Scientists create mini-supernova shock waves
Researchers have created a miniature version of supernova shock waves in a lab here on Earth to solve a long-standing cosmic mystery. When stars die and explode in supernovae, they create shock waves. These powerful shock waves blast out cosmic rays, or highly energetic particles, into the universe. The waves act almost like particle accelerators, pushing these particles out so fast that they approach the speed of light. However, scientists have yet to fully understand exactly how and why the shock waves accelerate these particles. “These are fascinating systems, but because they are so far away it’s hard to study them,” said Frederico Fiuza, who led the new study. To better study these cosmic shock waves, scientists brought them to Earth. Well, not literally, but researchers have created a scaled-down version of supernova remnants. “We are not trying to make supernova remnants in the lab, but we can learn more about the physics of astrophysical shocks there and validate models,” Fiuza said. Fiuza and his colleagues worked to create a fast, diffuse shock wave that could mimic the shocks that follow a supernova. The scientists worked at the National Ignition Facility, a Department of Energy facility at the Lawrence Livermore National Laboratory in California. They shot powerful lasers at carbon sheets to create two plasma flows, targeted at each other. When the plasma flows collided, they created a shock wave “in conditions similar to a supernova remnant shock”. The scientists observed the experiment using both optical and X-ray technology. By studying a miniature analogue of the cosmic phenomenon here on Earth, the researchers verified that the shock was capable of accelerating electrons to nearly the speed of light. However, the mystery of exactly how these electrons reached such speeds remains, which prompted the scientists to turn to computer modelling. “We can’t see the details of how particles get their energy even in the experiments, let alone in astrophysical observations, and this is where the simulations really come into play,” says co-author Anna Grassi. While the cosmic mystery of the shock waveaccelerated particles remains, computer models created by Grassi revealed one possible solution. According to these models, turbulent electromagnetic fields within the shock wave could accelerate electrons to the speeds observed. Fiuza, Grassi and their colleagues will continue to investigate the X-rays emitted by the accelerated electrons and hone their computer simulations, according to a statement. Other future research will study positively charged protons blasted by the shock wave in addition to the electrons studied in this work.