World News – AU – Rapid radio explosions are likely caused by magnetism


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By studying the site of an amazing stellar explosion seen in April 2020, a team of scientists including several of the Anton Pannekoek Institute at the University of Amsterdam used four European radio telescopes to confirm that the most exciting mystery in astronomy is about to be solved.. Fast radio explosions, unpredictable millisecond-long radio signals that are seen over vast distances across the universe, are created by extreme stars called magnetars – and they are amazingly varied in brightness..

For more than a decade, the phenomenon known as fast bursts of radio has baffled astronomers.. These unusually bright but extremely short flashes of radio waves – lasting only milliseconds – reach Earth from galaxies billions of light-years away..

In April 2020, a burst was detected for the first time from within our galaxy, the Milky Way, by the CHIME and STARE2 radio telescopes.. The unexpected glow has been traced to a previously known source just 25,000 light-years from Earth in the constellation Vulpecula, the fox, and scientists around the world coordinated their efforts to pursue the discovery..

In May, a team of scientists led by Franz Kersten (Chalmers) directed four of Europe’s best radio telescopes toward the source, known as SGR 1935 2154.. Their findings are published today in a research paper in the journal Nature Astronomy.

“We didn’t know what to expect. Our radio telescopes have rarely been able to see fast radio bursts, and this source seems to be doing something entirely new. We were hoping to be surprised, said Mark Snilders, a team member from the Anton Pannekoek Institute of Astronomy at the University of Amsterdam!.

Radio telescopes, one dish each in the Netherlands and Poland and two at the Unsala Space Observatory in Sweden, monitored the source every night for more than four weeks after the first flash was detected, for a total of 522 hours of observation..

On the evening of May 24, the team got the surprise they were looking for. At 23:19 local time, the Westerbork Telescope in the Netherlands, the only one among the shifting group, picked up an interesting and unexpected signal: two short bursts, one fraction of a second each but 1. A difference of 4 seconds.

Kenzi Nemo, an astronomer at the Anton Paniquick Institute of Astronomy and Astron, is a member of the team..

“We’ve clearly seen two very close in time. Like the flash seen from the same source on April 28th, this sounded just like the rapid bursts of radio that we were seeing from the distant universe, but only faint.. It said the two bursts we detected on May 24 were weaker than that.

Scientists believe this is powerful new evidence linking fast radio explosions to magnetic stars. Like more distant sources of rapid radio explosions, the SGR 1935 2154 appeared to produce bursts at random intervals, and over a colossal brightness range.

«  The brightest flashes of this magnetic star are at least ten million times brighter than the weakest flash. Could this also be true, we asked ourselves, for sources of rapid radio burst outside our galaxy? If that is the case, then the magnets in the universe create beams of radio waves that can crisscross the universe all the time – and many of them could be within reach of small-sized telescopes like ours, team member Jason Hessels (Anton Panicock Institute of Astronomy and Astron) said, Netherlands).

Neutron stars are the very small and dense remnants left behind when a short-lived star more than eight times the mass of the sun explodes as a supernova. For 50 years, astronomers have studied pulsars and neutron stars that regularly send out pulses of radio waves and other radiation like clockwork.. All pulsars are thought to have strong magnetic fields, but magnetic stars are the most powerful known magnets in the universe, and each has a magnetic field hundreds of trillions of times stronger than the Sun.. .

In the future, the team aims to keep radio telescopes monitoring SGR 1935 2154 and other nearby magnetic stars, in hopes of determining how these extreme stars actually create short bursts of radiation..

Scientists have provided several ideas about how quickly the radio bursts can be created. Franz Kersten, astronomer at the Onsala Space Observatory, Chalmers, who led the project, expects the continuing rapid pace of understanding the physics behind rapid radio bursts.. .

“The fireworks from this amazing nearby star have given us intriguing clues about how quickly radio bursts can be created. The bursts we detected on May 24 could indicate a major perturbation in the star’s magnetosphere, near its surface. Other possible explanations, such as shock waves further away from the magnetar, seem less likely, but I would be happy to be wrong.. Whatever the answers, he said, we can expect new measurements and new surprises in the coming months and years.

Franz Kersten et al., Detection of two bright radio streams from the SGR 1935 2154 magnet, in Natural Astronomy, November 16, 2020. (Free version: https: // arxiv. org / abs / 2007. 05101)

Fast Radio Explosion, Magnetic Star, Star, Observer, Pulsar

World News – Australia – Fast radio explosions likely caused by magnetic stars


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