Fast radio bursts have puzzled astronomers since their discovery in 2007. Find out how scientists have revealed their origin and their variability.
We’ve written about fast radio bursts before in these pages. At that point, these blink-of-an-eye flashes from deep space were still unexplained. Ironically, they were used to solve a different mystery-the quantity of conventional matter in the Universe.
A typical fast radio burst releases as much energy in a millisecond as our Sun does in three days. Yet, by the time they reach the Earth, their signal is about 1,000 times weaker than a cellphone transmission from the moon would be. That suggests that most of them must originate in galaxies billions of light-years away from us.
Now, a team of researchers from the Chalmers University of Technology in Sweden has explained the origin of these peculiar flashes. In the process, they’ve also revealed their remarkable variety in brightness. The journal Nature Astronomy published their findings last week.
Detecting Fast Radio Bursts Since 2007
Astronomers have been detecting fast radio bursts since 2007. Duncan Lorimer of West Virginia University was the first researcher to notice one.
He had assigned his student, David Narkevic, to sift through 2001 archival data from Australia’s Parkes radio telescope. They discovered a brilliant radio burst that lasted just 5 milliseconds about 3˚ from the Small Magellanic Cloud, a small galaxy neighbouring our Milky Way.
Lorimer and Narkevic could tell that the bursts didn’t come from the Small Magellanic Cloud or the Milky Way. Beyond that, they couldn’t explain the origin of what we now call the Lorimer Burst.
Couldn’t Explain the Origin of the “Lorimer Burst”
Scientists have continued to spot these unexplained bursts from time to time. They identified six of them in 2019, and there have been three so far this year.
One of the 2020 bursts is called SGR 1935+2154. Its signal had so little dispersion that it must have come from inside our own galaxy at a distance of only 25,000 light-years.
This new, nearby source inspired radio astronomers from around the world to investigate it further. Professor Franz Kirsten of Chalmers led one of those research teams.
Four of the Best Radio Telescopes in Europe
They aimed four of the best radio telescopes in Europe at SGR 1935+2154. These were the 25-metre RT1 telescope at Westerbork, Netherlands, the 25-metre and the 20-metre telescope at Onsala Space Observatory, and the 32-metre telescope in Toruń, Poland.
The four European telescopes monitored the source of the original flash over four weeks. They watched it for four hours every night, which came to 522 hours in total.
It was close to midnight on May 24 when one of the telescopes, the Westerbork telescope in the Netherlands, captured two fast radio bursts. They were each a mere one millisecond in duration, and they were 1.4 seconds apart.
Random Intervals, Varied Enormously in Brightness
The bursts the team detected happened at random intervals and varied enormously in brightness. The brightest flashes are more than ten million times more brilliant than the dimmest ones.
The scientists concluded that this fast radio burst came from a type of star called a magnetar by reviewing all of these findings. They’ve shown this is so for SGR 1935+2154 as well as some other flashes-maybe even all of them.
When a super-massive star dies, it releases a supernova explosion. What’s left after the blast is called a neutron star.
Hundreds of Trillions of Times Stronger than Sun
Magnetars are a type of neutron star, known for their unimaginably powerful magnetic fields. A magnetar’s magnetic field is hundreds of trillions of times more potent than the magnetic field of our Sun.
As the magnetic field decays, it emits high-energy electromagnetic radiation, like X-rays and gamma rays. Magnetars differ from pulsars because their bursts happen at regular intervals, while pulsars are as stable as clockwork.
Now that scientists have worked out the origin of fast radio bursts, they have further insight into what happens during a star’s end of life process. This is important to all of us because it explains our own origins.
Important to All of Us — It Explains Our Own Origins
All of the complex chemical elements that make up the world around us, and our own bodies, come from the explosions that mark a star’s death. Those explosions emit the atoms that make life on our planet possible.
Understanding the cause of fast radio bursts, we detect will give astronomers greater insight into their strength and location. This will unveil new discoveries in the future.
Professor Kirsten concluded by saying, “the fireworks from this amazing, nearby magnetar have given us exciting clues about how fast radio bursts might be generated. Whatever the answers, we can expect new measurements and new surprises in the months and years to come.”
We always have more to learn if we dare to know.
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Originally published at http://daretoknow.ca on December 1, 2020.