Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Experients may force revision of astrophysical models of the universe

Ice giant planets have more water volume than formerly estimated, Sandia Labs Z accelerator tests indicate

In a challenge to current astrophysical models of the universe, researchers at Sandia National Laboratories Z machine and the University of Rostock in Germany have found that current estimates of ice-giant planetary interiors overstate water's compressibility by as much as 30 percent.

The work was reported in the paper "Probing the Interior of the Ice Giants" in the Feb. 27 Physical Review Letters.

"Our results question science's understanding of the internal structure of these planets," said Sandia lead author Marcus Knudson, "and should require revisiting essentially all the modeling of ice giants within and outside our solar system."

An accurate estimate of water's shrinking volume under the huge gravitational pressures of large planets is essential to astrophysicists trying to model the evolution of the universe. They need to assume how much space is taken up by water trapped under high density and pressure, deep inside a planet, to calculate how much is needed of other elements to flesh out the planet's astronomical image.

To come up with the composition of the so-called ice-giants Neptune and Uranus, as well as any of the ice-giant exoplanets being discovered in distant star systems, astrophysicists begin with the orbit, age, radius and mass of each planet. Then, using equations that describe the behavior of elements as the forming planet cooled, they calculate what light and heavy elements might have contributed to its evolution to end up with the current celestial object.

But if estimates of water volume are off-target, then so is everything else.

The measurements — 10 times more accurate than any previously reported — at Sandia's Z accelerator agree with results from a modern simulation effort that uses the quantum mechanics of Schrödinger's wave equation — the fundamental equation of wave mechanics — to predict the behavior of water under extreme pressure and density.

The model, developed through a University of Rostock and Sandia collaboration, is called "First Principles Modeling" because it contains no tuning parameters.

"You're solving Schrödinger's equation from a quantum mechanical perspective with hydrogen and oxygen as input; there aren't any knobs for finagling the result you want or expect," Knudson said.

The model's results are quite different from earlier chemical pictures of water's behavior under pressure, but agree quite well with the Z machine's test results, said Knudson. These results were achieved by using Z's magnetic fields to shoot tiny plates 40 times faster than a rifle bullet into a water-sample target a few millimeters away. The impact of each plate into the target created a huge shock wave that compressed the water to roughly one-fourth its original volume, momentarily creating conditions similar to those in the interior of the ice giants.

Sub-nanosecond observations captured the behavior of water under pressures and densities that occur somewhere between the surface and core of ice giants.

"We took advantage of recent, more precise methods to measure the speed of the shock wave moving through the water sample by measuring the Doppler shift of laser light reflected from the moving shock front, to 0.1 percent accuracy," said Knudson.

The re-shocked state of water was also determined by observing its behavior as the shock wave reflected back into the water from a quartz rear window (its characteristics also determined) in the target. These results provided a direct test of the First Principles model along a thermodynamic path that mimics the path one would follow if one could bore deep into a planet's interior.

Multiple experiments were performed, providing a series of results at increasing pressures to create an accurate equation of state. Such equations link changes in pressures with changes in temperatures and volumes.

Z can create more pressure — up to 20 megabars — than at Earth's core (roughly 3.5 megabars), and millions of times Earth's atmospheric pressure. The Z projectiles, called flyer plates, achieve velocities from 12 to 27 kilometers a second, or up to 60,000 mph. The pressure at the center of Neptune is roughly 8 megabars.

Water at Z's ice-giant pressures also was found to have reflectivity like that of a weak metal, raising the possibility that water's charged molecular fragments might be capable of generating a magnetic field. This could help explain certain puzzling aspects of the magnetic fields around Neptune and Uranus.

"Reducing uncertainty on the composition of planetary systems by precisely measuring the equation of state of water at extreme conditions can only help us understand how these systems formed," Knudson said.

These experimental techniques also are used at Z to study materials of critical importance to the nuclear weapons program. In addition to producing the largest amount of X-rays on Earth when firing, the huge pressures generated by Z make it useful to astrophysicists seeking data similar to that produced by black holes and neutron stars.

Also listed as paper authors are Mike Desjarlais, Ray Lemke and Thomas Mattsson from Sandia, and Martin French, Nadine Nettelmann and Ronald Redmer from the University of Rostock's Institute of Physics.

Research support was provided by the German Science Foundation and the National Nuclear Security Administration.

Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies and economic competitiveness.

neal singer | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht X-ray photoelectron spectroscopy under real ambient pressure conditions
28.06.2017 | National Institutes of Natural Sciences

nachricht New photoacoustic technique detects gases at parts-per-quadrillion level
28.06.2017 | Brown University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>



Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

Latest News

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

More VideoLinks >>>