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Mysterious series of fast radio bursts may have been twisted by extreme environment

Amina Khan, Los Angeles Times on

Published in Science & Technology News

"We've seen this effect in other fast radio burst sources before, but in this case the effect is 500 times larger than what we've seen at other sources," Hessels said. "That was quite surprising."

These kinds of polarization effects, he added, can be seen around powerful phenomena such as the supermassive black holes at the center of galaxies. That makes some sense for FRB 121102, since the ionized gas, or plasma, around the black hole could be responsible for the magnetic field that's twisting the neutron star's signal.

The researchers think these repeated fast radio bursts are coming from a pulsar that happens to be sitting near a growing supermassive black hole that's surrounded by gas and dust. But there are other possibilities: Perhaps a pulsar is interacting with the nebula from a dead star to create the strange repeat signal.

There are problems with both of those ideas, Hessel pointed out. If the neutron star's radio signal is being twisted by the plasma around a nearby supermassive black hole, why would such a massive black hole exist in such a small dwarf galaxy? And if it's being affected by a surrounding nebula, how did it get to be so bright?

Even the idea that the source itself is some kind of pulsar doesn't explain why the bursts are so clumped. Spinning neutron stars have highly regular periods.

It could also be that plasma is acting as a sort of lens, focusing the radio light and allowing us to see it clearly. (In the black-hole scenario, the plasma could be both polarizing and lensing the radio waves, Hessel said.) That could mean that the other fast radio bursts are also repeats, and we just haven't had a proper space lens that would allow us to see more than one.

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Whatever its source, whatever its environment, and whether or not it is similar to the other one-shot fast radio bursts, understanding FRB 121102 will help astronomers to better understand the universe we live in, Hessels said.

After all, even though only a few dozen individual sources in total have been found, researchers estimate that perhaps 10,000 fast radio bursts flash across the night sky every single day. And just as a flashlight on a dark night can illuminate all the dust and fog particles in its beam, each of these radio bursts can reveal a little more of the contents of the space between the source and us.

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