Representation of the magnetic fields of a magnetar and a radiation surge
McGill University graphic design team
For the first time, we’ve traced a strange explosion of radio waves – called a rapid burst of radio waves – back to its source in an attempt to solve a great cosmic mystery. The eruption came from a magnetar, a neutron star with a strong magnetic field.
Fast radio bursts (FRBs) are incredibly powerful flashes of radio waves that originate primarily from distant galaxies. Many explanations have been given for it since it was first discovered in 2007. However, because they tend to come from so far, there has never been enough evidence to determine what exactly made them up. Some FRBs have been traced back to their host galaxies, but their source has not been pinpointed.
In April, astronomers first found an FRB from our own galaxy that allowed them to take a closer look. Several teams of researchers examined the area where it formed and found that the eruption was from a magnetar called SGR 1935 + 2154. While magnetars have been a preferred contender for explaining FRBs, this is the first evidence that they can generate radio waves with energies high enough to explain the signals.
This outbreak, known as FRB 200428, is about 30,000 light years away from us, while the others we discovered were millions to billions of light years away. “It bridges the gap between the activity in our own galaxy and these strange events from many light years away,” says Brian Metzger of Columbia University in New York, who was not involved in this work.
The proximity of this outbreak made it appear extremely bright. “It’s much brighter than any other radio object in space,” says Bing Zhang of the University of Nevada in Las Vegas, one of the researchers who helped connect the FRB to its magnetic source.
The eruption had about three times the energy emitted by the sun every second and was far brighter than any radio wave ever seen by a magnetar, although it didn’t release quite as much energy as the FRBs outside our galaxy.
That may mean the other FRBs we’ve seen are created by more active magnetars that can give off more powerful explosions. “If all of the FRBs are made by magnetars, they can’t all be slow, old magnetars like this,” says Zhang. “Some must be young, that is, decades or centuries old, rather than thousands of years or tens of thousands.”
However, it is also possible that not all FRBs originate from magnetars. “When we talk about FRBs, we’re saying it’s an object, but they’re not objects, they’re bursts, and I think we can see those bursts from a whole host of other types of objects across the magnetars “, Says Amanda Weltman from the University of Cape Town in South Africa.
There has been evidence that there are different types of FRB: some seem to repeat and pop over and over, while others may only blink once. In addition, the few FRBs that have been traced back to their host galaxies appear to be in a variety of environments.
That single burst won’t allow us to answer the question of whether there are many types of objects that make up FRBs, but it can help us understand the essence of a type. “Even if these all come from magnetars, there are several different ways a magnetar can generate this radiation, and hopefully this will help us to mediate between them,” says Metzger.
Astronomers will watch the other known magnetars in our galaxy for more flares, Weltman says. “To see a rapid burst like this, your telescope needs to be looking in the right direction at the right time – there is no end to happiness,” she says. “This is just the beginning for FRB science. I think tens of thousands will be observed in different galaxies in a few years. “
Once we have a larger sample of FRBs and have a better grasp of the full breadth of their behavior, it becomes much easier to determine what creates them all and how. This discovery only solves part of the FRB puzzle, but it is a sign that we may soon be able to piece together the rest of the puzzle.
Journal reference: Nature, DOI: 10.1038 / s41586-020-2863-y
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