June 2, 2014
Supernova Recreation Reveals How Interstellar Magnetic Fields May Have Formed
Brett Smith for redOrbit.com - Your Universe Online
Using a laser beam 60,000 billion times more powerful than a typical laser pointer, researchers have recreated a small-scale supernova and revealed that cosmic turbulence may have boosted magnetic fields to the power seen in interstellar space, according to a new report in the journal Nature Physics."Magnetic fields are ubiquitous in the universe," said study author Don Lamb, a professor in astronomy and astrophysics at the University of Chicago. "We're pretty sure that the fields didn't exist at the beginning, at the Big Bang. So there's this fundamental question: how did magnetic fields arise?"
The study team said their work was motivated by the detection of magnetic fields in Cassiopeia A, a supernova remnant, which are about 100 times more powerful than those in surrounding interstellar space.
The supernova was recreated using the Vulcan laser facility at the UK's Science and Technology Facilities Council's Rutherford Appleton Lab.
“Our team began by focusing three laser beams onto a carbon rod target, not much thicker than a strand of hair, in a low density gas-filled chamber,” said study author Jena Meinecke, an Oxford University graduate student.
The massive quantity of heat generated over a few million degrees by the laser caused the carbon rod to blow up, generating a blast that grew out through the low density gas. The dense gas clumps or clouds that encircle an exploding star were modeled in the experiments by placing a plastic grid near the blast.
The team found that as the explosion passes through the grid it becomes disrupted and turbulent just like the images taken from Cassiopeia.
“We found that the magnetic field is higher with the grid than without it,” said Gianluca Gregori, a physics professor at Oxford University. “Since higher magnetic fields imply a more efficient generation of radio and X-ray photons, this result confirms that the idea that supernova explosions expand into uniformly distributed interstellar material isn't always correct and it is consistent with both observations and numerical models of a shockwave passing through a 'clumpy' medium.”
“It may sound surprising that a table-top laboratory experiment that fits inside an average room can be used to study astrophysical objects that are light years across,” Gergori continued. “In reality, the laws of physics are the same everywhere, and physical processes can be scaled from one to the other in the same way that waves in a bucket are comparable to waves in the ocean. So our experiments can complement observations of events such as the Cassiopeia A supernova explosion.”
The study team used a computer simulation conducted at UChicago's Flash Center for Computational Science to support their experimental observations.
"Because of the complexity of what's going on here, the simulations were absolutely vital to inferring exactly what's going on and therefore confirming that these mechanisms are happening and that they are behaving in the way that theory predicts," Meinecke said.
The study team said they plan to continue their experiments to look into new aspects of the physics they observed.
"We could look at the velocity instead of the density of the magnetic field, or we might look at the pressure," Lamb said. "This simulation is a treasure trove of information about what's really going on. It's actually critical to understanding correctly what's really happening."