The Point.fr – Published on 13/10/2013 at 16:34 – Edited on 13/10/2013 at 16:46
This finding suggests that, for the first time, the remains of a large asteroid rich in water in another star system.
© Mark A. Garlick / AFP
Never before had all detected outside our solar system water and a rocky body, the “two key elements” for a planet is habitable, emphasize the researchers in a European study published Thursday in the journal Science .
Earlier observations of 12 exoplanets whose remains were destroyed in orbit around white dwarfs, stars at the end of life who have exhausted their nuclear fuel, did not show the presence water.
In the study published Thursday, the remnants of an asteroid that had to be at least 90 km in diameter, are in orbit probably other planets orbiting a dwarf White called GD 61 located approximately 170 light-years from Earth, or 9460 billion kilometers.
magnesium, silicon, iron …
“At this stage of its existence, all that remains of the rocky body is dust and debris around the dying star,” commented Professor Boris Gänsicke, Department of physics from the University of Warwick, UK, one of the main sponsors of the study. “But this global cemetery is a rich source of information,” he says: “These remains contain chemical evidence revealing the existence of this ancient water-rich rocky asteroid.”
These astrophysicists also detected in the debris of magnesium, silicon, iron and oxygen, which are the key ingredients of rocks.
The rocky planets like Earth formed by the aggregation of asteroids and “the fact of finding so much water in such a celestial body size means that the materials forming habitable planets and such planets themselves have existed or still exist in the GD 61 and probably in many other similar systems “star system, reports Jay Farihi, an astrophysicist at the Institute of Astronomy at Cambridge, lead author this discovery.
A dwarf planet composed of 26% water
The asteroid was perhaps a dwarf planet was formed to 26% water, a proportion similar to Ceres in our solar system. By comparison, the Earth is very dry, since water is only 0.02% of its mass. As Ceres, water should be in the form of ice under the surface of the asteroid.
In its previous life, GD 61 was a little larger than our Sun, which in several billion years suffer the same fate star. According to the astronomers, GD 61 has finally exhausted its fuel there 200 million years to become a white dwarf. Part of its planetary system survived, but not asteroids and dwarf planets, which orbit is strongly close to the dying star, where they were destroyed by its gravitational force.
For this research, the scientists relied primarily on observations from a spectrograph on board the Hubble Space Telescope using the ultraviolet rays that can be made from the ground saw the Earth’s atmosphere blocks the radiation.