The technique that found atmospheric water on the planet outside our solar system could help find planets like Earth throughout the universe, they said.
"Planets like tau Bootes b, which are as massive as Jupiter but much hotter, do not exist in our solar system," Penn State research associate Chad Bender said. "Our detection of water in the atmosphere of tau Bootes b is important because it helps us understand how these exotic hot-Jupiter planets form and evolve."
Water vapor has previously been detected on a handful of other planets, using a technique that works only if a planet has an orbit that transits, or passes it in front of its star, when viewed from Earth.
The researchers said they used a new technique using infrared observation to detect water on planets that had resisted probing using earlier methods.
"We now are applying our effective new infrared technique to several other non-transiting planets orbiting stars near the Sun," Bender said.
"These planets are much closer to us than the nearest transiting planets, but largely have been ignored by astronomers because directly measuring their atmospheres with previously existing techniques was difficult or impossible," he said.
The discovery has been published in the Astrophysical Journal Letters.