By determining the properties of hydrogen-helium mixtures at the millions of atmospheres of pressure present in the interior of Saturn and Jupiter, physicists at Lawrence Livermore National Laboratory and the University of Illinois at Urbana-Champaign have determined the temperature at a given pressure when helium becomes insoluble in dense metallic hydrogen. The results are directly relevant to models of the interior structure and evolution of Jovian planets.
Hydrogen and helium are the two lightest and most common elements in the universe. Because of their ubiquitous nature, they are critical in cosmological nucleosynthesis and are essential elements of stars and giant planets. Hydrogen by itself in the observable universe provides clues to the origin and large-scale structures of galaxies.
However, scientists have struggled to determine what conditions are needed for the two elements to mix.
Using first-principle molecular dynamics simulations, Miguel Morales, a DOE Stewardship Science graduate fellow from David Ceperley's group at the University of Illinois worked with LLNL's Eric Schwegler, Sebastien Hamel, Kyle Caspersen and Carlo Pierleoni from the University of L'Aquila in Italy to determine the equation of state of the hydrogen-helium system at extremely high temperatures (4,000-10,000 degrees Kelvin), similar to what would be found in the interior of Saturn and Jupiter.
The team used LLNL's extensive high-performance computing facilities to conduct simulations over a wide range of density, temperature and composition to locate the equation of state of the two elements.
"Our simulation results are consistent with the idea that a large portion of the interior of Saturn has conditions such that hydrogen and helium phase separate," Morales said. "This can account for the apparent discrepancy between the current evolutionary models for Saturn and observational data."
In addition to being made mostly of hydrogen and helium, a characteristic of Jovian planets is that they radiate more energy than they take in from the sun. Various models of their evolution and structure have been developed to describe a relation between the age, volume and mass of the planet and its luminosity.
While this model works for Jupiter by modeling the energy radiation left over from its formation 4.55 billion years ago, it doesn't exactly work for Saturn. Instead, the model seriously underestimates the current luminosity of Saturn.
So the researchers decided to try something different. They determined where helium and hydrogen mix as well as at what temperature they don't mix.
It turned out the temperature where the two elements don't mix is high enough that helium is "partially mixable over a significant fraction of the interior of the Jovian planets with the corresponding region of Saturn being larger than in Jupiter," Schwegler said. "This, in fact, could change the current interior models of Saturn and Jupiter."
The new findings appear in the Jan. 26 online edition of the journal, Proceedings of the National Academy of Sciences.
Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.
Anne Stark | EurekAlert!
Further reports about: > Helium > Hydrogen > Illinois River Watershed > Jupiter > Laboratory > Saturn > cosmological nucleosynthesis > giant planet > giant planets > hydrogen-helium system > jovian planets > metallic hydrogen > molecular dynamics simulations > structures of galaxies > ubiquitous nature
Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences
The universe up close
15.01.2018 | Georg-August-Universität Göttingen
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
16.01.2018 | Materials Sciences
16.01.2018 | Materials Sciences
16.01.2018 | Power and Electrical Engineering