The researchers from the University of Warwick and Cambridge studied the dust and debris surrounding a white dwarf called GD6, observing it with the Hubble Space Telescope and the large Keck Telescope in Hawaii, Xinhua reported Thursday.
The white dwarf GD61 is a small but incredibly dense burnt star that lies 170 light years away from earth.
The US journal science said that the researchers have found an excess of oxygen, which indicates the debris once had been part of a bigger body originally composed of 26 percent water by mass.
In contrast, only 0.023 percent of the Earth's total mass is water.
"Two things -- a rocky surface and water are keys in the hunt for habitable planets outside our solar system. It is very exciting to find them together for the first time outside our solar system," said co-author Boris Gansicke from the University of Warwick.
The researchers suggest that the water detected around the white dwarf GD61 came from a minor planet, which is at least 90 km in diameter. Once this minor planet orbited the parent star before it became a white dwarf.
About 200 million years ago, GD61 entered its death throes and became a white dwarf. Its parts still survive in the form of dust and debris in the planetary system.
The water-rich minor planet was pulled out of its regular orbit and plunged into a close path, where it was shredded by the gravitational force of the star.
"The presence of water in a large asteroid means the building blocks for habitable planets existed. It might be still existing in the GD61 system. Water can also be found around substantial number of similar parent stars," said lead author Jay Farihi from the University of Cambridge.
Farihi said, "Our results demonstrate that there was a definite potential for habitable planets in this exoplanetary system."
"Our Sun after six billion years from now will collapse and possibly evolve into a white dwarf. Therefore, it's a look into our future," said Gansicke.
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