#Signs of water detected in exoplanet s debris University of Warwick rightoriginal Studyposted by Anna Blackaby-Warwick on October 11 2013the remains of a water-rich rocky exoplanet have been discovered outside our solar system orbiting a white dwarf star 170 light years away. Using observations obtained with the Hubble Space Telescopeâ and the large telescopes of the W. M. Keck Observatory researchers found an excess of oxygenâ##a chemical signature that indicates that the debris had once been part of a bigger body originally composed of 26 percent water by mass. By contrast only approximately 0. 023 percent of the Earth s mass is water. Evidence for water outside our solar system has previously been found in the atmosphere of gas giants but this is the first time it has been pinpointed in a rocky body making it of significant interest in understanding of the formation and evolution of habitable planets and life. The dwarf planet Ceres contains ice buried beneath an outer crust and researchers have drawn a parallel between the two bodies. Itâ#believed that bodies like Ceres were the source of the bulk of our own water On earth. In the study published in Science researchers suggest it is most likely that the water detected around the white dwarf GD 61 came from a minor planet at least 90 kilometers (56 miles) in diameterâ ##but potentially much biggerâ##that once orbited the parent star before it became a white dwarf. Like Ceres the water was most likely in the form of ice below the planet s surface. From the amount of rocks and water detected in the outer envelope of the white dwarf the researchers estimate that the disrupted planetary body had a diameter of at least 90 kilometers. However because their observations can only detect what is being accreted in recent history the estimate of its mass is on the conservative side. It is likely that the object was as large as Vesta the largest minor planet in the solar system. In its former life GD 61 was a star somewhat bigger than our Sun and host to a planetary system. About 200 million years ago GD 61 entered its death throes and became a white dwarf yet parts of its planetary system survived. The water-rich minor planet was knocked out of its regular orbit and plunged into a very close orbit where it was shredded by the starâ#gravitational force. Researchers believe that destabilizing the orbit of the minor planet requires a so far unseen much larger planet going around the white dwarf. t this stage in its existence all that remains of this rocky body is simply dust and debris that has been pulled into the orbit of its dying parent starâ#says Boris Gänsicke professor of physics at the University of Warwick. owever this planetary graveyard swirling around the embers of its parent star is a rich source of information about its former life.  In these remnants lie chemical clues which point towards a previous existence as a water-rich terrestrial body. hose two ingredientsâ##a rocky surface and waterâ##are key in the hunt for habitable planets outside our solar system so itâ#very exciting to find them together for the first time outside our solar system.?The finding of water in a large asteroid means the building blocks of habitable planets existedâ ##and maybe still existâ##in the GD 61 system and likely also around substantial number of similar parent starssays lead author Jay Farihi from the Institute of Astronomy at the University of Cambridge. hese water-rich building blocks and the terrestrial planets they build may in fact be commonâ##a system cannot create things as big as asteroids and avoid building planets and GD 61 had the ingredients to deliver lots of water to their surfaces. ur results demonstrate that there was definitely potential for habitable planets in this exoplanetary system . or their analysis the researchers used ultraviolet spectroscopy data obtained with the Cosmic Origins Spectrograph on board the Hubble space telescope of the white dwarf GD 61. As the atmosphere of the Earth blocks the ultraviolet light such study can only be carried out from space. Additional observations were obtained with both of the 10m telescopes of the W. M. Keck Observatory on the summit of Mauna kea Hawaii. The Hubble and Keck data allows the researchers to identify the different chemical elements that are polluting the outer layers white dwarf. Using a sophisticated computer model of the white dwarf atmosphere developed by Detlev Koester at the University of Kiel they were able to infer the chemical composition of the shredded minor planet. To date observations of 12 destroyed exoplanets orbiting white dwarves have been carried out but this is the first time the signature of water has been found. Source: University of Warwickyou are free to share this article under the Creative Commons Attribution-Noderivs 3. 0 Unported license h
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