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The Associated Press5 November 2020 11:24:31
A flash of luck helped astronomers solve a cosmic mystery: What causes powerful but fleeting radio bursts that dart and zigzag across the universe? Scientists have known about these energy pulses – called fast radio bursts – for about 13 years and have seen them come from outside our galaxy, which makes it harder to pinpoint what causes them. Making it even more difficult is that they happen so quickly, in a couple of milliseconds.
Then, this April, a rare but considerably fainter burst from inside our Milky Way galaxy was spotted by two different telescopes: one of antennas hand-made by a California doctoral student, which included real baking trays, l another $ 20 million Canadian observatory.
They tracked that fast radio flash to a weird kind of star called a magnetar it’s 32,000 light-years from Earth, according to four studies in Wednesday’s diary Nature.
It was not just the first fast radio burst from a source, but the first from our galaxy. Astronomers say there may be other sources for these explosions, but they are now sure of a culprit: magnetars.
Magnetars are incredibly dense neutron stars, with 1.5 times the mass of our sun squashed into a space the size of Manhattan. They have huge magnetic fields that hum and crackle with energy, and sometimes flare of X-rays and radio waves erupt from them, according to McGill University astrophysicist Ziggy Pleunis, co-author of the Canadian study.
The magnetic field around these magnetars “is so strong that every nearby atom is torn apart and you can see weird aspects of fundamental physics,” said astronomer Casey Law of the California Institute of Technology, who was not part of the research. .
There are perhaps a dozen or so of these magnetars in our galaxy, apparently because they are so young and part of the star birth process, and the Milky Way is not as rich in stellar births as other galaxies, said Shami Chatterjee of Cornell University. , which was not part of either discovery team.
This explosion in less than a second contained about the same amount of energy that our sun produces in a month, and is still much weaker than the detected radio bursts from outside our galaxy, Caltech radio astronomer Christopher Bochenek said. He helped locate the burst with hand-made antennas.
These radio bursts are not dangerous to us, not even the most powerful ones outside our galaxy, the astronomers said.
Those that come from outside our galaxy and travel millions or billions of light years are “tens of thousands to millions of times more powerful than anything we have detected in our galaxy,” said co-author Daniele Michilli, an astrophysicist at McGill. and part of the Canadian team.
Scientists think they are so frequent that they could happen more than 1,000 times a day outside our galaxy. But finding them isn’t easy.
“You had to look in the right place at the right millisecond,” said Cornell’s Chatterjee. “Unless you’ve been very, very lucky, you won’t see one of these.”
While this is a frequent occurrence outside the Milky Way, astronomers have no idea how often these explosions occur within our own galaxy.
“We still don’t know how lucky we have been,” Bochenek said. “This could be something once every five years or some events could happen every year.”
Bochenek’s antennas cost around $ 15,000. Each is “the size of a large bucket. It’s a 6-inch piece of metal tube with two literal cake pans around it, “the graduate student said. They’re rudimentary tools designed to look at a giant piece of sky – about a quarter of it – and see only the brightest of radio flashes.
Bochenek thought he had perhaps a 1 in 10 chance of spotting a fast radio blast in a few years. But after a year, the salary hit.
The Canadian observatory in British Columbia is more focused and refined but aims at a much smaller portion of the sky and has been able to locate the source of the magnetar in the constellation Vulpecula.
Because the explosions are affected by all the material they pass through in space, astronomers may be able to use them to better understand and map the material invisible to us between galaxies and “weigh” the universe, said Jason Hessels, chief astronomer. from the Dutch Institute for Radio Astronomy, which was not part of the research.
Astronomers have had as many as 50 different theories about what causes these fast radio bursts, including aliens, and point out that magnetars may not be the only answer, especially since there appear to be two types of fast radio bursts. Some, like the one spotted in April, only happen once, while others often recur.
Michilli said his team has tracked an explosion that occurs every 16 days in a nearby galaxy and is moving closer to locate the source.
Some of these young magnetars are only a few decades old, “and that’s what gives them enough energy to produce repeated fast radio bursts,” said Cornell’s Chatterjee.
Plotting an outburst is also a welcome surprise and a major discovery, he said.
“Nobody really believed we were going to be that lucky,” Chatterjee said. “To find one in our galaxy, it’s just the icing on the cake.”
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