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Keck scientists find water vapor on distant planet

By Jim Borg

LAST UPDATED: 12:45 p.m. HST, Mar 14, 2013

WAIMEA » A team of astronomers using the Keck Observatory has widened the window on the study of alien worlds, finding water vapor in the atmosphere of a giant planet around a distant star.

While liquid water is seen as requirement for life as we know it, the planet in question is forbiddingly hostile, with a mass several times that of Jupiter, no solid surface under the atmosphere, and a temperature of about 1,000 degrees Fahrenheit, scientists said today. The water exists as hellishly hot steam.

Still, the finding shows what astronomers can accomplish today using the Keck’s light-gathering power, adaptive optics to counter the blur of our atmosphere, and highly sophisticated instruments that can discern chemical fingerprints at vast distances.

“This is the sharpest spectrum ever obtained of an extrasolar planet,” said Bruce Macintosh, an astronomer at Lawrence Livermore National Laboratory in California and a co-author of the study, in a news release. “This shows the power of directly imaging a planetary system — the exquisite resolution afforded by these new observations has allowed us to really begin to probe planet formation.”

The paper will appear online today in Science Express, and on March 22 in the journal Science.

The findings were also announced here today in conjunction with the 20th anniversary of the Keck Observatory. About two dozen scientists, including Macintosh, are convening at the beachfront Fairmont Orchid hotel to discuss the science made possible by Keck.

The planet is one of four gas giants orbiting a star called HR 8799, 130 light-years from Earth. The authors and their collaborators discovered this planet, HR 8799C, and its three companions back in 2008 and 2010. 

The study, the most detailed examination yet of the atmosphere of a Jupiter-size planet beyond our solar system, strengthens the possibility one day of finding “biomarkers,” chemicals such as oxygen, ozone, carbon dioxide and methane that strongly suggest biological processes.

On HR 8799 planet C, the astronomers found water vapor and carbon monoxide.

Quinn Konopaky, an astronomer with the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto, credited the Keck Observatory’s advanced instrumentation, along with groundbreaking observational and data-processing techniques. The angle of the planetary system also reveals the planets like merry-go-round horses.

“We can directly image the planets around HR 8799 because they are all large, young, and very far from their parent star,” said team member Christian Marois, an astronomer at the National Research Council of Canada. “This makes the system an excellent laboratory for studying exoplanet atmospheres.”

Key to the observations was an instrument called OSIRIS, a spectrograph designed to work with the Keck adaptive optics system. It uses an array of tiny lenses to sample a rectangular patch of the sky and produces chemical signatures at up to 3,000 spots simultaneously.

 “With this level of detail, we can compare the amount of carbon to the amount of oxygen present in the atmosphere, and this chemical mix provides clues as to how the planetary system formed,” says coauthor Travis Barman, an astronomer at the Lowell Observatory in Flagstaff, Ariz.

Bottom line: the planet formed in a way much like Jupiter, Saturn, Uranus and Neptune.

“The fact that the HR 8799 giant planets may have formed the same way our own giant planets did is a good sign,” said Macintosh. “That same process also made the rocky planets close to the sun.”

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