Scientists have bombarded hydrogen with 168 powerful laser beams – part of the world’s largest laser, the National Ignition Facility at Lawrence Livermore National Laboratory – to reproduce what happens to the gas under the intense pressures at the cores of giant planets.
What they saw confirms predictions that if you keep hydrogen cool enough while pounding on it with six million times atmospheric pressure – twice the pressure at the center of the Earth – the hydrogen turns into a shiny metal.
“It’s like squeezing air and turning it into a shiny, light version of liquid mercury. Although exotic at Earth’s surface, metallic hydrogen is the main material inside most giant planets and stars,” said Raymond Jeanloz, a UC Berkeley professor of astronomy and of earth and planetary science and a co-author of the research.
The team’s optical measurements of the so-called insulator-to-metal transition in fluid hydrogen resolved discrepancies in previous experiments and established new benchmarks for calculations used to construct planetary models. Livermore Lab physicist Peter Celliers was the lead author of the paper, which was published this week in the journal Science.
“These results are a true experimental tour de force and are particularly important because they provide a very stringent test on the different varieties of numerical simulations that one can use to predict the properties of planetary constituents at high pressure — necessary to model the internal structure and evolutionary processes of Jupiter and Saturn,” said Marius Millot, a physicist at LLNL and co-author of the paper.