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Planetary Physics

Since 1995, astronomers have discovered hundreds of new planets outside our Solar System, some smaller than Earth and others a dozen times more massive than Jupiter. Most of the "extrasolar" planets discovered to date are giant or super-giant planets with interior conditions reaching pressures and temperatures as high as about one gigabar (one billion times Earth's atmospheric pressure) and 10,000 kelvins (17,540 degrees Fahrenheit). Materials are known to undergo fundamental changes in their physical and chemical-bonding properties at a fraction of such pressures, so there is considerable interest among scientists in experimentally observing materials at extreme conditions to better understand the makeup and geophysical evolution of these bodies—the platforms on which life has developed.

Possible Interior of Jupiter Possible interior of Jupiter.

A number of questions relevant to understanding the interiors of large planets require experimental investigation to answer, including:

  • At pressures above 10 Mbar (ten million times Earth's atmosphere) and temperatures below 1,000 kelvins, what is the nature of a solid? For hydrogen at these conditions, does it form a special kind of structure known as a Wigner crystal, does it become superfluid, or does it become a superconductor?
  • At somewhat higher temperatures, might there be a plasma phase transition in hydrogen from a dense, insulating phase to a highly ionized phase? (A phase transition occurs when, for example, ice transforms into water, or one form of crystal changes to another.)
  • How do mixtures of hydrogen and helium behave at extreme densities, and might there be a phase separation between them?
  • Under these temperature and pressure conditions, might a special form of nuclear reactions (so-called pycnonuclear reactions) occur?

Studying high pressure, moderate temperature states of condensed matter at the National Ignition Facility will enable scientists to simulate the deep core conditions of large planets and answer some of the most fundamental questions in planetary physics.

More Information

Basic Research Directions for User Science at the National Ignition Facility, National Nuclear Security Administration and U.S. Department of Energy Office of Science, November 2011

"A Laser Look Inside Planets," Science & Technology Review, June 2009

"A Laboratory to Probe a Planet's Deep Interior," Science & Technology Review, July/August 2007

"Achieving high-density states through shock-wave loading of precompressed samples," Proceedings of the National Academy of Sciences, May 4, 2007 (PDF)

"New Routes to High Temperatures and Pressures," Science & Technology Review, March 2007

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