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Science / Medicine : A Weekly Roundup of News, Features and Commentary : Silicon Grains Pre-Date All

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Scientists have found in a meteorite grains of a silicon compound that, along with previously discovered diamonds, are the oldest particles yet known to man.

Researchers at the University of Chicago and Washington University said they isolated grains of silicon carbide from before and beyond the Earth’s solar system that are at least 4.5 billion years old.

They said the discovery has “great potential value” for helping understand the life cycle of stars and the creation of the Earth’s solar system.

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Silicon carbide is not found naturally on Earth but is manufactured and widely used as an abrasive and electrical resistor. The researchers said, in a paper published in Nature, that astronomers have detected signs of the substance around distant stars but that this marked the first time naturally occurring silicon carbide has been directly identified and measured in a laboratory.

The substance was probably formed in several carbon-rich stars and scattered into space when the stars ejected their outer layers at least 4.5 billion years ago, before our own solar system was formed. The exact age of the particles beyond that is impossible to estimate, the report said.

The dust was compacted into larger bodies over the eons which later broke apart in collisions or explosions to form meteorites. The compound survived because it is so hard.

In March the same scientists found in a different meteorite diamonds so small that trillions could fit on the head of a pin. The diamond dust had a similar origin, formed in the atmosphere of a dying star and strewn across space where it became part of larger bodies that were eventually broken up into meteorites. Both substances, he said, are the oldest material yet found.

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