Knutson, who worked on mapping HD 189733 b in 2007, notes that the two maps pinpoint a similar location for the hot spot. "The really reassuring thing is that by using this different approach they come to a very similar conclusion," she says. Agol's group also revealed that the hot spot is located near the equator, as had been assumed in the one-dimensional longitudinal map. "The nice thing about their approach is that you can start to get some of that north-south information," Knutson says. "It's a really great shortcut to get around the fact that most of these planets are so far away that you can't really see them."
Unfortunately, few other known planets are as favorably positioned for such detailed study. For starters, HD 189733 b is closer to our solar system than all but a few known exoplanets. And it is a giant, about 14 percent larger in diameter than Jupiter, orbiting next to a host star that is about 20 percent smaller than the sun. Those dimensions, coupled with the planet's extreme heat, make for a relatively strong thermal signature that can be isolated from the radiation given off by the star alone. But future infrared observatories, such as NASA's massive James Webb Space Telescope, may be able to map additional exoplanets.
For now, the map that Agol calls a "first stab" at the secondary-eclipse technique is also an impressive résumé booster for Carl Majeau, an undergraduate student and the lead author of the new study. Majeau, who hails from Seattle, approached Agol for a project between school years at Columbia. "This was an idea that I thought would be cool to do with the data, but I just didn't have time to do it," Agol says. "At that point I think he had just finished his freshman year at Columbia, and he wanted a summer job."