Laser hints at how Universe got its magnetism

Magnetic fields exist throughout galactic and intergalactic space, what is puzzling is how they were originally created and how they became so strong.

A team, led by Oxford University physicists, used a high-power laser to explode a rod of carbon, similar to pencil lead, in helium gas. The explosion was designed to mimic the cauldron of plasma – an ionized gas containing free electrons and positive ions – out of which the first galaxies formed.

The team found that within a microsecond of the explosion strong electron currents and magnetic fields formed around a shock wave. Astrophysicists took these results and scaled them through 22 orders-of-magnitude to find that their measurements matched the ‘magnetic seeds’ predicted by theoretical studies of galaxy formation.

A report of the research is published in this week’sNature.

‘Our experiment recreates what was happening in the early Universe and shows how galactic magnetic fields might have first appeared,’ said Dr Gianluca Gregori of Oxford University’s Department of Physics, who led the work at Oxford. ‘It opens up the exciting prospect that we will be able to explore the physics of the cosmos, stretching back billions of years, in a laser laboratory here on Earth.’

The results closely match theories which predict that tiny magnetic fields – ‘magnetic seeds’ – precede the formation of galaxies. These fields can be amplified by turbulent motions and can strongly affect the evolution of the galactic medium from its early stages.

Dr Gregori said: ‘In the future, we plan to use the largest lasers in the world, such as the National Ignition Facility at the Lawrence Livermore National Laboratory in California (USA), to study the evolution of cosmic plasma.’

The experiments were conducted at the Laboratoire pour l’Utilisation de Lasers Intenses laser facility in France. The team included scientists from; Oxford University, Rutherford Appleton Laboratory, Laboratoire pour l’Utilisation de Lasers Intenses, University of Strathclyde, University of California Los Angeles, University of Michigan, University of York, Osaka University, Lawrence Livermore National Laboratory, ETH-Zurich.

A report of the research, ‘Generation of scaled protogalactic seed magnetic fields in laser-produced shock waves’, is published in this week’s Nature.