Scientists — with the help of antennae made from actual cake tins — have solved the mystery of what causes fast radio bursts that zip and zigzag through the universe.
They have known about these powerful energy pulses for about 13 years and have seen them coming from outside our galaxy, which makes it harder to trace them back to what’s causing them. Making it even harder is that they happen so fast, in a couple of milliseconds.
Then this April, a rare but much weaker burst coming from inside our own Milky Way galaxy was spotted by two dissimilar* telescopes: one a student’s set of handmade antennae, which included cake tins (in which you would cook a cake), the other a $28 million Canadian observatory.
They tracked that fast radio burst to a weird type of star called a magnetar that’s 32,000 light-years* from Earth, according to four studies in the journal Nature.
It was not only the first fast radio burst traced to a source, but the first coming from within our galaxy. Astronomers say there could be other sources for these bursts, but they are now sure about one source: magnetars.
WHAT IS A MAGNETAR?
Magnetars are incredibly dense neutron stars, with 1.5 times the mass of our Sun squeezed into a space the size of a city. They have enormous magnetic fields that buzz and crackle with energy. Sometimes flares of X-rays and radio waves burst from them, according to McGill University astrophysicist Ziggy Pleunis, a co-author of the Canadian study.
The magnetic field around these magnetars “is so strong any atoms nearby are torn apart and bizarre aspects of fundamental physics can be seen,” said astronomer Casey Law of the California Institute of Technology, who wasn’t part of the research.
There are maybe 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 doesn’t have as many star births as other galaxies, said Cornell University’s Shami Chatterjee, who wasn’t part of either research team.
FAST RADIO BURSTS
The burst from within our Milky Way, in less than a second, contained about the same amount of energy that our Sun produces in a month. And still that’s far weaker than the radio bursts detected coming from outside our galaxy, said doctoral* student and radio astronomer Christopher Bochenek of California Institute of Technology. He helped detect the burst with the handmade antennae.
These radio bursts aren’t dangerous to us, not even the more powerful ones from outside our galaxy, astronomers said.
The ones 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 University and part of the Canadian team.
Scientists think these are so frequent that they may happen more than 1000 times a day outside our galaxy. But finding them isn’t easy.
“You had to be looking at the right place at the right millisecond,” Prof Chatterjee said. “Unless you were very, very lucky, you’re not going to see one of these.”
Even though this is a frequent occurrence outside the Milky Way, astronomers have no idea how often these bursts happen inside our galaxy.
“We still don’t know how lucky we got,” Mr Bochenek said. “This could be a once-in-five-year thing or there could be a few events to happen each year.”
THE CAKE-TIN ANTENNAE
Mr Bochenek’s antennae cost about $21,000. Each is “the size of a large bucket. It’s a piece of 6-inch (15cm) metal pipe with two literal cake pans around it,” he said. They are crude instruments designed to look at a giant chunk of the sky — about a quarter of it — and see only the brightest of radio flashes.
Bochenek figured he had maybe a 1-in-10 chance of spotting a fast radio burst in a few years. But after one year, he struck it lucky.
The Canadian observatory in British Columbia is more focused and refined than Mr Mr Bochenek’s but is aimed at a much smaller chunk of the sky. It was able to pinpoint the source to the magnetar in the constellation Vulpecula.
WHY STUDY THE FAST RADIO BURSTS?
Because the bursts are affected by all the material they pass through in space, astronomers might be able to use them to better understand and map the invisible-to-us material between galaxies and “weigh” the universe, said Jason Hessels, chief astronomer for the Netherlands Institute for Radio Astronomy, who wasn’t part of the research.
Astronomers have had as many as 50 different theories for what causes these fast radio bursts, including aliens, and they emphasise that magnetars may not be the only answer, especially since there seem to be two types of fast radio bursts. Some, like the one spotted in April, happen only once, while others repeat themselves often.
Dr Michilli said his team has traced one outburst that happens every 16 days to a nearby galaxy and is getting close to pinpointing the source.
Some of these young magnetars are only a few decades old, “and that’s what gives them enough energy to produce repeating fast radio bursts,” Prof Chatterjee said.
Tracking even one outburst is a welcome surprise and an important finding, he said.
“No one really believed that we’d get so lucky,” Prof Chatterjee said. “To find one in our own galaxy, it just puts the cherry on top.”
- dissimilar: not similar
- light-years: unit of length or distance in space; equal to 9.46 trillion kilometres
- doctoral: describing a postgraduate university qualification called a PhD
- What is a fast radio burst?
- Where did the fast radio burst come from?
- What is Earth’s home galaxy called?
- What materials were used for the simpler antennae?
- What makes some of the magnetars able to produce repeating radio bursts?
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1. Ask the Scientist
Write five questions that you would like to ask the scientists in today’s story to find out more about magnetars, radio bursts, their research or anything else that you would like to know more about. What do you think their answers might be to each of your questions?
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Do you think that it was just luck that helped the scientists solve the mystery of what causes the radio bursts? Use information in the story and your own ideas to write a paragraph that explains your answer to this question.
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