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Mystery signal coming from inside the Milky Way is repeating itself

Updated: Dec 21, 2020

Artist's impression of a powerful X-ray burst erupting from a magnetar, the suspected source of so-called fast radio bursts (FRBs)

The first burst of cosmic radio waves to be detected within our galaxy is repeating, according to scientists, shedding new light on one of the great mysteries of the universe. The ultra-bright flashes of energy, more powerful than those emitted by the sun, come from a young star about 30,000 light-years from Earth.

Multiple telescopes detected a cosmic signal coming from the star in April, and in a new paper, scientists reveal that it has repeated twice in the months since. Known as fast radio bursts (FRBs), these high-intensity emissions usually last only a fraction of a second.

FRBs were first detected in 2007, but almost all that have been detected so far were too far away to clearly make out where they came from. More than 100 have been discovered to date, but only a handful have repeated and fewer still in a predictable pattern. This makes them notoriously difficult to study, meaning their origins have eluded scientists for over a decade. Researchers say their recently discovered radio flares are the closest FRBs identified to date and come from an object known as a magnetar. Magnetars are a type of neutron star with a hugely powerful magnetic field — only a handful of them are thought to be present in the Milky Way. Physicists have previously speculated that magnetars might produce FRBs, but there was no evidence to prove that.

It means the signals don’t come from alien civilizations, a theory touted by some UFO hunters but widely dismissed by the scientific community. The new research, published in the journal Nature Astronomy on Monday, builds upon a ground-breaking paper released earlier this month about the FRB — known as FRB 200428. That study confirmed the signal from the magneton star SGR 1935+2154 was a fast radio burst. This week’s research reveals that two new bursts of varying intensity have been emitted from the star since April — meaning the burst repeats. Using four European radio telescopes, researchers led by Chalmers University in Sweden monitored the burst’s source every night for four weeks following its discovery. On May 24, the Westerbork Radio Telescope in the Netherlands caught 2-millisecond radio bursts from the magnetar, 1.4 seconds apart.

"We clearly saw two bursts, extremely close in time,” said team member Dr. Kenzie Nimmo of the University of Amsterdam.

“Like the flash seen from the same source on April 28, this looked just like the fast radio bursts we’d been seeing from the distant universe, only dimmer. The two bursts we detected on May 24 were even fainter than that,” she added. The study provides strong new evidence linking FRBs to magnetars, hinting that one of the universe’s greatest mysteries is about to be solved. The fact that the bursts are of different strengths suggests that more than one process within the stars may produce the cosmic signals.

However, questions remain as to how magnetars produce FRBs. Dr. Kiyoshi Masui, a physicist who studies FRBs at Massachusetts Institute of Technology, said earlier this year: “We’re trying to piece together what it all means.” “We’ve got our eyes open for other magnetars, but the big thing now is to study this one source and really drill down to see what it tells us about how FRBs are made.”

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