Poten&al  for  Characteriza&on  of  Transi&ng  Planets  with  JWST  

Nick  Cowan    (Northwestern)  

Study  Analysis  Group  10  (SAG-‐X)  1.  What  is  the  full  diversity  of  planet  proper&es  needed  

to  characterize  and  understand  the  climate  of  short-‐period  exoplanets?    

2.  Which  measurement  suites  and  how  much  observing  &me  are  needed  to  characterize  the  climate  of  transi&ng  planets?    

3.   Will  JWST  be  able  to  characterize  the  atmospheres  of  transi8ng  terrestrial  planets?    

4.   Which  cri8cal  measurements  will  be  too  expensive  or  inaccessible  to  JWST,  and  can  these  be  obtained  with  planned  observatories?      

SAG-‐X  Par&cipants  (so  far)  Daniel  Angerhausen  (RPI),  Natasha  Batalha  (Penn  State),  Adrian  Belu  (Bordeaux),  Knicole  Colon  (Lehigh),  Bill  Danchi  (Goddard),  Pieter  Deroo  (JPL),  Jonathan  Fortney  (UCSC),  ScoV  Gaudi  (Ohio  State),  Tom  Greene  (Ames),  MaV  Greenhouse  (Goddard),  Joe  Harrington  (UCF),  Lisa  Kaltenegger  (MPIA),  Nikole  Lewis  (MIT),  Chuck  Lillie  (Lillie  Consul&ng),  Mercedes  Lopez-‐Morales  (CfA),  Avi  Mandell  (Goddard),  Emily  Rauscher  (Princeton),  Aki  Roberge  (Goddard),  Franck  Selsis  (Bordeaux),  Kevin  Stevenson  (Chicago),  Mark  Swain  (JPL)    

1D  Climate  Cartoon  He

ight  

Temperature   Tsurf  

Tropopause  

Tstrat  

Γ  Troposphere  

Stratosphere  

Thermal  Emission  Probes  Near  Tropopause  

Reflected  Light  Probes  Near  Surface    

1D  Climate  Cartoon  

Temperature  

Height  

Increase  Insola&on  and/or  Decrease  Albedo  

1D  Climate  Cartoon  

Temperature  

Height  

Increase    Longwave    Opacity  

1D  Climate  Cartoon  

Temperature  

Height  

Decrease  Specific  Heat  Capacity  

Advec&on  

2D  Climate  Cartoon  (eg:  height  +  la&tude)  

Temperature  

Height  

To  learn  from  exoplanets,    we  need  to  measure:  •   Planetary  Albedo  •   Albedo  Gradients  •   Emiang  Temperature  •   Temperature  Gradients        (ver&cal  and  horizontal)  

Unfortunately  we  don’t  have  robust  predic&ve  models  for:  •   Clouds  •   Atmospheric  Loss  •   Photochemistry  •   Geochemical  Cycling    •   Wind  Veloci&es  

Predic&ng  vs  Measuring    Planetary  Climate  

Model  Inputs  •  Insola&on  •  Eccentricity  •  Obliquity  •  Surface  Albedo  •  Greenhouse  Gases  •  Specific  Heat  Capacity  •  Surface  Gravity  •  Surface  Pressure  •  Thermal  Iner&a  

Model  Outputs  •  Emiang  Temperature  •  Temperature  Gradients  •  Diurnal  Response  •  Seasonal  Response  •  Cloudiness  •  Surface  Temperature  •  Precipita&on  

Transit  Phase  Varia&ons  

Archetypal  Short-‐Period  Planets    

Hot  Earth  (CoRoT-‐7b,  Kepler  10b,  α  Cen  Bb)      Temperate  Super-‐Earth  (HD  85512  b,  GJ  163  c)      Warm  Neptune  (GJ  1214b,  GJ  436b)      Hot  Jupiter  (HD  209458b,  HD  189733b,  WASP-‐12b)  

Transit  

Thermal  Light  Curve  Brightness  

Time  

100%  

99%  Transit  

Transit  Depth  =  (Rp/R*)2  

Some  Transit  Depths  

Hot  Jupiter:  8.8E-‐3  

Hot  Earth:  7.3E-‐5  

Temperate  Super-‐Earth:  7.3E-‐3  

Warm  Neptune:  2.7E-‐2  

Thermal  Light  Curve  Brightness  

Time  

100%  

99%  Transit  

Transit  depth  is  different    at  different  wavelengths  

Annulus/Stellar  Area  =  2RpH/R*2  (where  scale  height  H  =  kBT/μg)  

Some  Transit  Spectral  Features  

Hot  Jupiter:  1.2E-‐4  

Hot  Earth:  2.0E-‐6  

Temperate  Super-‐Earth:  6.5E-‐6  

Warm  Neptune:  2.4E-‐4  

Eclipse  

Thermal  Light  Curve  

Brightness  

Time  

100.3%  

99%  Transit  

Eclipse  100%  

Eclipse  Depth  ≈  (Rp/R*)2  (Tday/T*)  

Star  +  Planet  Star  

Some  Eclipse  Depths  

Hot  Jupiter:  4.0E-‐3  

Hot  Earth:  3.3E-‐5  

Temperate  Super-‐Earth:  7.0E-‐4  

Warm  Neptune:  8.1E-‐3  

Thermal  Light  Curve  

Brightness  

Time  

100.3%  

99%  

Transit  100%  

Star  +  Planet  Star  

Eclipse  depth  is  different    at  different  wavelengths  

Eclipse  Spectrum  ≈  (Rp/R*)2  (Tsurf  -‐  Ttrop)/T*  

Thermal  Phases  

Thermal  Light  Curve  

Brightness  

Time  

100%  

Transit  Eclipse  

100.3%  

Star  +  Planet  Star  

100.1%  

Phase  Amplitude  ≈  (Rp/R*)2  (Tday  -‐  Tnight)/T*  

Eclipse  Spectroscopy    vs.  Phase  Varia&ons  

•  Differences  in  temperature    – Ver&cal  (33-‐200  K)  – Zonal  (60-‐2000  K)  

•  Spectroscopy  has  to  achieve  S/N  with  rela&vely  narrow  bandwidth  (R>10)  

•  Phase  varia&ons  require  long-‐term  stability  

Predic&ng  vs  Measuring    Planetary  Climate  

Model  Inputs  •  Insola&on  •  Eccentricity  •  Obliquity  •  Surface  Albedo  •  Greenhouse  Gases  •  Specific  Heat  Capacity  •  Surface  Gravity  •  Surface  Pressure  •  Thermal  Iner&a  

Model  Outputs  •  Emiang  Temperature  •  Temperature  Gradients  •  Diurnal  Response  •  Seasonal  Response  •  Cloudiness  •  Surface  Temperature  •  Precipita&on