June 3, 2016

Scientists create 3D models of supernovas

At the conclusion of their life, immense stars blow up and spread their composite elements of carbon, iron, and many other natural elements across space. These elements eventually create new stars, solar systems and anything else in the universe, including us.

In a new report published by The Astrophysical Journal, researchers have developed a 3-D digital model that shows the final moments of a star’s life in vibrant detail.

"If we want to understand the chemical evolution of the entire universe and how the stuff that we're made of was processed and distributed throughout the universe, we have to understand the supernova mechanism," Sean Couch, assistant professor of physics and astronomy at Michigan State University, said in a news release.

Over millions of years of nuclear fusion, stars burn heavier and heavier elements. Eventually, these giant stars run out of fuel and acquire an iron core. Unable to support themselves in opposition to their own massive gravitational pull, these stars fail. However, an unknown process turns around the collapse and leads to the star exploding.

"What theorists like me are trying to understand is that in-between step," Couch said. "How do we go from this collapsing iron core to an explosion?"

3D model of a supernova

(Image credit: Sean M. Couch, Michigan State University)

Creating a 3D supernova model

To learn about this step, the study team began developing a 3-D simulation strategy. While this 3-D technique is still in its beginnings, initial results have been encouraging. In 2015, the team published a paper describing 3-D simulations of the final three minutes of iron core growth in a giant star. They discovered that better representations of the star's framework and the motion produced by violent convection play a considerable part at the point of collapse.

"Not surprisingly, we're showing that more realistic initial conditions have a significant impact on the results," Couch said.

Recent developments in computer science allowed the team to make major strides toward more precise supernova simulations by using the 3-D modeling approach. Specifically, the rise of petascale supercomputers made it possible to make high-fidelity models of rotation, magnetic fields and other complicated physics operations that were not achievable previously.

"Generally when we've done these kinds of simulations in the past, we've ignored the fact that magnetic fields exist in the universe because when you add them into a calculation, it increases the complexity by about a factor of two," Couch said. "But with our (new simulations), we're finding that magnetic fields can add a little extra kick at just the right time to help push the supernova toward explosion."

"Our simulations are only a first step toward truly realistic 3-D simulations of supernova," he continued. "But they are already providing a proof-of-principle that the final minutes of a massive star evolution can and should be simulated in 3-D."


Image credit: Sean Couch, Michigan State