Artist’s depiction of a magnetar, a possible source of FRBs. (Image: NASA)

First detected in 2002, Fast Radio Bursts (FRBs) are quick, high-energy pulses originating from galaxies billions of light years away. Scientists still don’t know the true nature of these bursts or what’s causing them, but new observations of the only known repeating FRBs are providing details about the extreme environments in which these pulses are born.
To date, astronomers have only documented a handful of FRBs; their fleeting, unpredictable appearances make observations difficult. A few years ago, however, scientists detected the only known source of repeating FRBs, an object dubbed FRB 121102. A new paper published today in Nature is now the first to provide a description of the environment in which this source is located. We still don’t know the nature of the source or cause of this repeating FRB, but the detection of an immensely powerful magnetic field in its vicinity suggests some tantalizing possibilities.

The 305-meter Arecibo telescope, in Puerto Rico, and its suspended support platform of radio receivers is shown amid a starry night. (Image: Danielle Futselaar/Brian P. Irwin/Dennis van de Water/Shutterstock)

Using the Arecibo Telescope in Puerto Rico and the Green Bank Telescope in West Virginia, an international team of astronomers led by Jason Hessels from the University of Amsterdam detected and monitored 16 recent bursts from FRB 1211012, which is located three billion light years from Earth in a nebula (a star-forming region) within a dwarf galaxy.
That’s an extreme distance, to say the least. Whatever’s causing these bursts must be releasing enormous amounts of energy with each pulse. Scientists estimate that there’s as much energy packed into a single millisecond of an FRB as our Sun releases over an entire day. Theories as to what’s causing FRBs include everything from magnetized neutron stars and supernovae through to supermassive black holes and the activities of extraterrestrial civilizations (yes, really).
What these researchers found was that these bursts are highly polarized, exhibiting a very high and variable Faraday rotation measure. When polarized waves travel through an area with a magnetic field, the polarization gets twisted by a phenomenon known as Faraday rotation. The stronger the magnetic field, the stronger the twisting. In the case of FRB 1211012, the twists are among the largest ever recorded in a radio source. This led the researchers to conclude that the pulses must be passing through an incredibly strong magnetic field in a dense plasma.
“This leads us to two hypotheses,” Hessels told Gizmodo, “The source is either a neutron star in an environment like [the one] at the center of our Milky Way galaxy, where there is a very massive black hole, or the source is in a dense, powerful, and highly magnetized nebula.”
Neutron stars are the remnants of ancient stars, between 10 to 29 times the size of our own Sun, that exploded in supernovae, where only the core remains. These stars aren’t capable of producing nuclear fusion reactions, so the absence of outward pressure causes the star to collapse in on itself, forming a small, super-dense orb. Neutron stars are so gravitationally heavy that they cause protons and electrons to combine into neutrons (hence their name).
Emily Petroff, an astronomer from the Netherlands Institute for Radio Astronomy who wasn’t involved with the new study, likes the new paper, telling Gizmodo that “the data and analysis are robust and the result has been confirmed with observations at multiple telescopes—that’s good enough for me.”
As for the possible source of the FRB, Petroff said it’s hard to say which scenario is responsible.
“I will say that putting the FRB source close to a black hole makes most sense based on what we already know in the Universe,” she said. “The black hole at the center of the Milky Way is the only place we’ve seen such strong fields, but just because we don’t have anything else similarly strong in our own galaxy (like a newborn magnetar in a dense nebula) doesn’t mean there can’t be other causes in other galaxies. Ultimately more observations are needed.”