A group of astronomers have found the first evidence of water outside our solar system, in the shattered remains of an asteroid orbiting a dying star, or white dwarf.
Scientists from the University of Warwick and the University of Cambridge used observations obtained with NASA’s Hubble Space Telescope and large telescopes from the W. M. Keck Observatory in Hawaii, and found an excess of oxygen in the dust and debris surrounding the white dwarf star GD 61, located 170 light years from Earth.
“The finding of water in a large asteroid means the building blocks of habitable planets existed – and maybe still exist – in the GD 61 system, and likely also around substantial number of similar parent stars,” said Jay Farihi, of the University of Cambridge and the lead author of the study, published in Science on Friday. “Our results demonstrate that there was definitely potential for habitable planets in this exoplanetary system.”
Scientists said that the finding of excessive oxygen in the debris indicated that the remains had once been part of a bigger asteroid, a rocky world that was originally composed of 26 percent water by mass. In comparison, only about 0.023 percent of the Earth’s mass is water.
According to the scientists, the Earth's oceans came long after our planet had formed, most likely when water-rich asteroids in the solar system crashed into our planet. And, the new discovery shows that the same "water delivery system” could have occurred in this distant, dying star’s solar system.
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“This oxygen excess can be carried by either water or carbon, and in this star there is virtually no carbon – indicating there must have been substantial water,” Boris Gänsicke of the University of Warwick, said in a statement.
The researchers suggest that the watery asteroid was probably at least 90 kilometers (56 miles) in diameter and it orbited its parent star before the latter became a white dwarf about 200 million years ago.
According to scientists, this is the first time that both water and a rocky surface -- two key ingredients for habitable planets -- have been found together beyond our solar system.
The researchers described the discovery as a “look into our future” as, billions of years from now, alien astronomers studying the rocky remains around our burned out sun might reach a similar conclusion that earthly planets once circled our parent star.
“This planetary graveyard swirling around the embers of its parent star is a rich source of information about its former life,” Gänsicke said. “In these remnants lie chemical clues which point towards a previous existence as a water-rich terrestrial body.”
Observations of 12 destroyed exoplanets orbiting white dwarves have been carried out so far, but this is the first time the signature of water has been found, scientists said.