exo-cartography - northwestern...
TRANSCRIPT
Exo-Cartography(Mapping the Climate and Oceans of Exoplanets)
Nick CowanCIERA Postdoctoral Fellow
Northwestern UniversityMay 17, 2011
May 17, 2011 Nick Cowan's Talk for Earth 351 2
What I Won’t Talk About
Pallé
et a
l. (2
009)
PART 1
The Present of ExoplanetCharacterization
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Hot Jupiters
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Hot Jupiter ≠Jupiter
• Close to Star:a ≈ 10-2 aJ
• High Irradiation:F ≈ 104 FJ
• Hot:T ≈ 10 TJ
• Strong Tides:Ftidal ≈ 106 Ftidal, J
May 17, 2011 Nick Cowan's Talk for Earth 351 6
Hot Jupiter Expectations
1. High Temperatures– No Clouds– Low Albedo
2. Large Power Budget– Day-Night forcing– Rapid Winds
3. Tidally Locked– Weak Coriolis Force– Large Storms
Showman et al. (2009)
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Outline
1. Thermal Phase Variations2. Low Signal/Noise Lightcurves3. High Signal/Noise Lightcurves
1. Thermal Phase Variations2. Low Signal/Noise Lightcurves3. High Signal/Noise Lightcurves
May 17, 2011 Nick Cowan's Talk for Earth 351 8
Outline
1. Thermal Phase Variations2. Low Signal/Noise Lightcurves3. High Signal/Noise Lightcurves
1. Thermal Phase Variations2. Low Signal/Noise Lightcurves3. High Signal/Noise Lightcurves
May 17, 2011 Nick Cowan's Talk for Earth 351 9
Observing Hot Jupiters
Sweet Spot(Mid-IR)
Spitzer
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Transit
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Infrared Light Curve
Brightness
Time
100%
99%Transit
Transit Depth = (Rp/R*)2
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Eclipse
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Infrared Light Curve
Brightness
Time
100.3%
99%Transit
Eclipse100%
Eclipse Depth ≈ (Rp/R*)2 (Tday/T*)
Star + PlanetStar
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Thermal Phases
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Thermal Phase Variations
Brightness
Time
100%
TransitEclipse
100.3%
Star + PlanetStar
100.1%
Thermal Phase Amplitude ≈ (Rp/R*)2 (Tday - Tnight)/T*
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Outline
1. Thermal Phase Variations2. Low Signal/Noise Lightcurves3. High Signal/Noise Lightcurves
1. Thermal Phase Variations2. Low Signal/Noise Lightcurves3. High Signal/Noise Lightcurves
May 17, 2011 Nick Cowan's Talk for Earth 351 17
Low S/N Phase Functions
Ups Androm. @ 24 micron(Crossfield et al. 2010)
51 Peg @ 8 micron(Cowan, Agol & Charbonneau 2007)
HD 179949 @ 8 micron(Cowan, Agol & Charbonneau 2007)
HD 209458 @ 8 micron(Cowan, Agol & Charbonneau 2007)
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What Determines Tday and Tnight ?
1. Bright Star: T0 = Teff (R*/a)1/2
• Doesn’t affect relativebrightness
2. Bond Albedo: A• Keeps planet cool• Less infrared light
3. Recirculation: ε ≈ τrad /τadv
• Cools day-side• Warms night-side
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Where 24 Transiting Planets Live(a Probability Distribution Function)
High AlbedosNot CommonAB < 0.35
Day-Side TemperatureDegeneracy
Cow
an &
Ago
l 201
1b
Without Optical Data!
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Outline
1. Thermal Phase Variations2. Low Signal/Noise Lightcurves3. High Signal/Noise Lightcurves
1. Thermal Phase Variations2. Low Signal/Noise Lightcurves3. High Signal/Noise Lightcurves
May 17, 2011 Nick Cowan's Talk for Earth 351 21
High S/N Phase Functions (Knutson et al. 2007, 2009a)
HD 189733(8 micron)
Transit
Eclipse
Phase Function
33 hour observationRotation
Cowan & Agol (2008)
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Map Coordinates
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Planet Mapping Basics
LONGITUDINAL MAPLIGHT CURVE
Hydrodynamic Simulation(Cho et al. 2003)
Can de-convolve lightcurveIF STEADY-STATE CLIMATE(Cowan & Agol 2008)
Convolution
Integral2D Brightness Map
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Eclipse Variability & Mapping
Ago
l, C
owan
et a
l. (2
010)
Stack seven Spitzer 8 micron eclipses of HD 189733b:
~40 sec discrepancy in time of eclipse constrains hot spot location
Fday changed by < 2.7%
…on timescales ofdays to years
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Eclipse + Phase Mapping
Maj
eau,
Ago
l & C
owan
(in
prep
)
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Summary
• Thermal Eclipse Depth → Tday• Thermal Phase Amplitude → Tnight• Tday and Tnight → AB and ε• Shape of Thermal Phase/Eclipse → T(Φ,t)• T(Φ,t) → τrad and τadv
T0 AB Tday
Tnight
ε
Part 2
The Future of ExoplanetCharacterization
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The Habitable Zone
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Image of a Nearby Planetary System
(Simulated image from Oakley & Cash 2009)
A. Time-Averaged SpectroscopyB.Time-Resolved Photometry
Habitable Zone Planet
• High-Contrast Optical Imaging• Space-Based Telescope (>5m)• Internal/External Coronograph• N+1 decades from now…
Host StarBlocked/Nulled
May 17, 2011 Nick Cowan's Talk for Earth 351 30
Possible HZ Worlds
A PrioriUnknownObliquity
SnowballEarth(Model)
Polar Earth(EPOXI)
EquatorialEarth(EPOXI)
A PrioriUnknown Climate State
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Outline
• Thermal Phase Variations• Colors of Exoplanets• Snowball Earth Model• Exo-Cartography
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Day-Side(Superior Conjunction)
Night-Side(Inferior Conjunction)
Periastron
Apastron
Winter Solstice
Summer Solstice
Diurnal Cycle(Edge-On Orbits Best)
Eccentricity Seasons(Any Viewing Geometry)
Obliquity Seasons(Pole-On Rotation Best)
Gaidos & Williams (2004)Cowan & Agol (2011a)
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1) Eccentricity and Obliquity Affect Climate2) Climate Affects Response to Eccentricity, Obliquity and Diurnal Forcing
Use State-of-the-Art GCMs to comparethermal phase variations from:- Temperate Planet (Large Thermal Inertia)- Snowball Planet (Small Thermal Inertia)
Work in Progress with Dorian Abbot & Aiko Voigt