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In a paper published in Science, Bannister et al. describe
observations with ASKAP to determine the precise location of a Fast
Radio Burst (FRB). The galaxy from which the burst originated was
then imaged by three of the world's largest optical telescopes - Keck,
Gemini South and the European Southern Observatory's Very Large
Telescope. Fast radio bursts last less than a millisecond, making it
difficult to accurately determine where they have come from. Most
FRBs are "one-offs" but a small fraction are "repeaters" that recur in
the same location. In 2017 astronomers identified a repeating FRB's
home galaxy but localising a one-off burst has been much more
challenging. ASKAP was able to pinpoint the location of FRB 180924 to
its home galaxy (DES J214425.25-405400.81), with the high-resolution
image showing that the burst originated in the outskirts of a Milky
Way-sized galaxy about 3.6 billion light-years away. The image above,
obtained with ESO's 8-m Very Large Telescope, shows the host galaxy
with the FRB location marked by the black circle. The redshift of the
galaxy, indicating its distance, was measured with spectra obtained
with 10-m Keck telescope in Hawai'i and the 8-m Gemini South telescope
in Chile. While only a millisecond or so in duration at any
frequency, FRBs are dispersed in time, with lower frequencies arriving
later than higher frequencies. The amount of dispersion depends on
the amount of matter the radio waves traverse in reaching the Earth.
By pinpointing their position, FRBs can be used to measure the amount of
matter in intergalactic space, potentially revealing material that
astronomers have struggled for decades to find.
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