For the first time, astronomers have seen inside the very heart of a star as it explodes, confirming theories about what happens during a star's nova phase.
The international team did this by using radio telescopes in Europe and America, which allowed them to track and image the explosion.
Until now, scientists did not know how a star undergoing nova produced the high energy radiation of gamma rays. Now, however, they've seen the process in action.
A nova is common in binary star systems. It happens when the gas from one star in the system hits a white dwarf star, which creates a huge nuclear explosion on the white dwarf. That explosion sends gas into space at millions of miles per hour and creates an area of extreme brightness.
It's that brightness that triggers astronomers on Earth to point their most powerful telescopes at that region of space with hopes of witnessing the event.
Telescopes all over the world viewed this particular explosion, but astronomers didn't expect to pick up evidence of gamma ray emissions. NASA's Fermi spacecraft, however, detected gamma rays from this particular nova in 2012, in a binary star system just 6,500 light-years from Earth. Earth-based telescopes picked up radio waves from the area, suggesting that particles were moving almost as fast as the speed of light.
"These explosions are unpredictable, so when one goes off, the pressure is on for us to try and get as many of the world's telescopes as possible to take a look before it fades away," says Tim O'Brien of the Jodrell Bank Observatory at the University of Manchester. "For this nova, our international team was primed and ready to go and we really came up trumps."
Further observations from other telescopes allowed the scientists to put together a full picture of what was going on deep inside the nova. They witnessed how the white dwarf and the other star lost energy from their orbits, which sped up particles around the white dwarf's poles and boosted the explosion. The fast energy around the poles hit the slow-moving energy in orbit and created a shock wave that resulted in gamma rays.
We have detected gamma rays before, but this is the first time we've seen the process that creates them. Scientists believe that gamma rays are common when a star in a binary system goes nova and hope that this new knowledge leads to a greater understanding of how binary star systems form.
"We may be able to use novae as a 'testbed' for improving our understanding of this critical stage of binary evolution," says Laura Chomiak of Michigan State University.
