Breakthrough simulations shed light on the lightest neutron star mystery
Scientists have taken a major leap forward in understanding the formation of neutron stars, thanks to new 3D supernova simulations conducted by a team of astrophysicists.
A very light neutron star, made by the explosion of a 9.9 solar mass star, is still surrounded by neutrino-heated material ejected from its hot surface region. The structure shown in the figure is about 250km in diameter. Credit: Associate Professor Bernhard Müller
Led by Associate Professor Bernhard Müller and Professor Alexander Heger from the Monash University, School of Physics and Astronomy the research has provided new insights into the minimum mass of neutron stars formed during supernova explosions. The study is published today in Physical Review Letters.
The work addresses a long-standing question in astrophysics: can current supernova models account for the existence of the lightest neutron star, weighing just 1.174 times the mass of the Sun, in the binary system J0453+1559? The answer is now closer than ever, as their simulations successfully produced a neutron star with a record-low gravitational mass of 1.192 solar masses.
“Our findings push the boundaries of what we know about neutron star formation,” said Associate Professor Müller. “This is the lowest neutron star mass ever obtained in 3D simulations with realistic neutrino transport, and it brings us closer to solving the puzzle posed by these lightweight neutron stars.”
Neutron stars are the ultra-dense remnants of supernova explosions, with their masses determined by the dynamics of the collapsing star and the subsequent explosion.
Previously, models struggled to explain how such low-mass neutron stars could form. Using advanced simulations of stars close to the threshold for iron-core collapse, the research team which also included Dr Jade Powell from the Centre for Astrophysics and Supercomputing at Swinburne University, demonstrated that these lighter remnants are not only possible but may challenge existing assumptions about stellar evolution and explosion physics.
The results also revealed intriguing details about the birth properties of neutron stars. For example, the simulations showed that these stars could receive substantial "kicks" of up to 100 kilometres per second during formation, explaining their movement within binary systems like J0453+1559.
“This discovery shows the importance of high-resolution 3D modelling,” Associate Professor Müller said. “Without this level of detail, we couldn’t capture the complex interplay of forces driving these explosions and shaping their remnants.”
Despite these successes, the team acknowledges there is still a slight gap between their results and the observed mass of the lightest neutron star candidate. Associate Professor Müller noted that minor refinements in pre-collapse models or further exploration of progenitor structures could bridge this discrepancy.
“Our simulations have opened a new chapter in understanding low-mass neutron stars,” said Professor Heger. “While there’s more work to be done, this progress highlights the exciting potential of computational astrophysics to test and refine our theories of the universe.”
This research not only advances our knowledge of neutron stars but also has broader implications for nuclear physics and our understanding of the cosmos. It demonstrates the power of modern supercomputing and collaborative efforts in unravelling the mysteries of stellar life cycles.
The study was made possible through support from the Australian Research Council and the use of the Gadi supercomputer, among other resources.
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