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A Hot Jupiter Simulation

June 18th, 2006

eggs in an egg carton

Last week, we had a one-day seminar on planets and planet formation at UC Santa Cruz that brought together researchers from both UCSC and NASA Ames. One of the talks was by Jonathan Fortney, who is currently a post-doctoral researcher in the Planetary Systems Branch of the Space Science Division at NASA Ames.

Fortney and his NASA Ames collaborator Mark Marley have a state-of-the-art radiative transfer code which can compute the emergent (and reflected) spectrum from a hot Jupiter. (See this recent post.) They’ve recently applied their code to compute how the intrinsic radiation from the flow pattern on the surface of the planet would look if you could resolve it with a pair of night-vision goggles. Jonathan writes:

Here’s an MPEG of the full 360 orbit of HD 209458b, in 36 10-degree increments. This is as seen from Earth. It’s the Cooper & Showman (2006) dynamical simulation, run through our radiative transfer solver.

Red is 5 microns, green is 3.3 microns, and blue is 2.2 microns. The Cooper and Showman model predicts a day side that is very similar to a blackbody, leading to a whitish appearance. On the night side, which is fairly cool, strong methane absorption knocks out the blue and green, leaving only red. I have artificially pumped up the red on the night side so that you can actually see it on the monitor. If you don’t, it’s a dark red which is hard to see compared to black–the night side has little flux compared to bright (hot) day.

Here’s a sequence of frames from the movie:

frames from Fortney's HD209458b animation

The animation draws on calculations described by Fortney, J. J., et al., 2006, “The Influence of Atmospheric Dynamics on the Infrared Spectra and Light Curves of Hot Jupiters”, which has been submitted to the Astrophysical Journal.

This is a big step forward for the “computational imaging” of extrasolar planets, and I’m really excited about the future directions that Fortney is planning to take these calculations. For starters, it will be very interesting to see the movie with the reflected light component added in. It will also be cool to place the point of view above a particular spot on the planet and animate the time-dependant flow pattern (the above movie rotates a single snapshot model of the planet, but it does not show the actual time evolution that is computed in Cooper and Showman’s hydrodynamical simulations). Animations of the time-dependant flow will start to bring exoplanets into the territory covered by the cloud-pattern movies that the Voyager and Cassini probes radioed to Earth as they flew past Jupiter. Finally, by using John Moore’s integrating sphere to produce the actual visible colors corresponding to individual computed spectra, it will also be possible to produce true visible light (rather than night-vision-goggle infrared) animations of the simulated surface of HD 209458 b and other hot Jupiters. (In particular, HD 80606!)

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