Grains of sand from ancient supernova found in meteorites
Apr 19, 2013 by Diana Lutz
…………The first silica grains are discovered
In 2009 Christine Floss, PhD, research professor of physics at Washington University in St. Louis, and Frank Stadermann, PhD, since deceased, found the first silica grain in a meteorite. Their find was followed within the next few years by the discovery of four more grains.
All of these grains were enriched in oxygen-17 relative to solar. "This meant they had probably come from red giant or AGB stars" Floss said.
When Haenecour began his graduate study with Floss, she had him look at a primitive meteorite that had been picked up in Antarctica by a U.S. team. Antarctica is prime meteorite-hunting-territory because the dark rocks show up clearly against the white snow and ice.
Haenecour found 138 presolar grains in the meteorite slice he examined and to his delight one of them was a silica grain, But this one was enriched in oxygen-18, which meant it came from a core-collapse supernova, not a red giant.
He knew that another graduate student in the lab had found a silica grain rich in oxygen-18. Xuchao Zhao, now a scientist at the Institute of Geology and Geophysics in Beijing, China, found his grain in a meteorite picked up in Antarctica by the Chinese Antarctic Research Expedition.
A massive star that will explode at the end of its life, a core-collapse supernova has a layered structure rather like that of an onion. Credit: Wikipedia
With two specks to go on, Haenecour tackled the difficult problem of calculating how a supernova might have produced silica grains. Before it explodes, a supernova is a giant onion, made up of concentric layers dominated by different elements.
Some theoretical models predicted that silica might be produced in massive oxygen-rich layers near the core of the supernova. But if silica grains could condense there, Haenecour and his colleagues thought, they should be enriched in oxygen-16, not oxygen-18.
They found they could reproduce the oxygen-18 enrichment of the two grains by mixing small amounts of material from the oxygen-rich inner zones and the oxygen-18-rich helium/carbon zone with large amounts of material from the hydrogen envelope of the supernova.
In fact, Haenecour said, the mixing needed to produce the composition of the two grains was so similar that the grains might well come from the same supernova. Could it have been the supernova whose explosion is thought to have kick-started the collapse of the molecular cloud out of which the planets of the solar system formed?
How strange to think that two tiny grains of sand could be the humble bearers of such momentous tidings from so long ago and so far away.
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•1 / 5 (1)Apr 23, 2013it is true that our solar system is also a result of supernova explosion but at the time of explosion heavy metal comes out 1st & nearest planet formed 1st. supernova remnant & radiation from galactic core are the raw materials for all ...