Repeating
radio signals coming from a mystery source far beyond the Milky Way
have been discovered by scientists. While one-off fast radio bursts
(FRBs) have been detected in the past, this is the first time multiple
signals have been detected coming from the same place in space.
FRBs
are radio signals from deep space that last for just a few
milliseconds. Since their discovery over a decade ago, scientists have
been searching for more to try to understand their origin. At present,
there are several theories as to what they could be, with most involving
some cataclysmic event like a supernova or a neutron star collapsing
into a black hole.
All
of the events seen so far appear to have been one-offs, with subsequent
observations failing to find follow-up bursts coming from the same
position as the original. However, an international team of researchers
has now discovered an additional 10 bursts coming from the same
direction as FRB 121102, using the Arecibo radio telescope in Puerto
Rico.
Publishing their findings in the journal Nature,
the researchers report the subsequent bursts have the same dispersion
measures and sky positions as the original FRB. This, they say, means
the source must have survived whatever event caused the FRB to be
produced in the first place – i.e. it cannot have been a cataclysmic
one-off event. They also found the bursts differed in brightness from
other FRBs, suggesting a different source.
Paul Scholz, from
McGill University, was the first person to notice the repeating burst:
"I knew immediately that the discovery would be extremely important in
the study of FRBs."
Arecibo telescopeDanielle FutselaarIn
the study, researchers suggest the repeating bursts are coming from a
very young neutron star. "Although there may be multiple physical
origins for the population of fast radio bursts, these repeat bursts
with high dispersion measure and variable spectra specifically seen from
the direction of FRB 121102 support an origin in a young, highly
magnetised, extragalactic neutron star," they wrote.
The team now
hopes to identify the galaxy from which the repeating FRBs came from.
"Once we have precisely localised the repeater's position on the sky, we
will be able to compare observations from optical and X-ray telescopes
and see if there is a galaxy there," said Jason Hessels, corresponding
author on the study. "Finding the host galaxy of this source is critical
to understanding its properties."
Their study follows another paper on FRBs published earlier this month. Also appearing in Nature, researchers announced the discovery of the location and host galaxy of another FRB first discovered in April last year.
They
found FRB 150418 had emanated from an elliptical galaxy six billion
light years away. Unlike FRB 121102, this burst did not repeat, leading
scientists to say it was probably produced by merger event, where two
stars that are orbiting each other come together. In the paper, the team
also said they believe there are at least two different sources of
FRBs.
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