Scientists model physics of stellar burning
University of California scientist at Los Alamos National Laboratory working with astronomers from around the world recently validated a computer model that predicts the rebirth and stellar burning and mixing processes of evolved stars. The discovery is a leap forward in our understanding of how stars like the sun evolve through violent outbursts during their evolution.
In research published recently in the journal Science, Laboratory astrophysicist Falk Herwig and his colleagues describe how Herwig’s computer model was recently corroborated by radio telescope observations made at the Very Large Array (VLA) in Socorro, N.M. The radio signals collected by the VLA indicate that a star in the constellation Sagittarius known as V4334 Sgr, or Sakurais Object, is about to re-illuminate it’s planetary nebula for the second time, initiating a new phase in the spectacular evolution of this enigmatic star. This never before seen event is another step in a complex chain of events initially triggered by a nuclear burst after the star had already become a hot white dwarf.
Computer simulations of the stellar outburst made nearly 10 years ago by Herwig and others had predicted this series of physics events that would lead up to the rejuvenated planetary nebula. However, V4334 Sgr failed to follow the script as events moved many times more quickly than the simulations predicted. In 2001, Herwig proposed a new fast-evolving model, claiming the problem may be the way in which nuclear burning and rapid mixing was simulated.
Stars typically evolve into white dwarfs and die when they have used up most of their hydrogen, but about a quarter of them, like V4334 Sgr, experience a brief rebirth when their helium suddenly ignites, and the remaining hydrogen in the outer regions is drawn into the helium shell through rapid mixing, causing a massive nuclear explosion. This burst of energy will expand the dying star to gigantic proportions and lower surface temperatures and, in the process, expel prodigious amounts of carbon. V4334 Sgr has just evolved through this phase.
Herwig’s new model predicts that V4334 Sgr will now become much hotter very rapidly and will then slowly repeat the stellar rebirth cycle once more, returning to its current cooler temperature in roughly two hundred years. Only then follows the final episode of reheating for a third time before V4334 Sgr eventually will become an inactive cooling white dwarf.
In addition to Herwig, who works in the Laboratorys Theoretical Division, the stellar burning team included Marcin Hajduk of the University of Manchester and Centrum Astronomii UMK; Peter A.M. van Hoof of Queens University in Belfast and the Royal Observatory of Belgium; Florian Kerber of the European Southern Observatory in Germany; Stefan Kimeswenger of the University of Innsbruck, Austria; Don Pollacco of Queens University in Belfast; Aneurin Evans of Keele University in Staffordshire, UK; Jose Lopez of the National Autonomous University of Mexico in Ensenada; Myfanwy Bryce of Jodrell Bank Observatory in the UK; Stewart P.S. Eyres of the University of Central Lancashire in the UK; and Albert Zijlstra and Mikako Matsuura of the University of Manchester.
Los Alamos National Laboratory is operated by the University of California for the National Nuclear Security Administration of the U.S. Department of Energy and works in partnership with NNSAs Sandia and Lawrence Livermore national laboratories to support NNSA in its mission.
Los Alamos enhances global security by ensuring the safety and reliability of the U.S. nuclear deterrent, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to defense, energy, environment, infrastructure, health and national security concerns.
Todd Hanson | EurekAlert!
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
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...
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...
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...
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...
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)...