When stars use up all hydrogen fuel and die, they won't go without a bang. In fact, when massive stars collapse, they explode around 10 to 100 times brighter than the average supernova. The exact mechanism has not been well understood until a team of researchers and astrophysicists demonstrated the collapse of massive stars using a simulation in a supercomputer.
Researchers from California Institute of Technology, University of California Berkeley, Albert Einstein Institute and the Perimeter Institute for Theoretical Physics used the National Science Foundation's Blue Waters supercomputer to show a three-dimensional simulation on how massive stars die and collapse.
The 10-millisecond supercomputer simulation of the collapse of a massive star into a neutron star — often called hypernova — showed that the star can create an enormous magnetic field. As it collapses, the star will be in a rapid rotation, forming a dynamo that revs the magnetic field million billion times stronger than Earth's own magnetic field.
This strong field is adequate enough to focus and accelerate gas along the rotation axis of the star. Thus, two jets can create blasts of highly energetic gamma rays.
"We were looking for the basic mechanism, the core engine, behind how a collapsing star could lead to the formation of jets," said Erik Schnetter, computational scientist at Perimeter Institute. He designed the computer programs for the simulation used in the study.
Magnetic fields appear in many stars and when these stars are able to rotate sufficiently and rapidly, large-scale dynamos will be present. Dubbed stellar dynamos, they generate electrical currents as the stars' magnetic fields travel through space.
"A dynamo is a way of taking the small-scale magnetic structures inside a massive star and converting them into larger and larger magnetic structures needed to produce hypernovae and long gamma-ray bursts. That kicks off the process," said Philipp Mösta, the study's first author from the University of California Berkeley, adding that the study allowed them to prove the process could actually work out, as was previously believed.
The researchers further explained that the formation of galaxies, stars and life itself are connected to energy and matter blasted from exploding starts. In fact, the sun which supports life on Earth is widely known to come from an earlier supernova. So, deepening our understanding of how these cosmic events happen is important.
The study was published in the journal Nature on Nov. 30.
