Exoplanetary Atmospheres: Atmospheric Dynamics of Irradiated Planets. PHY 688, Lecture 24 Mar 23, 2009

Exoplanetary Atmospheres: Atmospheric Dynamics of Irradiated Planets PHY 688, Lecture 24 Mar 23, 2009

Outline Review of previous lecture: atmospheric temperature structure of irradiated planets isothermal radiative region temperature inversion hot and very hot Jupiters Surface temperature gradients, winds, phases Radii Mar 23, 2009 PHY 688, Lecture 24 2

Previously in PHY 688 Mar 23, 2009 PHY 688, Lecture 24 3

From Lecture 17: H Phase Diagram temperature-pressure (T-P) diagram for isolated planets, temperature increases monotonically toward interior (Guillot 2006) Mar 23, 2009 PHY 688, Lecture 24 4

Effect of Irradiation balance between internal flux and flux incident from star T eff 4 = T int 4 + W T * 4 W dimensionless dilution factor ~ 10 3 incident light penetrates to depth τ pen, such that # " pen = W T * % $ for τ < τ pen, T eff is governed by irradiation and is constant isothermal, radiative region for τ > τ pen, T eff T int and rises monotonically with τ T int & ( ' 4 )1 Mar 23, 2009 PHY 688, Lecture 24 5

P-T Profiles of Hot Jupiters AU isothermal regions are radiative Mar 23, 2009 PHY 688, Lecture 24 6 (Fortney et al. 2007)

Cloud-Free Hot Jupiters May Show Only Tenuous Spectral Features emission from isothermal region appears blackbodylike between 8 15 micron no H 2 O?! Spitzer IRS spectrum of HD 189733b model from Burrows et al. (2006) H 2 O likely present, but not detectable Relative Flux note however, that these are extremely challenging observations! Mar 23, 2009 PHY 688, Lecture 24 7 (Grillmair et al. 2007)

Observational Challenges in Extracting Secondary Eclipse Light star-planet contrast: ~ 0.01 % in mid IR time-varying response of IR detectors telescope pointing stability variations in pixel response, positioning Mar 23, 2009 PHY 688, Lecture 24 8

Observational Challenges in Extracting Secondary Eclipse Light Spitzer IR detector response is not constant with time figure shows 3.6-micron background variation for TeES-4b observation 8 hours (Knutson et al. 2008) Mar 23, 2009 PHY 688, Lecture 24 9

Observational Challenges in Extracting Secondary Eclipse Light raw TrES-4b data Spitzer pointing varies 3.6- and 4.5-micron (In:Sb array) PSFs are barely Nyquist-sampled i.e., 2 pixel widths per PSF FWHM PSF-pixel positioning affects overall flux 5.8- and 8.0-micron arrays (Si:As) have a time-varying gain depends on incident flux 8 hours Mar 23, 2009 PHY 688, Lecture 24 10 (Knutson et al. 2008)

Observational Challenges in Extracting Secondary Eclipse Light raw TrES-4b data corrected data 8 hours Mar 23, 2009 PHY 688, Lecture 24 11 (Knutson et al. 2008)

Observational Challenges in Extracting Secondary Eclipse Light planet signal can not always be extracted: 16-micron flux measurement gives only an upper limit for TrES-4b raw TrES-4b data corrected data 8 hours Mar 23, 2009 PHY 688, Lecture 24 12 (Knutson et al. 2008)

Some Planets Require Extra Opacity at High Altitudes: TrES-4b extra opacity evident as excess >5 µm emission true for very hot Jupiters expected to cause a temperature inversion in the upper atmosphere κ extra additional opacity at high altitude P n fraction of incident flux redistributed to planet s night side Spitzer photometry of TReS 4b (Knutson et al. 2008) Mar 23, 2009 PHY 688, Lecture 24 13

Extra High-Level Opacity Creates an note 5.8µm flux peak region of a strong rovibrational band of water H 2 O Emission Signature (Burrows et al. 2007) Mar 23, 2009 PHY 688, Lecture 24 14

Temperature Inversions in Very Hot Jupiters i.e., stratospheres gas-phase TiO / VO? S from H 2 S photolysis? tholins, polyacetylenes, etc, produced through photolysis of CH 4 and NH 3? (Fortney et al. 2008) Mar 23, 2009 PHY 688, Lecture 24 15

The Earth s Stratosphere Earth s stratospheric clouds: an exception, not the rule Mar 23, 2009 PHY 688, Lecture 24 16

Hot and Very Hot Jupiters: pl vs. pm Planets distinction: based on lack or presence of high-level TiO/VO associated with a stratosphere cf. L vs. M stellar spectral types transition at around 0.04 0.05 AU equivalent separation from the Sun note dependences on: observed planetary hemisphere orbital phase for planets on very eccentric orbits HD 17156b, HD 80606b, HD 147506b (Fortney et al. 2008) Mar 23, 2009 PHY 688, Lecture 24 17

Outline Review of previous lecture: atmospheric temperature structure of irradiated planets isothermal radiative region temperature inversion hot and very hot Jupiters Surface temperature gradients, winds, phases Radii Mar 23, 2009 PHY 688, Lecture 24 18

