Calculations on one of the world’s fastest supercomputers have allowed UK astrophysicists to shed light on what triggers gamma-ray bursts, the most powerful explosions in the universe.
After four decades of intense research into these enigmatic gamma-ray flashes, scientists have a good idea about the objects that can provide the enormous amounts of energies required: giant stars, or colliding compact stars.
The problem now is how all that energy can escape in less than a second. On Tuesday 8 April at the UK/Ireland National Astronomy Meeting in Dublin, Stephan Rosswog from the University of Leicester will present an explanation for this enigma.
Dr Rosswog’s computer simulations, performed on the United Kingdom Astrophysical Fluids Facility (UKAFF), have now shown that the rapidly-spinning remains of colliding neutron stars can generate enormously strong magnetic fields, much the same as any magnetic field on Earth but many billion times stronger.
These ultra-strong magnetic fields can carry energy away from the collapsed remains of the two stars where it can escape in the form of gamma rays. This process is similar to that powering pulsars but the enormous magnetic field and the extremely fast spin (thousands of times per second) allows the energy to escape in less than a second rather than over many million years as in the case of pulsars.
“It is probably the biggest mystery of modern astronomy,” says Stephan Rosswog. “These beasts were discovered almost four decades ago, but it is only now that we are beginning to shed light on what is at the heart of these tremendous explosions”.
“They come in two flavours,” explains Cambridge Astronomer Enrico Ramirez-Ruiz. “Long bursts go on for several tens of seconds while a typical short burst is over in a fraction of a second”.
“Recent observations seem to tell us that long bursts are the death throes at the end of the lifetime of very massive stars,” adds Melvyn Davies, also based at Leicester University, “but these short bursts are still even more of a mystery.”
