Astronomers Detect Water in Atmosphere of Distant Planet

W. M. Keck Observatory press release

A team of international scientists using the W. M. Keck Observatory has made the most detailed examination yet of the atmosphere of a Jupiter-size planet beyond our Solar System.

According to lead author Quinn Konopacky, an astronomer with the Dunlap Institute for Astronomy & Astrophysics, University of Toronto and a former Lawrence Livermore National Laboratory (LLNL) postdoc, “We have been able to observe this planet in unprecedented detail because of Keck Observatory’s advanced instrumentation, our ground-breaking observing and data processing techniques, and because of the nature of the planetary system.” The paper appears online March 14th in Science Express, and March 22nd in the journal Science.

“This is the sharpest spectrum ever obtained of an extrasolar planet,” said co-author Bruce Macintosh, an astronomer at LLNL. “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.”

Early HR8799
Artist’s rendering of the planetary system HR 8799 at an early stage in its evolution. Credit: Dunlap Institute for Astronomy & Astrophysics

The team, using the OSIRIS instrument fitted on the mighty Keck II telescope on the summit of Mauna Kea, Hawaii, has uncovered the chemical fingerprints of specific molecules, revealing a cloudy atmosphere containing water vapor and carbon monoxide. “With this level of detail,” says coauthor Travis Barman, an astronomer at the Lowell Observatory, “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.”

There has been uncertainty about how planets in other solar systems formed, with two leading models, called core accretion and gravitational instability. When stars form, they are surrounded by a planet-forming disk. In the first scenario, planets form gradually as solid cores slowly grow big enough to start absorbing gas from the disk. In the latter, planets form almost instantly as parts of the disk collapse on themselves. Planetary properties, like the composition of a planet’s atmosphere, are clues as to whether a system formed according to one model or the other.

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