Hubble Telescope Finds Evidence of Water on Five Exoplanets

 Exoplanets  

Scientists have found evidence of water vapor in the atmospheres of five 'hot Jupiter' planets. Refining their ability to find water vapor could be key to the search for life on other planets.

Astronomers have discovered water vapor in the atmospheres of five planets beyond the solar system. Using the powerful eye of NASA's Hubble Space Telescope, two teams of scientists have found faint signatures on the Jupiter-like exoplanets.

The five planets -- WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b -- orbit nearby stars. The strengths of their water signatures varied. WASP-17b, a planet with an especially puffed-up atmosphere, and HD209458b had the strongest signals. The signatures for the other three planets, WASP-12b, WASP-19b and XO-1b, also are consistent with water according to NASA.

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The presence of atmospheric water was reported previously on a few exoplanets orbiting stars beyond our solar system, but this is the first study to conclusively measure and compare the profiles and intensities of these signatures on multiple worlds.It heralds a expansion from merely hunting for planets and putting them into bins by mass or distance from their stars to studying their atmospheres. The new research could help scientists refine how they look for key signatures that a planet could sustain life, as well as improve our understanding of where and how the planets formed.

Armed with a fresh approach to using the Hubble Space Telescope, astronomers are opening “the era of characterization,” says Avi Mandell, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland., and the lead author of one of two research papers reporting the results.

The studies were part of a census of exoplanet atmospheres led by L. Drake Deming of the University of Maryland in College Park. Both teams used Hubble's Wide Field Camera 3 to explore the details of absorption of light through the planets' atmospheres. The observations were made in a range of infrared wavelengths where the water signature, if present, would appear. The teams compared the shapes and intensities of the absorption profiles, and the consistency of the signatures gave them confidence they saw water. The observations demonstrate Hubble's continuing exemplary performance in exoplanet research.

"These studies, combined with other Hubble observations, are showing us that there are a surprisingly large number of systems for which the signal of water is either attenuated or completely absent," said Heather Knutson of the California Institute of Technology, a co-author on Deming's paper. "This suggests that cloudy or hazy atmospheres may in fact be rather common for hot Jupiters."

While these planets are not candidates for life, water vapor is of keen interest for biological reasons, since water is a necessary ingredient for organic life. Moreover, water, especially in conjunction with measurements of carbon monoxide, can yield clues about whether a planet formed close to its star or out beyond what often is called the snow line. There, temperatures are so cold that water becomes ice and gets incorporated into a planet's core.

Both reports noted that the signatures water vapor gave were weaker than models had predicted. It's a phenomenon researchers have noted since they first detected a chemical element in the atmosphere of an extrasolar planet – sodium in 2002. Researchers attribute the lower-than-expected readings to clouds or haze in the atmospheres.

Deming's team used Hubble to stare at a nearby star, but only briefly; it was designed to observe faint objects and couldn't remain trained on a bright planet-hosting star for long because elements in the telescope would become overloaded with light, Deming explains.

The newer approach in effect sweeps the light across the camera until all of the individual elements in the detector have had their fill of light.

“This greatly increases the efficiency and the light gathering,” Deming says, leading to far-more precise measurements. With that precision and a deeper understanding of the camera's quirks and how to adjust for them comes greater confidence in the measurements it makes.

SOURCE  Christian Science Monitor

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