10-22-2011, 02:10 PM
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Huge Disc Of Ice In Space
| |The Herschel Space Observatory has captured for the first time a huge 'disc' of icy vapour clustered round a young star as it develops into a solar system.
The water round the star stretches far out into the 'edge' of its system. The water is likely to form into icy comets, which would crash into young worlds, bringing oceans with them.
The find suggests that water-covered planets such as Earth may be common.
This artists impression shows a disc of cold water vapour stretching across the young solar system from the interior where the sun warms it to an outer region where icy comets form:
‘Our observations of this cold vapor indicate enough water exists in the disk to fill thousands of Earth oceans,’ said astronomer Michiel Hogerheijde of Leiden Observatory in The Netherlands. Hogerheijde is the lead author of a paper in the journal Science.
Previous watery discs round stars were smaller and closer in - and don't stretch out to the regions where comets form.
The freezing, watery haze detected by Hogerheijde and his team is thought to originate from ice-coated grains of dust near the disc surface.
Ultraviolet light from the star causes some water molecules to break free of this ice, creating a thin layer of gas with a light signature detected by Herschel’s Heterodyne Instrument for the Far-Infrared, - known as Hifi. It's an incredibly weak signal and tests the instrument to its limits.
A spike in the wavelengths of light detected from the system allowed astronomers to deduce the presence of a large, cold disc of water surrounding the young star:
‘These are the most sensitive HIFI observations to date,’ said Paul Goldsmith, NASA project scientist for the Herschel Space Observatory at the agency’s Jet Propulsion Laboratory in Pasadena, Calif. ‘It is a testament to the instrument builders that such weak signals can be detected.’
TW Hydrae, the star, is 10 million years old and located about 175 light-years away from Earth, in the constellation Hydra.
The giant disk of material that encircles the star has a size nearly 200 times the distance between Earth and the Sun.
Over the next few million years, astronomers believe matter within the disk will collide and grow into planets, asteroids and other cosmic bodies.
Dust and ice particles will coalesce into icy comets.
As the new solar system evolves, icy comets are likely to deposit much of the water they contain on freshly created worlds through impacts, giving rise to oceans.
Astronomers believe TW Hydrae and its icy disk may be representative of many other young star systems, providing new insights on how water-rich planets could form throughout the universe.