Exploring the site of a spectacular stellar explosion seen in April 2020, a team of Chalmers-led scientists used four European radio telescopes to confirm that the most exciting puzzle of astronomy was about to be solved. Fast radio bursts, unpredictable millisecond radio signals observed over vast distances in the universe, are generated by extreme stars called magnetars ̵
For more than a decade, the phenomenon known as fast radio waves has excited and puzzled astronomers. These unusually bright but extremely brief flashes of radio waves – lasting only milliseconds – reach Earth from galaxies billions of light-years away.
In April 2020, for the first time, one of the explosions was discovered by our galaxy, the Milky Way, by the CHIME and STARE2 radio telescopes. The unexpected eruption was traced to a previously known source just 25,000 light-years from Earth in the constellation Vulpecula, the Fox, and scientists from around the world coordinated their efforts to track the discovery.
In May, a team of scientists led by Franz Kirsten (Chalmers) directed four of the best radio telescopes in Europe to the source known as SGR 1935 + 2154. The results were published today in an article in the journal Natural astronomy.
“We didn’t know what to expect. Our radio telescopes could rarely see fast radio waves, and this source seemed to be doing something completely new. We were hoping to be surprised,” said Mark Snelders, a member of the Anton Panekoek Institute of Astronomy at the University of Amsterdam.
Radio telescopes, one dish each in the Netherlands and Poland and two at the Onsala Space Observatory in Sweden, observed the source every night for more than four weeks after the discovery of the first flash, a total of 522 hours of observation.
On the evening of May 24, the team received the surprise they were looking for. At 11:19 p.m. local time, the Westerbork telescope in the Netherlands, the only one on duty, caught a dramatic and unexpected signal: two short bursts, each one millisecond long but 1.4 seconds apart.
Kenzi Nimo, an astronomer at the Anton Panekoek Institute of Astronomy and ASTRON, is a member of the team.
“We clearly saw two bursts, extremely close in time. Like the flash seen from the same source on April 28, it looked just like the rapid radio bursts we had seen from the distant universe, only fainter. The two bursts we found on May 24 was even weaker than that, “she said.
These are new, strong pieces of evidence linking fast radio waves to magnetars, scientists say. Like more distant sources of fast radio bursts, SGR 1935 + 2154 seemed to produce bursts at random intervals and in a huge range of brightness.
“The brightest flashes of this magnetar are at least ten million times brighter than the faintest. We wondered if this could be true for sources of fast radio bursts outside our galaxy? If so, then the magnets of the universe. they create radio waves that could cross space all the time – and many of them could be within the reach of modest telescopes like ours, “said team member Jason Hessels (Anton Panekoek Institute of Astronomy and ASTRON, The Netherlands).
Neutron stars are tiny, extremely dense debris left after a short-lived star with more than eight times the mass of the Sun explodes like a supernova. For 50 years, astronomers have studied pulsars, neutron stars that send clockwise pulses to radio waves and other radiation. All pulsars are thought to have strong magnetic fields, but magnetars are the strongest known magnets in the universe, each with a magnetic field hundreds of trillions of times stronger than the sun’s.
In the future, the team aims to keep the radio telescopes that monitor SGR 1935 + 2154 and other nearby magnetars, hoping to determine how these extreme stars actually make their short broadcasts.
Scientists have presented many ideas about how fast radio bursts are generated. Franz Kirsten, an astronomer at the Onsala Space Observatory, Chalmers, who is leading the project, expects the rapid pace of understanding the physics behind fast radio waves to continue.
“The fireworks from this amazing, nearby magnetar gave us exciting clues as to how quickly radio bursts can be generated. The explosions we found on May 24 could show dramatic disturbances in the star’s magnetosphere near its surface. Other possible explanations. “Shock waves farther from the magnetar seem less likely, but I’ll be happy to be wrong. Whatever the answers, we can expect new measurements and new surprises in the coming months and years,” he said.
Luck of luck: Astronomers discover a cosmic source of a radio burst
F. Kirsten et al. Detection of two bright radio bursts by magnetar SGR 1935 + 2154, Natural astronomy (2020). DOI: 10.1038 / s41550-020-01246-3
Provided by Chalmers University of Technology
Quote: Space flashes come in different sizes (2020, November 16), retrieved on November 17, 2020 from https://phys.org/news/2020-11-cosmic-sizes.html
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