By James Morgan
Diamond, nature’s hardest material, has been crushed to record extremes of pressure using the “world’s biggest laser”, US scientists report.
The carbon crystal was condensed to the core pressure of Saturn – 14 times that at the centre of the Earth.
The big squeeze was performed inside the US National Ignition Facility, which recently featured in Star Trek.
It gives clues to the conditions deep inside giant, carbon-rich planets, says a study in Nature journal.
“We don’t know what lies within the core of Jupiter or Saturn but now for the first time we now have the ability to study how matter exists under these extreme conditions of pressure and temperature,” said lead author Dr Ray Smith, of Lawrence Livermore National Laboratory, California.
“Our experiments provide a method for recreating conditions within the cores of giant gas planets – both within our solar system and beyond.
“It has been proposed, for example, that Neptune has a diamond in its core, due to decomposition of methane which gets compacted under extreme pressure.
“The Kepler space mission has found Neptune-sized planets to be very common in our galaxy.”
The planets and stars we see in the night sky were formed by powerful gravitational forces that crushed their constituent atoms tightly together.
The extreme pressures in their cores are expected to cause dramatic changes to the properties of matter.
How, on Earth, we can replicate these alien environments is a terrific challenge for scientists.
The US National Ignition Facility (NIF) was built to study inertial confinement nuclear fusion, and features 192 lasers which are used to bombard materials with energy.
Its target chamber famously doubled as the Starship Enterprise’s “warp core” in the movie Star Trek: Into Darkness.
US researchers used NIF to compress carbon via a technique known as “dynamic ramped compression”.
They focused 176 laser beams onto a millimetre-scale target diamond, held at the centre of a 10m aluminium sphere.
“The challenge in our experiments was keeping temperatures low enough to be relevant to gas giant planets like Jupiter,” Dr Smith told BBC News.
“We accomplished this by carefully tuning the rate at which the laser intensity changes with time. The problem is similar to moving a plough slowly enough that sand is being pushed forward without building up in height.”
The combined energy of the lasers (0.76 megaJoules, or MJ) created pressure waves in the diamond, compressing it to five terapascals (50 million atmospheres) – similar to the pressure at the centre of Saturn.