Astronomers detect mysterious 8 billion-year-old energetic burst
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[October 21, 2023]
By Will Dunham
WASHINGTON (Reuters) - Astronomers have detected an intense flash of
radio waves coming from what looks like a merger of galaxies dating to
about 8 billion years ago - the oldest-known instance of a phenomenon
called a fast radio burst that continues to defy explanation.
This burst in less than a millisecond unleashed the amount of energy our
sun emits in three decades, researchers said. It was detected using the
Australian SKA Pathfinder, a radio telescope in the state of Western
Australia. Its location was pinpointed by the European Southern
Observatory's Very Large Telescope in Chile, one of the most powerful
optical telescopes.
A fast radio burst, or FRB, is a pulse of radio-frequency
electromagnetic radiation. It lasts a small fraction of a second but
outshines most other sources of radio waves in the universe. Radio waves
have the longest wavelengths in the electromagnetic spectrum.
"The radio waves in FRBs are similar to those used in microwave ovens.
The amount of energy in this FRB is the equivalent to microwaving a bowl
of popcorn twice the size of the sun," said astronomer Ryan Shannon of
Swinburne University of Technology in Australia, co-leader of the study
published this week in the journal Science.
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Until now, the oldest-known such burst dated to 5 billion years ago,
making this one 3 billion years older. The universe is about 13.8
billion years old. For comparison, Earth is about 4.5 billion years old.
In seeing objects and events from long ago, astronomers peer across vast
cosmic distances, making this burst also the farthest of any FRB ever
detected.
"We now know that fast radio bursts have been around for more than half
the age of the universe," said astronomer and study co-leader Stuart
Ryder of Macquarie University in Australia.
Fast radio bursts were discovered in 2007.
"The most likely source is a hyper-magnetized neutron star, called a
magnetar. These stars are stellar corpses the mass of the sun but only
the size of a small city. They are some of the most extreme objects in
the universe, which you would need to produce such extreme bursts,"
Shannon said.
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![](../images/102123PIX/news_e10.jpg)
This artist's impression, not to scale, illustrates the path of a
fast radio burst from the distant galaxy where it originated all the
way to Earth, in one of the Milky Way galaxy's spiral arms, in this
handout picture obtained on October 20, 2023. ESO/M. Kornmesser/Handout
via REUTERS
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"There are more energetic events in the universe, associated with
stellar explosions or a black hole shredding a star apart. But FRBs
are unique in that they produce all their energy in radio waves,
with nothing seen in other bands - optical light or X-rays for
example - and that the signals are so short," Shannon added.
They also are more common, Shannon added, with upwards of 100,000
thought to occur somewhere in the universe daily. Far fewer have
been detected, Shannon said, and only around 50 - including this one
- have been traced back to the galaxy where they originated.
"Galaxies in the distant universe look different than those nearby -
they don't have nice spiral arms - so it wasn't clear if what we
were seeing was one galaxy with a few clumps, or a few smaller
galaxies. It is likely that the source is a few galaxies, possibly
merging," Shannon said.
The researchers said that studying these bursts also can help to
detect and measure the immense amount of matter believed to populate
the expanses of space between galaxies. As these radio waves zip
though the cosmos, they can flag the presence of this intergalactic
plasma - gas so hot that some or all its atoms are split into the
subatomic particles electrons and ions.
"Most of the normal matter in the universe - this is the regular
matter that makes up stars, planets, humans - is thought to reside
in a diffuse cosmic web of gas between galaxies," Shannon said.
"People have been searching for this matter for decades using other
techniques. Because it is so diffuse, it is nearly invisible in any
other way, so was considered 'missing.'"
(Reporting by Will Dunham; Editing by Daniel Wallis)
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