Simulations reveal unprecedented details of a star’s evolutionary phase

An international team of researchers have used DiRAC to study a “nuclear burning phase” of a star’s evolution in unprecedented levels of detail and realism.

Most of our understanding of stars and their life cycles come from one-dimensional models, which are severely limited in the amount of detail they can provide. The complex processes inside stars also mean there are many uncertainties which can make these simulations unreliable.

The computational power of DiRAC’s COSMA8 machine at Durham has for the first time enabled a 3D simulation of an entire phase in the life of a 20 solar mass star. Working in three dimensions faithfully captures processes such as convection, and the energy transfer from the star’s convective regions to the surrounding regions where the transfer is radiative. The simulation follows a portion of the star from the early development of the neon-burning phase, fuelling the star’s energy production via fusion to different nuclei such as oxygen, silicon and magnesium, through to its complete exhaustion after a matter of hours or days. The findings, published in the Monthly Notices of the Astronomical Society, provide crucial answers to long-debated questions in stellar physics.

Lead author Federico Rizzuti, a PhD student from Keele University, said:

“For this new publication, we have run 3D simulations of stellar interiors for long enough to see the evolution of one entire ‘nuclear burning phase’, allowing us to study in detail how a nuclear burning phase develops and eventually dies, particularly the complex interaction between nuclear reactions and turbulence in the stellar layers, with a new degree of precision and realism.

“We have found that the nuclear reactions are really efficient during this phase, and soon they consume all the fuel, halting also the movement of elements across the star’s different layers. We were also able to study which chemical elements were consumed and produced during this phase.
“This will give us new information on how stars live and die, and whether they produce supernova explosions, neutron stars and black holes when they die. Our work demonstrates it is finally possible to simulate long portions of a star’s life with 3D models, and we are sure that soon we will see more: this is why we call it the ‘dawn of 3D stellar evolution’ “

The research was supported by the Science & Technology Facilities Council (STFC), ChETEC COST Action (CA16117) and the EU Horizon 2020 programme.

Link to full research