In its hunt for Earth-like worlds, NASA's Kepler telescope, which launched March 6, should tell us something about the planets that occupy sibling solar systems. Some scientists, however, are crossing that frontier without leaving their laboratories.
They have uncovered worlds where helium, normally a transparent gas that can't hold an electric charge, becomes fluid metal that can conduct electricity. They have probed the melting point of diamonds to understand the building blocks of icy planets like Neptune.
The experiments have been largely based on millions of computations, though that is about to change with the debut this year of a new national laboratory that has the power to compress hydrogen down to the density of copper.
"It's an extraordinary time for this type of science," said Gilbert Collins, a physicist with the Lawrence Livermore National Laboratory in California, host to the new National Ignition Facility, which will use the power of 192 infrared lasers to demonstrate nuclear fusion.
Scientists plan to use the laser beams to hit a tiny target, creating conditions momentarily similar to what exists in the cores of stars and giant planets and inside nuclear weapons.
"Most of the planets we know about are outside our own solar system. They're large, they're in planetary systems that are bizarre — except, well actually, it's perhaps our planetary system that stands out as being a little bit bizarre," said planetary scientist Raymond Jeanloz, with the University of California at Berkeley.
Scientists' first look at Mother Nature's planetary toolkit began with Earth, where interior pressures are about 3.5 million times higher than on the surface. They then moved on to Jupiter, the solar system's largest world, with an interior pressure 70 million times stronger than Earth's.
Prodded by discoveries of extra-solar planets up to 10 times larger than Jupiter, physicists are beginning to explore how matter behaves at pressures that are millions or even a billion times greater than on Earth.
"We've had a real breakthrough experimentally in being able to begin to reproduce these kinds of enormous pressures in the laboratory so we can actually study the properties of matter in these conditions," Jeanloz said.
The transformation of helium into liquid metal occurs at 1 million atmospheres, such as what exists in Earth's core, Jeanloz added.
At that pressure, "The chemical bonding between atoms is dramatically altered," he said. "Materials have totally new properties at these conditions."
At 1 billion times atmospheric pressure, it is not just the chemical bonds, but the atoms themselves that are crushed.
"This is a regime of a new kind of chemistry of materials that we're really on the brink of being able to explore," Jeanloz said.
