What triggers a supernova?

6 October 2020

A multinational team of scientists, including Dr Lap-Ming Lin (Croucher Fellowship 2004), of Chinese University of Hong Kong, has become the first to successfully examine the phase transition that may trigger a supernova, the powerful explosion of a star that takes place at the end of its life cycle. Such explosions are so violent that the energy released can be equivalent to the total energy radiated by our sun over its entire lifespan of 10 billion years.

The study of supernovae is also a crucial step towards finding the origin of life. The explosions spread the heavy elements produced in stars, such as carbon and iron, out to the interstellar medium, and these ashes form the raw materials of the next generation of stars and planets, such as our sun and earth.

Astrophysicists generally believe that a supernova occurs when energy is released due to the breakdown of electrons into protons and neutrons inside the star. At the last moments before the explosion, protons and neutrons undergo one more transformation – breaking down into smaller components called quarks and gluons. This stage is called the quantum chromodynamics (QCD) phase transition.

Using state-of-the-art multidimensional computer simulations of supernova, the research team from CUHK, Stockholm University in Sweden, and Michigan State University in the US, has now observed unique imprints of the QCD phase transition on the gravitational wave and neutrino signals emitted.

New and distinguishable features of the emitted gravitational waves that emerge as a result of the QCD phase transition in the supernova core include high frequency (~3,000 Hz), large amplitude, and a short duration (less than 5 milliseconds).

These show that gravitational waves and neutrinos can potentially become powerful new probes for supernova cores. For example, future detection of such gravitational-wave signals, coinciding with a burst of neutrinos, would provide strong evidence for the transformation of supernova core matter into quarks and gluons.

The breakdown of protons and neutrons to quarks in the stellar core provides a viable engine to trigger the supernova.

The study was published and selected as an Editors’ Suggestion in Physical Review Letters.

Dr Lap-Ming Lin received his BSc (First Class Honours) and MPhil from the Chinese University of Hong Kong, and PhD from Washington University in St Louis, US. He was awarded a Croucher Foundation Fellowship in 2004, carrying out his postdoctoral research at the Observatory of Paris-Meudon, France. His research interests span relativistic astrophysics, gravitational wave sources, and numerical relativity. He is now a Lecturer in the Department of Physics at the Chinese University of Hong Kong. 

To view Dr Lin's Croucher profile, please click here.