-Obsidian aka Daniel
FRBs: Mystery repeating radio signals discovered
emanating from unknown cosmic source
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."
In 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.
More about FRBs.
