Exo-Cartography (Mapping the Climate and Oceans of Exoplanets) Nick Cowan CIERA Postdoctoral Fellow Northwestern University May 17, 2011
What I Won t Talk About Pallé et al. (2009) May 17, 2011 Nick Cowan's Talk for Earth 351 2
PART 1 The Present of Exoplanet Characterization
Hot Jupiters May 17, 2011 Nick Cowan's Talk for Earth 351 4
Hot Jupiter upiter Close to Star: a 10-2 a J High Irradiation: F 10 4 F J Hot: T 10 T J Strong Tides: F tidal 10 6 F tidal, J May 17, 2011 Nick Cowan's Talk for Earth 351 5
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) May 17, 2011 Nick Cowan's Talk for Earth 351 6
Outline 1. Thermal Phase Variations 2. Low Signal/Noise Lightcurves 3. High Signal/Noise Lightcurves May 17, 2011 Nick Cowan's Talk for Earth 351 7
Outline 1. Thermal Phase Variations 2. Low Signal/Noise Lightcurves 3. High Signal/Noise Lightcurves May 17, 2011 Nick Cowan's Talk for Earth 351 8
Observing Hot Jupiters Sweet Spot (Mid-IR) Spitzer May 17, 2011 Nick Cowan's Talk for Earth 351 9
Transit May 17, 2011 Nick Cowan's Talk for Earth 351 10
Infrared Light Curve Brightness 100% 99% Transit Transit Depth = (R p /R * ) 2 Time May 17, 2011 Nick Cowan's Talk for Earth 351 11
Eclipse May 17, 2011 Nick Cowan's Talk for Earth 351 12
Infrared Light Curve Brightness 100.3% 100% 99% Transit Star + Planet Star Eclipse Eclipse Depth (R p /R * ) 2 (T day /T * ) Time May 17, 2011 Nick Cowan's Talk for Earth 351 13
Thermal Phases May 17, 2011 Nick Cowan's Talk for Earth 351 14
Thermal Phase Variations Brightness Star + Planet Star Thermal Phase Amplitude (R p /R * ) 2 (T day - T night )/T * 100.3% 100.1% 100% Transit Eclipse Time May 17, 2011 Nick Cowan's Talk for Earth 351 15
Outline 1. Thermal Phase Variations 2. Low Signal/Noise Lightcurves 3. High Signal/Noise Lightcurves May 17, 2011 Nick Cowan's Talk for Earth 351 16
Low S/N Phase Functions HD 179949 @ 8 micron (Cowan, Agol & Charbonneau 2007) 51 Peg @ 8 micron (Cowan, Agol & Charbonneau 2007) HD 209458 @ 8 micron (Cowan, Agol & Charbonneau 2007) Ups Androm. @ 24 micron (Crossfield et al. 2010) May 17, 2011 Nick Cowan's Talk for Earth 351 17
What Determines Tday and Tnight? 1. Bright Star: T0 = Teff (R*/a)1/2 Doesn t affect relative brightness 2. Bond Albedo: A Keeps planet cool Less infrared light 3. Recirculation: ε τrad /τadv Cools day-side Warms night-side May 17, 2011 Nick Cowan's Talk for Earth 351 18
Where 24 Transiting Planets Live (a Probability Distribution Function) Day-Side Temperature Degeneracy High Albedos Not Common A B < 0.35 Without Optical Data! Cowan & Agol 2011b May 17, 2011 Nick Cowan's Talk for Earth 351 19
Outline 1. Thermal Phase Variations 2. Low Signal/Noise Lightcurves 3. High Signal/Noise Lightcurves May 17, 2011 Nick Cowan's Talk for Earth 351 20
High S/N Phase Functions (Knutson et al. 2007, 2009a) 33 hour observation Rotation HD 189733 (8 micron) Eclipse Transit Phase Function Cowan & Agol (2008) May 17, 2011 Nick Cowan's Talk for Earth 351 21
Map Coordinates May 17, 2011 Nick Cowan's Talk for Earth 351 22
Planet Mapping Basics 2D Brightness Map Hydrodynamic Simulation (Cho et al. 2003) Integral LONGITUDINAL MAP Convolution LIGHT CURVE Can de-convolve lightcurve IF STEADY-STATE CLIMATE (Cowan & Agol 2008) May 17, 2011 Nick Cowan's Talk for Earth 351 23
Eclipse Variability & Mapping Stack seven Spitzer 8 micron eclipses of HD 189733b: F day changed by < 2.7% on timescales of days to years Agol, Cowan et al. (2010) ~40 sec discrepancy in time of eclipse constrains hot spot location May 17, 2011 Nick Cowan's Talk for Earth 351 24
Eclipse + Phase Mapping Majeau, Agol & Cowan (in prep) May 17, 2011 Nick Cowan's Talk for Earth 351 25
Summary T 0 A B T day T night ε Thermal Eclipse Depth T day Thermal Phase Amplitude T night T day and T night A B and ε Shape of Thermal Phase/Eclipse T(Φ,t) T(Φ,t) τ rad and τ adv May 17, 2011 Nick Cowan's Talk for Earth 351 26
Part 2 The Future of Exoplanet Characterization
The Habitable Zone May 17, 2011 Nick Cowan's Talk for Earth 351 28
Image of a Nearby Planetary System A. Time-Averaged Spectroscopy B.Time-Resolved Photometry High-Contrast Optical Imaging Space-Based Telescope (>5m) Internal/External Coronograph N+1 decades from now Habitable Zone Planet Host Star Blocked/Nulled (Simulated image from Oakley & Cash 2009) May 17, 2011 Nick Cowan's Talk for Earth 351 29
Possible HZ Worlds Equatorial Earth (EPOXI) Snowball Earth (Model) A Priori Unknown Climate State A Priori Unknown Obliquity Polar Earth (EPOXI) May 17, 2011 Nick Cowan's Talk for Earth 351 30
Outline Thermal Phase Variations Colors of Exoplanets Snowball Earth Model Exo-Cartography May 17, 2011 Nick Cowan's Talk for Earth 351 31
Eccentricity Seasons (Any Viewing Geometry) Apastron Diurnal Cycle (Edge-On Orbits Best) Day-Side (Superior Conjunction) Night-Side (Inferior Conjunction) Periastron Cowan & Agol (2011a) Gaidos & Williams (2004) Obliquity Seasons (Pole-On Rotation Best) Winter Solstice Summer Solstice May 17, 2011 Nick Cowan's Talk for Earth 351 32
1) Eccentricity and Obliquity Affect Climate 2) Climate Affects Response to Eccentricity, Obliquity and Diurnal Forcing Use State-of-the-Art GCMs to compare thermal phase variations from: - Temperate Planet (Large Thermal Inertia) - Snowball Planet (Small Thermal Inertia) Work in Progress with Dorian Abbot & Aiko Voigt May 17, 2011 Nick Cowan's Talk for Earth 351 33