I absolutely love the image below, so I decided to run it at full size although it doesn’t quite fit the column width. You’re looking at the result of recent work from the California & Carnegie Planet Search team, which used data from the Spitzer Space Telescope to produce what is probably the most accurate image yet of an exoplanet. It’s not an actual photographic image, of course, but it’s better than an artist’s interpretation because it’s based on highly realistic simulations.
The planet in question is HD 80606b, which circles a star about 200 light years from Earth. This is a highly interesting place, some four times the mass of Jupiter and moving within a 111-day orbit around its star. What makes it stand out is the incredible eccentricity of its orbit. We’re talking about a world that for most of its orbit is at distances that would be between Venus and Earth here in our system. But then it swoops in ever closer to its primary until it closes to within 0.03 AU, an encounter it experiences for less than a day.
Image: The planet HD80606b glows orange from its own heat in this computer-generated image. A massive storm has formed in response to the pulse of heat delivered during the planet’s close swing past its star. The blue crescent is reflected light from the star. Credit: D. Kasen, J. Langton, and G. Laughlin (UCSC).
The Spitzer observations took place during this period of closest approach, when a secondary eclipse (as the planet passed behind the star) allowed precise measurements that the researchers used to peg the temperatures on this world. To describe what happens at perihelion, I turn to Jonathan Langton, a UCSC postdoc, who discussed the matter in this news release. HD 80606b is, as you might imagine, a place of storms that defy the imagination, and planetary shockwaves:
“The initial response could be described as an explosion on the side facing the star,” Langton said. “As the atmosphere heats up and expands, it produces very high winds, on the order of 5 kilometers per second, flowing away from the day side toward the night side. The rotation of the planet causes these winds to curl up into large-scale storm systems that gradually die down as the planet cools over the course of its orbit.”
The image above was developed using software from UCSC’s Daniel Kasen, who tuned it to calculate radiative transfer processes that should catch the color and intensity of light this planet produces. Our friend Greg Laughlin, also at UCSC, calls these “…far more realistic than anything that’s been done before for extrasolar planets.” Up next: A possible transit on February 14, which could produce yet more information about this exotic world. Greg’s systemic site will be the place to watch for that.
Have a look at the orbit of this sizzling place in a figure from the paper that Greg just passed along:
Image: Orbital geometry of the HD 80606b system. The small dots show the position of the planet in its orbit at one hour intervals relative to the predicted periastron passage… The size of the parent star HD 80606 is drawn in correct relative scale to the orbit. Credit: Greg Laughlin.
What a place is HD 80606b. According to the paper on this work, the planet receives 828 times more irradiation at perihelion than at the most distant point in its orbit, with a temperature swing from 800 to 1,500 kelvin in a six hour period! The paper is Laughlin et al., “A Direct Observation of Rapid Heating of an Extrasolar Planet,” Nature 457, (29 January 2009), pp. 562-564 (abstract).