Astronomers have been puzzling over so-called fast radio bursts for several years now, but their unpredictable nature has hampered our attempts to understand this bizarre phenomenon. That’s why an object called FRB 121102 has been of such interest. Whatever this object is, it fires off fast radio bursts repeatedly. A team of astronomers studying the signals from FRB 121102 have now reported some unexpected results. The signals from FRB 121102 appear to be “twisted” in a way that indicates an extreme stellar environment.
The first fast radio bursts were identified in 2007, but they’ve been difficult to study. They were named accurately, you see. A fast radio burst lasts only a millisecond, and they don’t repeat. However, FRB 121102, which lies in the heart of a dwarf galaxy some 3 billion light years away, is the exception that proves the rule. This object emits fast radio bursts in clusters, allowing scientists to gather data in real time and train more instruments on the source.
We already know that fast radio bursts are incredibly energetic — they’d have to be for us to detect them so far away. These emissions could be related to supernovas, pulsars (rotating neutron stars), or magnetars (pulsars with powerful magnetic fields). FRB 121102 gives scientists an opportunity to learn more about the environment surrounding the radio source, which could help us understand what causes fast radio bursts. What they found is evidence of an extremely powerful magnetic field.
The team used the Arecibo Observatory (above) in Puerto Rico and the Green Bank Telescope in West Virginia to observe FRB 121102 as it let off a burst. The idea was to measure the polarization (geometric orientation) of the electromagnetic signal, which can be affected by local phenomena. The extraordinary polarization of light from FRB 121102 was totally unexpected. Polarization has been observed in other fast radio bursts, but this was 500 times more extreme.
There was a feeling among researchers that they were close to understanding FRB 121102, but now things are less clear. The new data points to several possible explanations, though. FRB 121102 may be a pulsar in close proximity to a growing supermassive black hole. The plasma spinning around the black hole could lens and polarize the light from FRB 121102, but why would a giant black hole be in a dwarf galaxy. Another possibility is FRB 121102 resides within a dense nebula that affects its signal, but then how did it get bright enough for us to see?
There’s plenty of work still to be done before we understand fast radio bursts. They’re hard to catch, but about 10,000 of them appear in the sky every night. Each one gets us a little closer to the solution.
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