Exoplanet Excites Earthly Observers

Astronomers have measured the infrared spectrum of a planet outside our solar system for the first time ever, though they failed to find what they were looking for: signs of water or other molecules necessary for life.

But the failure to find water does not necessarily mean that it does not exist, said one of the team’s leaders, Assistant Professor of Astronomy David Charbonneau.

Charbonneau said his team can’t explain the missing water. “It’s a bit of a puzzle,” he said.

The team examined “HD 189733b,” a large, gaseous planet similar to Jupiter. It is 60 light-years from Earth.

The findings were made using NASA’s Spitzer Space Telescope, the “infrared cousin of the Hubble,” which is able to see the infrared spectrum of faraway stars, Charbonneau said.

“What we’d love to do is to take a picture of the planet,” he said.

“We’re not able to do that, so we play a trick,” he added, referring to the technique of measuring the planet’s infrared spectrum.

Despite the failure to find water, Charbonneau said he believes the high pressure on the hot, massive planet could have brought hydrogen and oxygen together to create water.

“At those pressures, they almost certainly would combine to make water,” he said, noting that it would be surprising if there wasn’t water since “water is so easy to make.”

Charbonneau said there could still be water on HD 189733b, but that dark clouds made of silicates in the planet’s atmosphere might make it impossible to see through.

On Earth, silicates are found in rocks, but on much hotter planets, Charbonneau said, silicates have been found in dark clouds.

A second planet, HD 209458b, studied by L. Jeremy Richardson of NASA’s Goddard Space Flight Center, shows signs of silicates in the atmosphere, according to a press release from the Harvard-Smithsonian Center for Astrophysics.

Future plans to study HD 189733b and other similar planets are underway, Charbonneau said.

Sara Seager, a professor of earth, atmospheric, and planetary sciences at MIT, said more accurate results will depend on a better telescope.

Seager said the James Webb Space Telescope, which will be launched in 2013 and orbit the earth at a height of one million miles, will have a lens seven times bigger than that of the Spitzer telescope.

The study by Charbonneau and co-author Carl Grillmair of the Spitzer Science Center will be published in an upcoming issue of The Astrophysical Letters, according to the press release.