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Image Credits: ESA – C. Carreau
May 6-‐8, 2015, Exoplanets in Lund
Exoplanets are extremely diverse in their physical characteris=cs
Hot Jupiter! Super-‐Earth!
Exoplanet Temperatures and Sizes
Images credits: NASA
The Solar System
Ques=on at the new fron=er:
How diverse are the chemical composi=ons and physical processes in exoplanets?
Atmospheric Spectroscopy of Transi=ng Exoplanets
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Deming et al. 2013, Madhusudhan et al. 2014
Knutson et al. 2007
Madhusudhan 2012
Observa=ons • Transmission spectra (IR, visible, UV, X-‐ray) • Secondary eclipse spectra (IR, visible) • Phase curves (IR + visible) • High-‐res (R = 105) spectroscopy (IR)
Inferences • Chemical composi=ons • Temperature profiles
• Clouds and hazes • Upper atmospheres and escape • Atmospheric dynamics
2+ band photometry available for > 30 hot Jupiters
Knutson et al. 2008, Charbonneau et al. 2008, Machalek et al. 2008, O’Donovan et al. 2010, Stevenson et al. 2010, Deming et al. 2013, etc.
1. Recent Advances in Molecular Detec=ons
López-‐Morales et al. (2010)
Campo et al. (2011)
Croll et al. (2011)
Ground-‐based Photometry and Spectroscopy
Model Fit to Photometric Data
Madhusudhan et al. 2011, Nature, 64, 469
Adapted from Madhusudhan et al. 2011, Nature, 469, 64
Data from Lopez-Morales et al. 2010; Croll et al. 2010; Campo et al. 2011
First measurement of atmospheric C/O in a giant planet
Key Molecular Constraints
• H2O/H2 ≤ 6 × 10-‐6
• CH4 /H2 ≥ 8 × 10-‐6
C/O ≥ 1 But cf Crossfield et al. 2012, Cowan et al. 2012, Swain et al. 2012, Stevenson et al. 2014
Anderson et al. 2012; Lendl et al. 2013
Bean et al. 2013
Magellan MMIRS Spectroscopy
Numerous other ground-‐based efforts from Lopez-‐Morales et al. 2010; Croll et al. 2011, 2012; Crossfield et al. 2012,2013; Chen et al. 2014; Wang et al. 2014; Gillon et al. 2012; etc.
Ground-‐based Photometry and Spectroscopy
New Advances with HST WFC3
Swain et al. 2012, Madhusudhan 2012, Stevenson et al. 2014
Deming et al. 2013
Mandell et al. 2014
Deming et al. 2013
Stevenson et al. 2014 Swain et al. 2013
WASP-‐12b
New Advances with HST Transit Spectroscopy (HST WFC3 Large pilot program: 115 HST Orbits, ~10 planets, PI: Drake Deming)
Single Transits/Occulta=ons not adequate for most hot Jupiters!
H2O in Transmission Spectra
Deming et al. 2013, McCullough et al. 2014, Madhusudhan et al. 2014a
H2O in Transmission and Emission
Kriedberg et al. 2014, ApJL Stevenson et al. 2014, Science
WASP-‐43
Phase-‐resolved Spectra of hot Jupiters (HST WFC3 Treasury program: 150 HST Orbits, 4 planets, PI: Jacob Bean)
Stevenson et al. 2014, Science 61 HST Orbits, 6 Transits, 5 Occulta=ons 3 full planetary orbits
Hot Jupiter WASP-‐43b
Phase Resolved Spectroscopy
2. Hazes and Clouds in hot Jupiter Atmospheres
D. K. Sing et al. 2011, MNRAS, 416, 1443 F. Pont et al. 2008, MNRAS, 385, 109
HD 189733b (HST STIS + ACS) Evans et al. 2013
Pont et al. 2008
Sing et al. 2011
Modeling and Theory: Lecavelier Des Etangs et al. 2008, A&A, 481, L83 Helling et al. 2008, A&A, 485, 547
Other results indica=ng high geometric albedos for some hot Jupiters using Kepler: Kepler-‐7b (Demory et al. 2011, ApJ, 735, 12) HAT-‐7b (Chris=ansen et al. 2010, ApJ, 710, 97 )
3. Temperature Profiles in Exoplanetary Atmospheres
Some Context
Earth’s Atmosphere: U. S. Standard Atmosphere
Stratosphere caused by Ozone
Typical model temperature profiles of highly irradiated planets
Do irradiated planets host stratospheres?
Thermal inversions in hot Jupiters (The TiO/VO Hypothesis)
Hubeny, I. et al. 2003, ApJ, 594, 1011 Fortney et al 2006, ApJ, 642, 495
TiO and VO can be very strong absorbers of incident stellar irradiaCon in the visible high in the atmospheres of hot Jupiters, and can hence cause thermal inversions.
Madhusudhan & Seager 2010
Theory of Thermal inversions in hot Jupiters
Planet Gravity (cm s-‐2)
Incide
nt Flux (ergs s-‐1
cm-‐2)
Fortney et al. 2008
Inversion
No Inversion
Other factors influencing thermal inversions
Settling/condensation: Spiegel et al. 2009 Stellar Activity: Knutson et al. 2010 C/O Ratio: Madhusudhan 2012
Knutson et al. 2008, Burrows et al. 2008
HD 209458b
Inferences of Thermal Inversions in Hot Jupiters
Machalek et al. 2008; Fressin et al. 2010; Deming et al. 2010; Anderson et al. 2012; Blecic et al. 2013
Madhusudhan et al. 2011
No Thermal Inversion in HD 209458b
Diamond-‐Lowe et al. 2014
HD 209458b
First Spectroscopic Evidence for a Thermal Inversion
Haynes et al. (in press). On astro-‐ph today!
