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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)

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?

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

HD 189733b Thermal Emission from the Ground

NLTECH4

?

Swain et al. (2010, Nature, 463, 637)10

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JWST Instrument Configurations

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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”

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