Photochemistry in the Atmospheres of Hot Jupiters

1. 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, USA 2Research Center for Environmental Changes, Academia Sinica, Taiwan 3University College London, UK. Molecules in the Atmospheres of Extrasolar planets Paris, Nov 19-21, 2008

2. Today’s Outline • Start with colder planets • HD209458b • H2O, CO, CO2, CH4 and hydrocarbons • Sulfur species, Nitrogen species • Lessons from solar system

9. HD209458b

10. 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

11. 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

12. One-dimensional photochemical model • Solving mass continuity equation • Kzz = K0n-,   0.5 • Temperature profile from thermochemical calculation • Chemical reactions from, for example, Yung and DeMore (1999)

13. Temperature profiles Barman et al. 2002 Fortney et al. 2003 F/2 Jupiter F/2 F/4 Seager et al. 2000

14. Model atmosphere

16. Atomic Hydrogen H Production high H/H2 ratio H2O Production CO + h  C + O O + H2  OH + H OH + H2  H2O + H H2O + h  H + OH OH + H2  H2O + H Net: H2 + h  2H Net: CO + 2H2 + h  C + H2O + 2H

17. CH4 Production CO + h  C + O C + H2 + M  3CH2 + M 2 3CH2  C2H2 + 2H C2H2 + H + M  C2H3 + M C2H3 + H2  C2H4 + H C2H4 + H + M  C2H5 + M C2H5 + H  2CH3 CH3 + H + M  CH4 + M bottleneck Hydrocarbons

18. 2[CO + h  C + O] 2[C + H2 + M  3CH2 + M] 3CH2 + 3CH2 C2H2 + 2H C2H2 + H + M  C2H3 + M C2H3 + H2  C2H4 + H C2H4 + H + M  C2H5 + M C2H5 + 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

25. N2 HCN NH3 NH2 N CH3NH2 CN NO NH

27. S2 SH S H2S SO HSO S3 SO3 S5 S4 S6 SO2 S8 H2SO4

31. [Friedson et al., Icarus, 2002]

35. 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.)

36. Acknowledgements • NASA and ESA • Yung’s Group at Caltech • Liang Ph.D. Thesis 2005 • Meadows et al. 2008 • Yung and DeMore (1999) Book

37. Back-up slides

38. OCS OCS

41. 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.)