4. Spectra of Low Mass Planets
Need > 103x low CH4 Need > 103x high CO
GJ 436b Dayside Emission
Knutson et al. 2014
Transmission Spectrum of GJ 436b
Ms = 0.4 M, Rs = 0.5 M, Teff = 3500 K, M3 V
Mp = 22.2 ME, Rp = 4.3 RE, Teq~ 750 K
GJ 436b
Stevenson et al. 2010, Madhusudhan & Seager 2011
Lenoue et al. 2014, in press
Emission Spectrum of GJ 436b
First Detec=on of H2O in an Exo-‐Neptune
Fraine et al. 2014, Nature
Transmission Spectrum of HAT-‐P-‐11b
60 HST orbits Kreidberg et al. 2014
Clouds in the super-‐Earth GJ 1214b (T ≈ 550 K)
Characterizing Super-‐Earth Atmospheres (GJ 1214b)
Mp = 6.55 ± 0.98 ME Rp = 2.678 ± 0.13 RE Teq = 400 -‐ 550 K
Key Merit: Orbits an M Dwarf (M = 0.16 Ms, R = 0.2 Rs)
Houer is beuer!
Currently, houer Super-‐Earths are beuer targets: 1. Larger atmospheric signal 2. Lower probability of clouds or hazes
Madhusudhan & Redfield (2014)
Madhusudhan & Redfield 2015
Simulated Thermal Spectra of 55 Cancri e
Simulated Data
First Detec=on of Variability in a Super-‐Earth
Demory, Gillon, Madhusudhan, & Queloz 2015
Extreme Volcanism on a Super-‐Earth?
Credits: NASA/JPL-‐Caltech/R. Hurt
Direc=ons for the Future
• Characteriza=on of atmospheres and interiors of exoplanets
• Detec=on of small planets orbi=ng nearby stars
The Golden Age of Exoplanet Science
TESS (NASA)
CHEOPS (ESA)
The James Webb Space Telescope
The future from ground E-‐ELT, GMT, TMT
PLATO (ESA)
Major Science Direc=ons
• Composi=ons, thermal profiles, & dynamics
• Characteriza=on of clouds and hazes • Constraints on planet forma=on and migra=on
• Super-‐Earth atmospheres and Interiors
• Bio-‐signatures in habitable planets • Precision atmospheric science of exoplanets
Major Science Direc=ons
• Composi=ons, thermal profiles, & dynamics
• Characteriza=on of clouds and hazes • Constraints on planet forma=on and migra=on
• Super-‐Earth atmospheres and Interiors
• Bio-‐signatures in habitable planets • Precision atmospheric science of exoplanets
Madhusudhan et al. 2014a
New HST Detec=ons of H2O
High-‐precision H2O Measurements
Madhusudhan et al. 2014a
Constraints on Planet Forma=on
Image Credits: NASA
Owen et al 1999; Bolton et al. 2010
Atmospheric abundances in Jupiter
C/O ≥ 1 (Strange Territory)
C/O = 0.5 (Working Hypothesis)
Lodders 2004; Kuchner & Seager 2005; Madhusudhan et al. 2011b, Mousis et al. 2012.
H2O abundance is not known for Jupiter
Hot Jupiter 51 Peg b (Mayor and Queloz 1995)
How did hot Jupiters form and migrate?
H2O
CO2
Two Pathways for Hot Jupiter Migra=on 1. Migra=on through the disk (~Circular + aligned orbits) 2. Migra=on by scauering (High eccentric + misaligned orbits)
Warped disks make the two scenarios degenerate (Batygin et al. 2013)
Effect of Forma=on Condi=ons on C/O ra=os
Mousis et al. 2009, Madhusudhan et al. 2011b
H2O 0.559 0CO 0.253 0.471CO2 0.0966 0.221NH3 0.0349 0.0958H2S 0.0149 0.0369N2 0.0211 0.0579CH3OH 0.0166 0.0378CH4 2.94E-03 0.0789PH3 6.12E-04 1.29E-03
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Madhusudhan, Amin, & Kennedy 2014
Prescrip=ons for Accre=on and Disk Migra=on
General behavior for Accre=on + Type-‐II Migra=on
Ida & Lin 2004
Type-‐II Migra=on
Gas and Solid Accre=on
Alibert et al. 2005
Gap Opening Condi=on
Chemical Signatures of hot Jupiter Migra=on
Madhusudhan, Amin, & Kennedy 2014
Low metallici=es in hot Jupiters likely suggest disk-‐free migra=on
Influence of non-‐solar C/O
Madhusudhan 2012; Also see Moses et al. 2013, Kopparapu et al. 2013
Summary
• Currently hot giant planets provide the best targets for atmospheric spectroscopy of exoplanets.
-‐ Revealing a diversity in chemical abundances -‐ Constraints on temperature profiles, clouds and hazes, dynamics.
• Upcoming facili=es will make such observa=ons possible for a much larger sample of planets (both giant and smaller)
• New science direc=ons include constraints on planet forma=on and super-‐Earth interiors, in addi=on to detailed atmospheric characteriza=on.