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A team of astronomers has created the first map of an extrasolar planet, HD 189733b, located approximately 60 light-years from Earth.
By measuring brightness and other data collected over time by the Spitzer Space Telescope, the scientists constructed a map of the brightness of the planet's surface. The telescope's location in space combined with its infrared technology provided information about the planet's hot and cold spots not possible with any imaging technology available today, the scientists said.
Spitzer's technology could be used to map Earth-like planets – like the recently-discovered Gliese 581c – to determine information about their atmospheres, the scientists said.
This computer-generated animation begins with a rough map of the planet HD 189733b, as measured with NASA's Spitzer Space Telescope. Astronomers obtained a series of pole-to-pole strips in infrared light, then wrapped that map around a 3-d surface to show what the planet looks like. They found that the planet has a "hotspot" offset from high noon.
Credit: NASA/JPL-Caltech.
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The planet, which was discovered in 2005, was selected because it is the closest transiting planet to Earth (meaning we can see it pass in front of and behind its star), and its orbit can be seen from Earth. However, the planet is too far to take direct photographs, which led to some creative map making.
"(Creating an image directly) would require such incredible resolution that it's beyond any foreseeable experiments," said Dr. David
Charbonneau, professor of astronomy at Harvard University and a co-author on the paper.
The data will be published in the May 10 issue of Nature.
Jonathan Fortney, a Spitzer Fellow at the NASA Ames Research Center, and a co-author on the paper said that the field of exoplanetary study is still in its early stages, and that only two years ago, there was little data available.
"[This new map] really allows us to start talking about the weather of this planet, which is a huge leap compared to where we were two years ago and now we're starting to talk about weather," he said.
However, because the team is only able to measure brightness as seen from the side-to-side rotation, they have to make assumptions about what the differences in brightness are with respect to latitude.
Once the James Webb telescope comes online in 2013, Charbonneau said, studying exoplanets will become more advanced, and in particular, it will be easier to find Earth-like planets.
"Lo and behold if you had a super-Earth... with the James Webb telescope you could make a map of the actual Earth-like planet," he said. "In particular, you could look for properties of the atmosphere of that planet."
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