Water Detected on 5 Distant Jupiter-like Worlds

The signature of water has been detected in the atmospheres of five distant, Jupiter-like planets, NASA reported Tuesday.

The agency's Hubble Space Telescope was used to observe the planets, and astronomers were for the first time able to conclusively measure and compare the water profile and the intensity of its detectable signature among multiple worlds.

"We're very confident that we see a water signature for multiple planets," said Avi Mandell, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "This work really opens the door for comparing how much water is present in atmospheres on different kinds of exoplanets, for example hotter versus cooler ones."

The planets where water was detected all orbit nearby stars, however the strength of their water signature varies. The planets where NASA reports water in the atmosphere are: WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b.

Research teams used an infrared signal on the Hubble's Wide Field Camera 3 to observe the exoplanets. If the chemical signature of water is present, it will be observable on the infrared spectrum. The consistency of the water signature among the planets convinced the researchers what they were seeing was indeed water in the atmosphere, and comparing the shapes and intensities of the infrared profiles have given them workable data to reach more solid conclusions about the chemical make-up of the distant worlds.

"To actually detect the atmosphere of an exoplanet is extraordinarily difficult. But we were able to pull out a very clear signal, and it is water," said Drake Deming of the University of Maryland, who's team reported on HD209458b and XO-1b in an earlier study in the Astrophysical Journal. The current study is presented in the Tuesday's issue of the same publication.

While the scientists are confident they have detected water on the distant planets, they said they were surprised by the relatively weak signal the water gave off. The scientists suspect a thin layer of haze in the atmospheres of the exoplanets to play a part in why the chemical signature appears so weak; they likened the presence of haze to fog in a photograph, noting that either can make colors appear muted.

The five exoplanets - known as "hot Jupiters" -  have characteristics similar to Jupiter but because of their close proximity to their host stars, they each have much hotter surface temperatures than the largest planet in our solar system.

Spotting these planets was difficult because of the tremendous distance away these planets are from the Hubble telescope, which is only able to spot these worlds if it catches them as they pass across their host stars.