Diamonds Rain Down on Earth From Exploding Stars
The universe is awash with tiny diamonds that sometimes rain down on the Earth in meteorites, bringing evidence from deep space that may be of profound importance in understanding the evolution of the universe, scientists have discovered.
The diamonds, so small that trillions could rest on the head of a pin, were formed in the violent explosions of dying stars long ago and may be the oldest particles ever discovered, according to today’s issue of Nature, the British science journal, which describes the discovery as “astounding.”
The diamonds should contain traces of every element created by exploding stars known as supernovae, which are believed to be the source of the heavy elements that form new stars and even led to life on Earth, Roy Lewis, a physicist with the University of Chicago and a co-author of the report, said in a telephone interview.
Thus the diamonds are messengers from deep space encoded with the history of the evolution of stars, he said. “This is a sample return mission that goes beyond the wildest dreams of NASA.”
When the solar system was formed 4.5 billion years ago out of clouds of interstellar gas and dust, most of the original ingredients were melted or vaporized, losing their chemical identities, Lewis said. The diamonds, however, were strong enough to have endured that process, and many of them were trapped in the matrix that was then coalescing into such things as meteorites.
Closest Exploding Star
The announcement comes on the heels of the discovery three weeks ago of a supernova that is the closest exploding star observed in nearly 400 years.
Lewis and Edward Anders, also of the University of Chicago, discovered the diamonds by accident while studying a rare xenon gas that was carried in small grains of carbon in primitive meteorites. The gas had intrigued them because its composition was such that it could not have been formed in the solar system.
They discovered the diamonds while continuing the work of John Wacker, who had left Chicago for a position with the Scripps Institution of Oceanography in San Diego. Wacker had found “something unusual” when he examined the waste materials left behind after dissolving a meteorite in order to study its gases, Lewis said. The residue looked like ordinary white carbon, but the Chicago team later determined that it consisted of trillions and trillions of minute diamonds.
The researchers examined three other meteorites known to contain the unusual xenon, and they found diamonds in those as well.
The work suggests, according to Anders, that “the formation of diamonds occurs on an enormous scale in the universe.”
When the Chicago team analyzed the diamonds, they found they contained xenon that could only have been “presolar” because it is twice as rich in certain isotopes as xenon found in the solar system.
Thus the gas must have been formed, along with the diamonds that acted as its “container,” in the upper atmosphere of a dying star where temperatures and abundant hydrogen could encourage diamonds to form as carbon gas condensed, Lewis said.
Carried by Shock Wave
When the star subsequently exploded as a supernova, the diamonds were blasted into space and carried across the universe by the kind of shock wave that many astronomers believe is responsible for pushing materials together, thus forming stars and galaxies.
“In the lab,” Lewis said, “these little diamonds tend to stick together, so we end up with clumps of billions and billions of diamonds that make up little specks” in the bottom of the canister.
“So we have millions of specks that contain billions of diamonds,” he said. “We end up with little piles of material that we can weigh and load into our mass spectrometers” to determine chemical composition.
The discovery is so new that that process has just begun, but the Chicago team believes that the “little piles” of diamonds should contain samples of not just xenon but every material present when the supernova occurred.
Industry Implications
Although the diamonds are too small to have any commercial value, the discovery may have significant implications for industry.
Diamonds normally form only when carbon is subjected to extreme pressures, such as those found deep in the Earth’s crust. Small diamonds have been found in the past in meteorites; they were formed by the heat generated when the meteorite struck the Earth and are known as “shock” diamonds, and they have little commercial value.
Recent research in Japan and the Soviet Union shows, however, that diamonds can also form at low pressures from hot gases containing carbon. The Chicago discovery shows that nature also forms diamonds at low pressures, and a better understanding of that process could lead to improved methods for manufacturing diamonds for industrial purposes, the scientists said.
