Dusty Discs Girdle Distant Solar Systems

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<b>Dusty Discs Girdle Distant Solar Systems</b><br /><br />LINK<br /><br />Cold, dusty discs of debris have been clearly detected around stars in other planet-harbouring solar systems for the first time by NASA's Spitzer Space Telescope. The finding confirms standard theories of planet formation but raises questions about why the discs were found around some stars and not others.<br /><br />The heavenly bodies of our solar system are thought to have begun as a disc of gas and dust about four billion years ago. As the planets and other large bodies gradually coalesced, they swept up dust along their orbits, clearing a space around the Sun. The Sun also thinned out the original disc by sucking in dust or blowing it into space on the solar wind. <br /><br />But then a new type of disc began to take shape as large objects occasionally smashed into each other and kicked up new clouds of dust. This "debris disc" is thought to be fed by collisions in the Kuiper Belt, a band of icy bodies beyond the orbit of Neptune.<br /><br />Such debris discs had been seen around a number of stars, but none of these stars were observed to have planets. Now, a team led by Charles Beichman at NASA's Jet Propulsion Laboratory in Pasadena, California, has used Spitzer to search for the faint infrared glow of dust around 26 stars already known to host planets.<br /><br /><br />Matching belts <br /><br /><br />The researchers found discs around six stars of comparable age to the Sun. They concluded that planets had hollowed out the central part of each disc. This is because the remaining dust was observed, on average, to be at the chilly temperature of just -220°C. This indicates that the inner edge of the dust ring probably lies at a distance similar to that of the Kuiper Belt.<br /><br />"Prior to these observations, we really didn't know of any systems that harboured both planets and discs other than our own solar system," Al