Upload
rylan-mich
View
218
Download
2
Embed Size (px)
Citation preview
Photochemistry in the Atmospheres of Hot Jupiters
Yuk L. Yung1, Mao-Chang Liang2, Michael Line1 and Giovanna Tinetti3
1Division of Geological and Planetary Sciences, California Institute of Technology, USA2Research Center for Environmental Changes, Academia Sinica, Taiwan3University College London, UK.
Molecules in the Atmospheres of Extrasolar planetsParis, Nov 19-21, 2008
Start with colder planets
HD209458b H2O, CO, CO2, CH4 and hydrocarbons Sulfur species, Nitrogen species
Lessons from solar system
Today’s OutlineToday’s Outline
Chemical processes
• Chemical composition different from that of Jupiter– CO and H2O are abundant; CH4 not abundant
• UV radiation a lot more enhanced– Can break up more molecules– Boost subsequent chemical reactions
• Performing photochemical calculation for HD 209458b
Properties of HD 209458b
• “Best known” planet– First discovered transiting planet (Henry et al. 2000)
– First atmosphere detection (Charbonneau et al. 2001)
– First exosphere detection (Vidal-Madjar et al. 2003)
• Orbiting HD 209458 G0V-type star– ~0.05 AU or 3.5 days
• Inclination angle ~85• Radius 1.54 RJ and mass 0.68 MJ
One-dimensional photochemical model
• Solving mass continuity equation–
–
– Kzz = K0n-, 0.5
• Temperature profile from thermochemical calculation
• Chemical reactions from, for example, Yung and DeMore (1999)
iizzii
iatm
zz
i
iizzi
ii wn
T
KD
z
Tn
H
K
H
DnKD
z
n+
++∂∂
−+−+∂∂
−= ])1(
[)()(αϕ
iiii LPzt
n−=
∂∂
+∂∂ ϕ
Atomic Hydrogen
H Productionhigh H/H2 ratio
H2O + h H + OH OH + H2 H2O + H
Net: H2 + h 2H
H2O Production
CO + h C + OO + H2 OH + HOH + H2 H2O + H
Net: CO + 2H2 + h C + H2O + 2H
Hydrocarbons
CO + h C + OC + H2 + M 3CH2 + M2 3CH2 C2H2 + 2HC2H2 + H + M C2H3 + MC2H3 + H2 C2H4 + HC2H4 + H + M C2H5 + MC2H5 + H 2CH3
CH3 + H + M CH4 + M
CH4 Production
bottleneck
2[CO + h C + O]2[C + H2 + M 3CH2 + M] 3CH2 + 3CH2 C2H2 + 2HC2H2 + H + M C2H3 + MC2H3 + H2 C2H4 + HC2H4 + H + M C2H5 + MC2H5 + H 2CH3
2[ CH3 + H + M CH4 + M]2[ O + H2 OH + H]2[ OH + H2 H2O + H]2[ H + H + M H2 + M]
net 2CO + 3H2 CH4 + 2H2O
Conclusions
Common photochemistry: hundreds of molecules, thousands of reactions
Similar Processes: Catalytic cycles, evolution, hydrodynamic escape, thermal inversion
Advice to modelers:
Dans ce meilleur des mondes possibles … tout est au mieux.
(In this best of possible worlds … all is for the best.)
Advice to observers:
Dieu n’est par pour les gros bataillons, mais pour ceux qui tirent le mieux.
(God is on the side not of the heavy battalions, but of the best shots.)
Acknowledgements
• NASA and ESA
• Yung’s Group at Caltech
• Liang Ph.D. Thesis 2005
• Meadows et al. 2008
• Yung and DeMore (1999) Book
Common photochemistry: hundreds of molecules, thousands of reactions
Similar Processes: Catalytic cycles, evolution, hydrodynamic escape, thermal inversion
Advice to modelers:Dans ce meilleur des mondes possibles … tout est au mieux(In this best of possible worlds … all is for the best.)
Advice to observers:Dieu n’est par pour les gros bataillons, mais pour ceux qui tirent le mieux.
(God is on the side not of the heavy battalions, but of the best shots.)
ConclusionsConclusions