The Exotic Atmospheres of Hot Jupiter-like Planets

Jonathan J. Fortney^1,2 and Mark S. Marley
NASA Ames Research Center
¹Spitzer Fellow ²UC Santa Cruz in January

Defining Giant Hot Jupiter-like Exoplanets as an Astronomical Class of Objects

Studying primary and secondary eclipses allows scientists to learn about hot Jupiter-like exoplanets' global structure, atmospheres, and eccentricity and obliquity.

• Infrared thermal emission can be measured around the time of secondary eclipse by Spitzer
• Absorption of stellar light by a planet's atmosphere can be measured by Hubble and Spitzer during the transit (primary eclipse)
• The scientists are modeling the exotic atmospheres of the "hot Jupiter" class of exoplanets
• 25 have been seen to transit their parent stars
• Model atmospheres of these planets are computed to better understand these complex atmospheres
• Atmospheric chemistry is intricate--the abundances of atoms and molecules are predicted over a wide range of temperature and pressure
• H₂O, CO, CH₄, Na, K, TiO, and VO are expected to be found in these H/He-dominated atmospheres
• They try to understand the deposition and redistribution of energy
• Are the permanent night sides cold?

Infrared thermal emission can be measured around the time of secondary eclipse by Spitzer. Click image for larger view.

Implications In order to better understand our own Solar System and those that exist beyond our sun's influence, the scientists are seeking to understand giant planets as a class of astronomical objects that can be defined both in our solar system and others. Detailed model atmospheres, which utilize our best understanding of atmospheric chemistry, the opacities of atoms and molecules, cloud physics, radiative transfer, and atmospheric dynamics, are absolutely essential for:

1. predicting what observations should be made now and in the future
2. interpreting observations once data are in hand

Absorption of stellar light by a planet's atmosphere can be measured by Hubble and Spitzer during the transit (primary eclipse). Click image for larger view.

Significance to Solar System Exploration

• What would Jupiter's atmosphere be like if it was moved 100+ times closer to the Sun?
• Are these planets like Jupiter and Saturn?
• Can their atmospheres tell us if they formed via a common mechanism?
• We were able to predict and understand the incredible diversity we are already seeing with a small amount of data.

Global temperature map for exoplanet HD 189733b. Click image for larger view.

• Some planets have hot stratospheres and large day/night temperature contrasts of ~1500 K
• Setting the Stage for the Future:
• Jupiter-mass and Neptune-mass planets discovered by radial velocity and transit surveys are being characterized with Hubble and Spitzer
• Earth-mass and super-Earth planets discovered by radial velocity surveys, Kepler, and COROT will be characterized in the Spitzer warm mission, Hubble, and the James Webb Space Telescope
• This sets the stage for detailed characterization by TPF or other large space platforms

Written by Samantha Harvey

For further information about science highlights and having your research highlighted, please contact Samantha Harvey at NASA's Jet Propulsion Laboratory, Samantha.K.Harvey@jpl.nasa.gov.

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