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To: Gilbert Drapeau who wrote (5423)	4/6/2001 6:14:34 PM
From: CH4	Respond to of 5827

Scientists: Neutron Stars Hold Gold Updated: Thu, Apr 05 05:31 PM EDT By CHRIS FONTAINE, Associated Press Writer LONDON (AP) - There's gold in them thar colliding neutron stars. A team of scientists said Thursday that the origins of most of the gold, platinum and other heavy elements on Earth can be traced to the massive explosions of colliding neutron stars, hundreds of millions of years before the birth of the Solar System. "This is an incredible result," exclaimed senior team member Stephan Rosswog after the scientists' data were released. "It's exciting to think that the gold in wedding rings was formed far away by colliding stars." It has long been accepted that common elements, such as oxygen and carbon, are created when dying stars explode into supernovae, but researchers have been puzzled by data that suggests these stellar explosions do not produce enough heavy elements to account for their abundance on Earth. The scientists - from the University of Leicester, in England, and the University of Basel, in Switzerland - believe rare pairs of neutron stars hold the answer. The report was presented Thursday to the National Astronomy Meeting at Cambridge, England. Neutron stars are the super-dense cores of large stars that survive supernovae. They contain about as much matter as our sun, but are only about the size of a large city. Sometimes two are found orbiting each other - leftovers of a binary star system. Four such pairs are known to exist in our galaxy. The team used a supercomputer at the U.K. Astrophysical Fluids Facility in Leicester, 100 miles north of London, to model what might happen if the intense gravity created by these pairs slowly forced them to spiral closer and collide. One such calculation takes the supercomputer several weeks to get through, but represents just the final few milliseconds in the lives of the two stars. It shows that as the neutron stars get closer, immense forces tear them apart, releasing enough energy to outshine the entire universe for a few milliseconds, the team said. Team member Melvin Davis of Leicester said the explosion most likely creates a black hole - a light-sucking tear in space - and ejects ash so hot that nuclear reactions take place as it races outward, mashing newly created protons into the nuclei of lighter elements to create heavy elements. The ejected material eventually mixes with the gas and dust between stars that, in turn, collapses down to form new generations of stars, slowly spreading heavy metals throughout the galaxy. The proportion of matter created in these infrequent cataclysms over the 10-billion-year life of the universe closely matches the spectrum of elements found in our 5-billion-year-old Solar System, the team said, providing strong evidence that the theory is solid. "The thing that is really quite compelling is that our models really do reproduce the relevant amounts of elements in the universe very, very accurately," Davis said after the release of their report. "It answers part of the question, `Where did all this stuff come from?"' Stan Woosley, professor of astrophysics at the University of California-Santa Cruz, called the data compelling, but said it lacked a conclusive description of the so-called R-process - one of two ways that heavy elements can be formed. The other - the S-process - is better understood: Heavy elements are created as a star burns its hydrogen into helium, but the variety and amounts produced are limited. Some astrophysicist believe the R-process also occurs in a supernova, but scientists' understanding of supernovae is limited and computer models that could prove the theory don't exist. Supporters of the supernova theory argue that collapses of binary neutron stars happen too infrequently. If large amounts of heavy elements are created in the more common supernovae, it would explain this uniformity. "It's a nice development and a nice calculation," said Woosley, speaking to The Associated Press by phone from California, "but not everyone is going to accept that this is how the R-process is made." --- On the Net: Royal Astronomical Society, ras.org.uk Video images, ukaff.ac.uk