Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

“Van Gogh” simulations give new insight into turbulent stars

18.04.2007
Stunning simulations that give a multi-dimensional glimpse into the interior of stars show that material bubbling around the convection zone induces a rich spectrum of internal gravity waves in the stable layers above and below.

The swirling simulations, which are reminiscent of Van Gogh’s star paintings, show the interior of a star during the Asymptotic Giant Branch (AGB) phase, the final stage of a low- and intermediate-mass star’s life before it becomes a white dwarf. It is during this phase that many of the heavier elements, such as carbon and sodium, are created inside the stars. The core of the star is surrounded by shells of helium and hydrogen, in which nuclear fusion periodically switches off and on in a process called Helium-Shell Flashes, triggering increased bursts of mixing and heating. The models focus on the turbulent convection zone in the helium shell and show how it interacts with the stable, stratified layers above and below.

Dr Falk Herwig said, “Until recently we’ve only had one-dimensional models of the interior. That’s very different from being able to work out in detail and 2 or 3 dimensions what’s going on deep inside and seeing how the different layers interact. The three-dimensional simulation is so complicated that we have been using as much computing time as some of the large cosmological simulations. This is the first time that we’ve been able to see and actually measure the internal gravity waves that are caused by the convective motions in the unstable layer.”

The simulations show that there is minimal penetration of material into adjoining layers from the convection zone but gravitational mode oscillations with a dominating horizontal velocity component, induced at the convective boundaries do cause some of mixing across layers.

Helium-shell flash convection is dominated by large convective cells that are centered in the lower half of the convection zone. The animations show entropy or temperature fluctuations which start off as small bumps at the bottom of the convection zone and expand upwards, developing mushroom-like instabilities that merge into large-scale features. The stable regions above and below are filled with horizontal waves, which are induced almost as soon as the convection plumes start to grow. This means that the gravity waves are not created by the plumes actually hitting the boundaries, but are induced by the build-up of pressure above the plumes.

Anita Heward | alfa
Further information:
http://www.astro.keele.ac.uk/~fherwig/shydro.html

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

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: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>