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Smooshed diamonds: A window into exoplanets?

Even diamonds can be compressed, creating extreme materials — like nothing else on Earth

By
8:30am, July 22, 2014

The gold cylinder converts the laser’s blue light into X-rays. They create pressure on the diamond sample, mounted to the side of the gold cylinder and at the very end of the cone. (That cone shields the target from stray energy).

Matt Swisher

Researchers have squeezed diamonds to a record-setting pressure — 14 times as high as that inside Earth’s core. This super-compressed carbon could reveal the type of extreme conditions present deep inside supersized exoplanets, those out beyond the solar system. That’s what scientists report in the July 17 Nature.

Diamond is a crystal made from carbon. It also is the least compressible material known. But that didn’t daunt physicist Ray Smith of Lawrence Livermore National Laboratory, in California, and his team. They harnessed the world’s largest laser. At the National Ignition Facility, in Livermore, Calif., it’s the powerful device designed for laser-fusion research.

Smith’s team focused 176 laser beams onto hair-thin layers of gold and artificial diamond (see setup in photo above). This created waves of pressure. The gold layers helped disperse heat, Smith says. This helped avoid a problem that can mean diamonds aren’t forever: As pressure mounts, diamond can liquefy, he notes. And that would have ruined the experiment. But his team found that an initial small wave of pressure helps prevent that melting before the researchers gradually and massively ramped up the material’s compression. How massively? To 5 terapascals, which is about 50 million times Earth’s atmospheric pressure at sea level.

The entire process lasted a mere 20 billionths of a second!

Smith says the properties of carbon under pressure could help researchers better simulate the insides of Neptune-like gassy exoplanets. Some, he notes, may have diamond cores. To mimic the cores of giant rocky planets, he plans to compress iron by exerting similar pressures.

Power Words

carbon  The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

core  In geology, Earth’s innermost layer.

density     A measure of the consistency of an object, found by dividing the mass by the volume.

diamond One of the hardest known substances and rarest gems on Earth. Diamonds form deep within the planet when carbon is compressed under incredibly strong pressure.

exoplanet     A planet that orbits a star outside the solar system.

Neptune  The furthest planet from the sun in our solar system and its fourth largest.

nuclear fusion    The process of forcing together the nuclei of atoms.

pascal     A unit of pressure in the metric system. It is named for Blaise Pascal, the 17th century French scientist and mathematician. He also developed what became known as Pascal’s law of pressure. It holds that when a confined liquid is pressed, that pressure will be transmitted throughout the liquid in all directions, without any losses.

physics     The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. It’s an alternative to quantum physics in explaining the motions and behavior of matter. A scientist who works in that field is known as a physicist.

planet    A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and it must have cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, it must be big enough to pull neighboring objects into the planet itself or to sling-shot them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now consists of eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

solar system  The eight major planets and their moons in orbit around the sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.

simulate  To deceive in some way by imitating the form or function of something. A simulated dietary fat, for instance, may deceive the mouth that it has tasted a real fat because it has the same feel on the tongue — without having any calories. A simulated sense of touch may fool the brain into thinking a finger has touched something even though a hand may no longer exists and has been replaced by a synthetic limb. (in computing) To try and imitate the conditions, functions or appearance of something. Computer programs that do this are referred to as simulations.

tera       A prefix for units of measurement meaning trillion in the international metric system. 

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