Astronomers have detected a so-called fast radio burst from around 6 billion light-years away, one of less than two dozen such events they’ve discovered in the past ten years – and this time they have clues about its source.

Fast radio bursts (FRBs) – mysterious bursts of energy from space that appear as a short flashes of radio waves to telescopes on Earth – have baffled astronomers since they were first reported nearly a decade ago. While only 16 have ever been recorded, they believe there could be thousands of FRBs a day.

By poring over 650 hours of data from NRAO’s Green Bank Telescope (GBT), an international group of astronomers uncovered the most detailed record ever of a FRB.

The group, led by Dr Kiyoshi Masui from the University of British Columbia, analyzed nearly 40 terabytes of GBT data and identified more than 6,000 FRB candidates.

They then analyzed the data from each of the signals, winnowing the field until only one candidate – dubbed FRB 110523 – remained.

“Hidden within an incredibly massive dataset, we found a very peculiar signal that matched all the known characterizes of a FRB, but with a tantalizing extra element that we simply have never seen before,” said team member Dr Jeffrey Peterson, of Carnegie Mellon University.

According to the astronomers, FRB 110523 originated around six billion light-years away inside a highly magnetized region of space, possibly linking it to a supernova or the interior of an active star-forming nebula.

They discovered that this FRB exhibited Faraday rotation, a corkscrew-like twist radio waves acquire by passing through a powerful magnetic field.

Additional analysis revealed that it also passed through two distinct regions of ionized gas, called screens, on its way to Earth.

“We now know that the energy from this FRB passed through a dense, magnetized region shortly after it formed,” Dr Masui said.

“This significantly narrows down the source’s environment and type of event that triggered the burst.”

By using the interplay between the two screens, the team was able to determine their relative locations. The strongest screen is very near the burst’s source – within nearly 100,000 light-years – placing it inside the source’s galaxy.

Only two things could leave such an imprint on the signal, the astronomers note: a dense nebula associated with the source or a location within the central region of its host galaxy.

“Taken together, these remarkable data reveal more about an FRB than we have ever seen before and give us important constraints on these mysterious events,” Dr Masui said.

“We also have an exciting new tool to search through otherwise overwhelming archival data to uncover more examples and get closer to truly understanding their nature.”

This research was presented in a paper entitled “Dense magnetized plasma associated with a fast radio burst”, by K. Masui et al., which appeared in the journal Nature.

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Kiyoshi Masui et al. Dense magnetized plasma associated with a fast radio burst. Nature, published online December 02, 2015; doi: 10.1038/nature15769