Washington: Astronomers have discovered a still-forming alien solar system having enough water that can fill Earth's oceans several thousand times over a finding they say strengthens the idea that comet impacts might have delivered most of the water on the planet.

The discovery marks the first time astronomers have detected water in a dusty planet-forming disk so far from its central star, in the frigid region where comets are born.

It has been thought that comet impacts may have delivered most of Earth's water, now the new study hints that alien planets may commonly acquire oceans in the same way, the
researches said.

"We now know that large amounts of water ice are available in planet-forming disks, ready to be incorporated in comets," said Michiel Hogerheijde of Leiden Observatory in the Netherlands, the study's lead author.

"Ultimately, some of this water may end up on Earth-like planets that form completely dry but this way may end up with life-supporting oceans," Hogerheijde said.

Using the Herschel Space Observatory of European Space Agency, the researchers found the young star, which is located about 175 light-years away in the constellation Hydra, and named it 'TW Hydrae'.

TW Hydrae is an orange dwarf star, slightly smaller and dimmer than our sun. It's only about 10 million years old, and is still surrounded by a disk of dust and gas that should one day coalesce to form planets, the researchers said.

They detected huge amounts of water - thousands of times more water than that found on Earth - in the freezing-cold outer reaches of this disk, far from TW Hydrae itself. The water out there is likely ice coating the innumerable tiny dust grains that swirl around in the disk, the team reported in the journal Science.

Ultraviolet radiation from TW Hydrae knocks some water molecules free from these icy grains, allowing Herschel to spot the light signature from the resulting vapour.

Astronomers have earlier found water vapour in the warmer and interior regions of other planet-forming disks. So, the team wasn't shocked to find evidence of water farther out.

"We had actually always suspected that this much water was hiding out in the cold reaches of disks like these," Hogerheijde said.

Thanks to Herschel, he added, "we can now for the first time detect the water vapour, and infer the presence and size of the hidden ice reservoir."

The TW Hydrae find suggests that ice-bearing comets may form commonly around other stars. The icy wanderers might thus have seeded oceans on many alien planets throughout the cosmos over the years, the researchers said.

"It does seem likely that life-supporting environments can form easily around other stars, now that we have found sufficient water ice to seed Earth-like planets with oceans,"
Hogerheijde said.

The finding could also help astronomers better understand solar system evolution and planet formation in a general sense, he added.