
Processes that control planetary atmospheresCloud formation, non-equilibrium chemistry, etc.
Stellar irradiation
Origin of water
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Core-Accretion Scenario
Phase ICore formation
via rapid accretionof planetesimalsin “feeding zone”
Phase IIEnvelope formation viagradual gas accretion
Phase IIIGiant planet formationvia rapid gas accretion
IsolationMass
Core + Envelope
Core Only
Pollack et al. (1996, Icarus, 124, 62)
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Diverse Formation and Evolution
LowDensity
HighDensity
ExoplanetDiversity
Core mass, composition,migration, heating, …
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Schematic of Transit and Eclipse Science
Measure size of planet 10-2
See starlight transmittedthrough planet atmosphere 10-4
EclipsePlanet thermalemission appearsand disappears 10-3
Learn about atmosphericcirculation from thermalphase curves
Transit
Seager & Deming (2010, ARAA, 48, 631)
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Program Goals
Refine planet radius and hence planet densityAtmospheric composition: H, CH4, CO, CO2, H2O, …Vertical temperature structure, effect of irradiationLongitudinal temperature structure, heat distributionLatitudinal temperature structure (grazing eclipses)Measure small eccentricities transit/eclipse timingDependence on planet mass (Jupiter super-Earth)Constrain formation, evolution, and structure modelsSample stellar surface features (limb, spots, …)Verify transits of terrestrial planets (e.g. Kepler)Assess habitability?Planetary exospheres?
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Eclipse Spectroscopy and Photometry
2 3 4 2010
Model
IRS
NICMOS
MIPS
IRS
HD 189733b
Swain et al., Astro2010 white paper 8
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GJ 1214b Transit Spectrum from the Ground
Bean et al. (2010, Nature, 468, 669)R=45
VLT/FORS2
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HD 189733b Thermal Emission from the Ground
NLTECH4
?
Swain et al. (2010, Nature, 463, 637)10
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JWST Instrument Configurations
7
42
6421033
transits eclipses
imaging
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Spectrum of a Planet Host
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Timeline of a Transit Observation
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Thermal Emission from a Hot Jupiter
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Simulated MIRI Observations of HD 189733b
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GJ 1214
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Transit Spectrum of Habitable “Ocean Planet”
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Thermal Emission versus Orbital Phase
0.97
9 tra
nsit
dept
hPeak temperatureprecedes eclipse
by 16±6˚
HD 189733 b
Spitzer, 8 µm, 33 hours
970 K
1210 K
Knutson et al. (2007, Nature, 447, 183)
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Photometric Precision as Target Drifts
SinglePixel
Sum of 5x1 pixels
Barron et al. (2007, PASP, 119, 466)
Charge DiffusionH2RG @ 1.05 µmNot JWST detector
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50 Good Targets Today… Want 50 Best for JWST
KeplerCoRot HAT, WASP, XO, …
HD 189733
RV ElektraTESS
GJ 1214
HD149026
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Transit Study of Cool Atmospheres
NIRCamTransit
S/N
Transit Depth
(%)
PlanetRadius
(RJ)
OrbitPeriod
(d)
Orbita
(AU)
Star Mag (R)
Star Rad(Rsun)
Star Teff
(K)
PlanetTeq
(K)73.7 0. 74 1.13 17.86 0.141 11.35 1.32 6419 86862.4 0. 64 0.75 125.6 0.499 12.39 0.94 5638 34446.5 0. 47 1.13 22.3 0.165 12.20 1.66 6090 85139.7 0. 40 0.91 75.1 0.4 11.71 1.44 6987 58630.7 0. 31 0.59 9.43 0.089 11.58 1.065 5533 84414.0 0. 14 0.62 90.5 0.42 12.20 1.66 6090 534
Good targets from Kepler… better ones coming!
Extracted from Bill Borucki’s presentation on Monday. Data from Tome Greene.
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Strawman Survey Program
Goal Targets Visits HoursAssess strategies 1+ 20 100
Jupiter Eclipse Survey 50 2 500
Jupiter Transit Survey 10 10 500
Cool Atmospheres 10 2 100
Neptune Atmospheres 10 20 1000
Super-Earth Atmospheres 2 40 400
Phase curves, Weather, … … … …Assumes an average of 5 hours / visit