Antimatter plasma reveals secrets of deep space signals

Mysterious radiation emitted from distant corners of the galaxy could finally be explained with efforts to recreate a unique state of matter that blinked into existence in the first moments after the Big Bang.

For 50 years, astronomers have puzzled over strange radio waves and gamma rays thrown out from the spinning remnants of dead stars called pulsars.

Researchers believe that these enigmatic, highly-energetic pulses of radiation are produced by bursts of electrons and their antimatter twins, positrons. The universe was briefly filled with these superheated, electrically charged particles in the seconds that followed the Big Bang before all antimatter vanished, taking the positrons with it. But astrophysicists think the conditions needed to forge positrons may still exist in the powerful electric and magnetic fields generated around pulsars.

‘These fields are so strong, and they twist and reconnect so violently, that they essentially apply Einstein’s equation of E = mc2 and create matter and antimatter out of energy,’ said Professor Luis Silva at the Instituto Superior Técnico in Lisbon, Portugal. Together, the electrons and positrons are thought to form a super-heated form of matter known as a plasma around a pulsar.

But the exact conditions necessary to produce a plasma containing positrons remain unclear. Scientists also still do not understand why the radio waves emitted by the plasma around pulsars have properties similar to light in a laser beam – a wave structure known as coherence.

To find out, researchers are now turning to powerful computer simulations to model what might be going on. In the past, such simulations have struggled to mimic the staggering number of particles generated around pulsars. But Prof. Silva and his team, together with researchers at the University of California, Los Angeles in the United States, have adapted a computer model called OSIRIS so that it can run on supercomputers, allowing it to follow billions of particles simultaneously.

The updated model, which forms part of the InPairs project, has identified the astrophysical conditions necessary for pulsars to generate electrons and positrons when magnetic fields are torn apart and reattached to their neighbours in a process known as magnetic reconnection.

OSIRIS also predicted that the gamma rays released by electrons and positrons as they race across a magnetic field will shine in discontinuous spurts rather than smooth beams.

The findings have added weight to theories that the enigmatic signals coming from pulsars are produced by the destruction of electrons as they recombine with positrons in the magnetic fields around these dead stars.

Prof. Silva is now using the data from these simulations to search for similar burst signatures in past astronomical observations. The tell-tale patterns would reveal details on how magnetic fields evolve around pulsars, offering fresh clues about what is going on inside them. It will also help confirm the validity of the OSIRIS model for researchers trying to create antimatter in the laboratory.

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