Scientists are trying to determine what happens to matter when it is exposed to the immense pressures at the center of gas giant planets and stars. And to help them figure it out, they have hit a tiny sliver of a diamond with the largest laser system on Earth.
"The goal of the shots is to try and create planetary core conditions on Earth," said Ray Smith, a physicist at Lawrence Livermore National Laboratory. "And by that I mean very high pressure and relatively low temperature."
Up until 15 years ago, it was expected that if you compressed materials to very high pressures they would behave in a manner very easy to understand, Smith explained. The general thinking was that if you imagine atoms as balls, those balls would simply get closer together at very high pressures.
But most scientists don't think that way anymore. Instead, the theoretical consensus is that matter behaves in a much more complicated way at high pressures -- but there haven't been experiments that can back up those theoretical predictions.
But now, for the first time, Smith and his colleagues have been able to simulate here on Earth the pressure you might find at the center of Saturn.
In a new study in Nature, they describe how they slammed a tiny sliver of a diamond with the most powerful laser system in the world, compressing the diamond to the density of lead.
"The initial goal, which we achieved, is to generate conditions that are relative to planetary cores," said Smith, lead author of the paper. "The expectation is that we will get these really weird states of matter."
The diamond sliver that got hit with the laser was tiny -- 3 millimeters by 0.2 of a millimeter. It was attached to the outer wall of a small gold cylinder 1 centimeter tall and half a centimeter wide that in turn was placed in a high-tech spherical vacuum chamber 32 feet in diameter. (Itty-bitty cylinder, great big chamber.)
The entire setup is part of the National Ignition Facility, or NIF, at Livermore, and it is so futuristic-looking it stood in for the Enterprise's warp core in the movie "Star Trek Into Darkness."
The NIF was designed to do nuclear fusion experiments, but for a short amount of time Smith and his team were able to use it to put the highest pressure ever possible into their diamond sample.
Over the course of the experiment, the diamond sliver was exposed to 50 million times Earth's atmospheric pressure. To put that in perspective, the pressure at the deepest parts of our oceans is about 1,000 times atmospheric pressure. If you go to the center of the Earth where our planet's iron core resides, it is 3.6 million times atmospheric pressure.
The exposure didn't last long, however -- just a few nanoseconds.
In this experiment the researchers did not observe any exotic states of matter. "That doesn't mean it didn't take place," said Smith. "It just means we weren't able to measure it."
Ultimately, the scientists hope to generate exotic phases of matter in such a way that they stick around even after the pressure has been removed. That way they can study them and get a better understanding of what goes on in the center of giant planets in our solar system and beyond.
"That would be an ideal thing to happen," said Smith.
In a News and Views article accompanying the study, Chris J. Packard of University College London and Richard Needs in the Theory of Condensed Matter Group in the Cavendish Laboratory in Cambridge, England, say the experiment is exciting but suggest the work of studying matter at extreme pressures has just begun.
"Although the pressures probed in the current experiments are immense, nature is even more ambitious," they write. "The giant exoplanets are a stepping stone to stars where [even greater pressures] are reached."
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