A lesser-known NASA probe has found vast quantities of water vapor circling an aging, massive star, a cloud that likely comes from a melting belt of icy comets that could be remnants of a distant planetary system there.

The finding at a star called CW Leonis suggests the star is the center of a late-stage solar system, and that water might be prevalent in planetary systems beyond our own. As water is a key ingredient for life, the finding supports the idea that there might be life beyond our solar system.

"This is first detection of water in a putative other solar system," said Gary Melnick of the Harvard-Smithsonian Center for Astrophysics, who headed up the study that yielded the results.

No one had anticipated the result, but it encourages those who have sought planets and signs of life beyond our solar system.

The water was detected by a spectrometer aboard the Submillimeter Wave Astronomy Satellite (SWAS), designed to study chemicals found in interstellar gas clouds. Melnick said the water vapor was vaporized from the surfaces of orbiting comets.

Melnick and his colleagues think comets are the best and only explanation for the presence of the water at CW Leonis, located in the constellation Leo about 500 light years away. Comets in our solar system are frozen ice balls mixed with rock, thought to be leftovers from the formation of the outer planets. The comets inferred at CW Leonis strongly suggest a solar system or its relics there.

Our own Sun is known to boil water and other gases off comets when they pass through the inner solar system. And many researchers think that water from comets may have helped create Earth's oceans, making life here possible.

The quantity of water found is estimated at 10,000 times the water in all the Earth's oceans.

CW Leonis is a dying star, expanding and blazing even hotter than before. As a result, it likely is frying any planets in its orbit as well as comets in the outer reaches of its system. That leaves burnt cinders of planets, the thinking goes, and pushes water vapor to the edges of its system -- the water vapor that SWAS detected.

Alan Boss, an astronomer at the Carnegie Institution, likened the CW Leonis system to a "cosmic Phoenix" that pushes out its ashes and water that go on to seed the interstellar medium where new stars and planetary systems form.

"Water is being pushed outwards by star's wind where it eventually collects into clouds of stars and dust that will form next generation of stars and planetary systems," he said.

Plenty of water already has been found in the universe, although never at a stellar body. And in 1984, scientists found signs of evaporating comets falling into the central region of a star called Beta Pictoris. But there was no water itself detected.

The finding at CW Leonis marks the first time astronomers have found water within a suspected solar system other than our own, water that is a strong indication of comets.

CW Leonis is a carbon-rich star, which means Melnick and his colleagues expected that any oxygen there would be trapped primarily in carbon monoxide molecules comprised of an oxygen atom and a carbon atom bound together. So the water (comprised of two hydrogen atoms bonded to an oxygen atom) finding surprised his team.

SWAS found so much water that Melnick thinks it could only be explained by several hundred billion comets at distances from the star between 75 and 300 times the distance of Earth from the Sun.

"That sounds like a lot," said Saavik Ford, a graduate student at Johns Hopkins University in Baltimore who is a co-author of the article reporting the discovery. "But the total mass required of this swarm of orbiting comets is similar to the original mass of the Kuiper Belt, a collection of comets that orbits our own Sun beyond the orbit of Neptune."

CW Leonis is burning so intensely now that it is capable of vaporizing several billion comets all at once, Ford said.

Because the star is further along in its lifetime than our Sun, Melnick and his colleagues see the CW Leonis system as an apocalyptic picture of our future.

Six billion years from now, our Sun will become a giant star like CW Leonis, with its power output increasing 5,000 fold, said David Neufeld, a Johns Hopkins astronomer who worked with Melnick on the study. If Melnick and Neufeld's vision of CW Leonis is accurate, our system's future looks like a rock sauna.

Once our star starts expanding and heating up, a wave of water vapor will spread throughout the solar system as the Sun evaporates water from Earth's oceans and bodies beyond Earth. "Even Pluto will be vaporized leaving just a cinder of hot rock," Neufeld said.

Indirect evidence of solar systems beyond ours has piled up at a rapid rate in just the past five years. Using space-based telescopes, astronomers have found disks of gas and dust en route to becoming solar systems in gas nebulas. Astronomers also have found "wobbling" stars being tugged gravitationally by nearby objects, evidence for more than 50 planets orbiting stars beyond our solar system.

But the wobble technique can only point to large planets orbiting close to stars they orbit. So Melnick hopes the spectroscopic approach will fill in blanks left by the wobble approach.

"Compositional spectroscopy like we've seen in today's findings gives us an opportunity to study smaller objects that are not very massive and may not reside very close to a star," he said, "and give us insight into total architecture of a system."