A mysterious repeating radio signal from space revealed last year is now the fifth fast radio burst to be tracked back to its source galaxy.
It’s a location unlike any of the others, and astronomers are having to rethink their previous assumptions about how these signals are generated.
The origin of this repeating signal is a spiral galaxy, located 500 million light-years from Earth, making it the closest known source of what we call fast radio bursts (FRBs) yet.
And the FRBs are emanating specifically from a region just seven light-years across – a region that’s alive with star formation.
The blue points in this artist’s impression of the filamentary structure of galaxies are signals from FRBs
According to the astronomer Kenzie Nimmo of the University of Amsterdam in the Netherlands “This object’s location is radically different from that of not only the previously located repeating FRB, but also all previously studied FRBs,”.
“This blurs the differences between repeating and non-repeating fast radio bursts. It is assumed that FRBs are produced in a large zoo of locations across the Universe and just require some specific conditions to be visible.”
One of the strangest mysteries of Universe is Fast radio bursts. They are extremely brief spikes in electromagnetic radiation detected by radio telescopes, lasting no more than a few milliseconds at most. But in that time, they can discharge more energy than 500 million Suns.
Most of the fast radio bursts detected till now have appeared only once. Such a rare frequency makes them extremely difficult to trace – to date, only three have had their origin localised to a galaxy.
But in recent years, we’ve begun to find FRBs that repeat – popping off repeat signals with no discernible pattern – and in 2017, scientists managed to track down the origin of one of them.
In last year, at the CHIME experiment in Canada scientists had detected a massive eight new repeating FRBs, which brought the number of known repeaters to a total of 10. It is one of these new repeaters – a signal called FRB 180916.J0158+65 (FRB 180916 for short) – that astronomers have now traced.
In the European Very Long Baseline Interferometry Network, an international team of astronomers used eight telescopes to conduct follow-up observations in the direction of FRB 180916. Over the course of five hours, they detected four more bursts – which allowed them to home in on the source of the signal.
And that led them to a normal spiral galaxy called SDSS J015800.28+654253.0.
The first repeating fast radio burst FRB 121102 was located 3 billion light-years away. It was found to be emanating from a dwarf galaxy. Soon its signal had been distorted due to the Faraday effect, which occurs when electromagnetic radiation interacts with a magnetic field.
This led scientists to conclude that FRB 121102 was produced in an extreme environment, like the region around a supermassive black hole at the galactic centre. Interestingly, it, too, seemed to be close to a star-forming region.
The three other non-repeating FRBs, on the other hand, were found in much more conventional galaxies – but only one of them was near a star-forming region.
The another FRB 180916 was not nearly as distorted by the Faraday effect as FRB 121102, which indicates that its location was not as magnetic; and it was found pretty far from the galactic centre.
Astronomer Benito Marcotte of the Joint Institute for VLBI ERIC said: “The multiple flashes that we witnessed in the first repeating FRB arose from very particular and extreme conditions inside a very tiny (dwarf) galaxy,”.
“This discovery represented the first piece of the puzzle but it also raised more questions than it solved, such as whether there was a fundamental difference between repeating and non-repeating FRBs. Now, we have localised a second repeating FRB, which challenges our previous ideas on what the source of these bursts could be.”
There are many questions about the misteries of Universe and these findings may be considered as beginning to answer those questions.
“With the characterisation of this source, the argument against pulsar-like emission as origin for repeating FRBs is gaining strength,” said Ramesh Karuppusamy of the Max Planck Institute for Radio Astronomy in Germany.
“We are at the verge of more such localisations brought about by the upcoming newer telescopes. These will finally allow us to establish the true nature of these sources.”
The research has been published in “Nature”.