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SPACE SCIENCES
Researchers have known since 1983 that gamma-ray bursts can ionise Earth’s atmosphere
and thus disturb the great wave guide. This appears to be the first time anyone has
recorded the effect using an earth probe antenna.
The outburst on 9 October shocked astronomers.
Phil Evans of the University of Leicester tweeted on the immediate aftermath of the
burst: “It’s bright, really bright. Like stupidly, really bright.” Evans works with data from
NASA’s Swift gamma-ray observatory, and the overflowing signal had apparently broken
some of his plotting software.
Researchers have since pinpointed the burst. It came from a dusty galaxy 2.4 billion
light years away, almost certainly triggered by a supernova explosion giving birth to a
black hole. This is the closest gamma-ray burst (GRB) ever recorded, thus accounting for
its extreme intensity.
using the Gemini South telescope in
Chile.
Meanwhile, other observers in the
UK and Germany have also reported
ionospheric disturbances resulting from
the burst. They all used regular above-
ground antennas.
When black holes form, they drive
powerful jets of particles that are
accelerated to nearly the speed of light.
These jets then pierce through what
remains of the progenitor star, emitting
X-rays and gamma rays as they stream
into space. If these jets are pointed in
the general direction of Earth, they are
observed as bright flashes of X-rays and
gamma rays.
Another gamma-ray burst this bright
may not appear for decades or even
centuries. n
The first observation of an ionospheric
disturbance from a gamma-ray
occurred at 22:14:18 UTC on 1 August
1983 and was one of the strongest
ever observed. The total fluence
was 2 x 10 erg cm , most of which
–3
–2
occurred in the first four seconds of
the burst. Simultaneously, a change
Swift’s X-Ray telescope captured the afterglow of GRB 221009A about an hour after it was observed in the amplitude of
was first detected. The bright rings form as a result of X-rays scattered by otherwise a very-low-frequency (VLF) radio
unobservable dust layers within our galaxy that lie in the direction of the burst. signal from a transmitter in Rugby,
The dark vertical line is an artifact of the imaging system. England, monitored at Palmer
Credit: NASA/Swift/A. Beardmore (University of Leicester) Station, Antarctica, indicative of an
ionospheric disturbance. Weaker
“In our research group, we’ve been referring to this burst as the ‘BOAT’, or Brightest disturbances were also recorded at
Of All Time, because when you look at the thousands of bursts gamma-ray telescopes the same receiving site on signals
have been detecting since the 1990s, this one stands apart,” says Jillian Rastinejad, an from VLF stations in Annapolis,
astronomer at Northwestern University who has been monitoring the burst’s afterglow Maryland and Lualualei, Hawaii.
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