Opacities of pm and pl Planets figure shows approximate pressure at photosphere (τ = 2/3) emission from pm photospheres comes from ~10 times lower pressures than in pl s <1-micron pm opacity likely due to higher TiO/VO abundance in the upper atmosphere temperature inversion >5-micron pm opacity produces shallower absorption signatures isothermal region Mar 23, 2009 PHY 688, Lecture 24 19 (Fortney et al. 2008)

Non-Uniform Planet Surface Brightness hot Jupiters are tidally locked to their host stars: orbital and rotation period are the same (~1 5 days) sub-stellar point does not change however, peak planet brightness does not coincide with moment of secondary eclipse redistribution of heat HD 189733 at 8 µm (Knutson et al. 2007) Mar 23, 2009 PHY 688, Lecture 24 20

Atmospheric Dynamics of Hot Jupiters Mar 23, 2009 PHY 688, Lecture 24 21

HD 189733b Brightness Map brightest spot is not at the substellar point brightest and faintest spot on HD 189733b are on the same hemisphere! temperature difference is ~350 K (Knutson et al. 2007) Mar 23, 2009 PHY 688, Lecture 24 22

Non-Uniformity in Brightness Depends on Incident Flux in fact, HD 189733b has a relatively homogenized daynight atmosphere ~350 K difference in temperature pl planet, no temperature inversion much larger day-night contrast inferred on υ And b, HD 179949b ~1400 K at υ And b pm planets, temperature inversions Mar 23, 2009 PHY 688, Lecture 24 23

Radiative (Newtonian) Cooling temperature disturbance relaxes toward radiative equilibrium exponentially, with time constant t rad for atmospheric P, T: t rad ~ P g c P 4"T 3 Mar 23, 2009 PHY 688, Lecture 24 24 (Fortney et al. 2008)

Radiative (Newtonian) Cooling temperature disturbance relaxes toward radiative equilibrium exponentially, with time constant t rad for atmospheric P, T: t rad ~ P g c P 4"T 3 Mar 23, 2009 PHY 688, Lecture 24 25 (Fortney et al. 2008)

Winds: U Cooling vs. Advection advection time scale t advec = R p /U R p planet radius U wind speed balance of cooling vs. advection decides wind speed U "T day night "T rad ~ 1# e #t advec / t rad winds of several km/sec (~ sound speed) expected from 2D and 3D dynamical models Mar 23, 2009 PHY 688, Lecture 24 26 (Fortney et al. 2008)

Winds: t rad /t advec Ratio Depends Also on Depth ratio is higher in the lower atmosphere especially in pm planets with stratospheres: t rad ~ P g c P 4"T 3 "T day night ~ 1# e #t advec / t rad "T rad smaller day-night contrast (more redistribution of heat) in: deeper layers pl planets Mar 23, 2009 PHY 688, Lecture 24 27 (Fortney et al. 2008)

Observations in Optical Reflected Light: Phases of Hot Jupiters Mar 23, 2009 PHY 688, Lecture 24 28 (Rowe et al. 2006)

HD 209458b: No Phase Variation Seen MOST satellite data HD 209458: original time series standard star: original time series 0 HD 209458: folded to P = 3.52 d 0.02 0 5 10 4 region of expected secondary eclipse HD 209458: folded, binned and zoomed Mar 23, 2009 PHY 688, Lecture 24 29 (Rowe et al. 2006)

Hot Jupiters are Very Dark in the Optical 500 800 nm opacity dominated by neutral alkali lines Mar 23, 2009 PHY 688, Lecture 24 30

Outline Review of previous lecture: atmospheric temperature structure of irradiated planets isothermal radiative region temperature inversion hot and very hot Jupiters Surface temperature gradients, winds, phases Radii Mar 23, 2009 PHY 688, Lecture 24 31

From Lecture 17: Radius vs. Mass: Comparison with Known Planets for polytropes R " M 1#n 3#n n = 1.5 for brown dwarfs n = 0.5 1.0 for 0.1 1 M Jup planets (n = 0: uniform density) icy/rocky cores in Neptune, Uranus? the hot Jupiter HD 209458b has a larger radius than nonirradiated planets H 2 O planet olivine (Mg,Fe) 2 SiO 4 planet (Guillot 2006) Mar 23, 2009 PHY 688, Lecture 24 32

Sizes and Compositions of Hot Jupiters (Charbonneau et al. 2007) Mar 23, 2009 PHY 688, Lecture 24 33

Are Bloated Hot Jupiters Younger? (Fortney et al. 2007) Mar 23, 2009 PHY 688, Lecture 24 34

Jupiter s Evolution in the Solar System Mar 23, 2009 PHY 688, Lecture 24 35

Radii of Hot Jupiters some large radii cannot be explained even by coreless planets with high-altitude stratospheres: younger age? resetting of the age through tidal heating? result of planetary migration? preferential evaporation of helium? (Fortney et al. 2007) Mar 23, 2009 PHY 688, Lecture 24 36