Scientists have captured the most powerful type of explosion in the universe in unprecedented detail – a gamma ray burst. Their detailed observations could help them solve some of the most fundamental questions in astrophysics – such as how these massive explosions are powered and how black holes are formed.
Gamma ray bursts are bright flashes of high-energy light that are thought to represent the birth of a distant black hole, forming from the remnants of a large star dying in a supernova explosion. However, there was still a lot of questions about how a gamma-ray burst evolves as the dying star collapses to become a black hole.
Furthermore, the prodigious energy released during these explosions has long puzzled scientists, and the fact they only last a few milliseconds has made it hard to observe them.
"Gamma-ray bursts are catastrophic events, related to the explosion of massive stars 50 times the size of our sun. If you ranked all the explosions in the universe based on their power, gamma-ray bursts would be right behind the Big Bang," Eleonora Troja, lead author of the paper describing the discovery, from the University of Maryland, said in a statement.
"In a matter of seconds, the process can emit as much energy as a star the size of our sun would in its entire lifetime. We are very interested to learn how this is possible."
Traditional ground-based telescopes have been slow to capture the fast-fading light from gamma ray bursts, but recently, great technological advances have made it easier to detect and investigate the explosions.
By an incredible one-in-10,000 chance, the international team was able to see the light from a gamma ray burst located 10 billion light years away from Earth. Using novel, autonomous robotic telescopes, the scientists succeeding not only in measuring how the light was produced by the material ejected into space during the explosion, but also to measure a unique property of the light known as 'polarisation'.
"Gamma ray bursts occur completely randomly in space and time, so we cannot predict where or when one will appear. What made these observations possible is a combination of progress in robotic telescope technology, a geographical spread of telescopes all over the world and the properties of this particular gamma ray burst," co-author Carole Mundell, head of physics at the University of Bath, told IBTimes UK.
"It was very bright and produced a very short flare that lasted just 1 second before the main explosion began, so our telescopes were ready to capture the visible light at the same time as the high energy gamma rays from the explosion itself. It was so bright, it could have been seen through binoculars. This is rare."
Settling long-standing debates
This most detailed picture ever of a gamma ray burst has allowed the scientists to find out more about what powers gamma ray bursts.
"By measuring polarisation of the early burst, we learnt more about the nature of the light that is produced. There had been a big debate about how it's produced. Here, we were able to identify a type of light known as synchrotron radiation," Mundell said.
Synchrotron radiation - which occurs when electrons are accelerated in a curved or spiral pathway - was found to power the initial, extremely bright phase of the burst, known as the prompt phase.
"Our study provides convincing evidence that the prompt gamma-ray burst emission is driven by synchrotron radiation. This is an important achievement because, despite decades of investigation, the physical mechanism that drives gamma-ray bursts had not yet been unambiguously identified," Troja explained.
These observations may also improve the scientists' understanding of how black holes form. By analysing polarisation data that spanned nearly the entire time-frame of the burst, they were indeed able to identify the presence of a magnetic field and track how it evolved during the explosion.
The data they collected suggest that strong magnetic fields form close to newly formed black holes and drive energy and material outwards in a tightly focused beam.
The complete findings are published in the journal Nature.