The mystery FRB that came from nowhere baffles experts.

"Scientists using CHIME expected to find a young, energetic star behind a newly detected FRB. Instead, it came from a quiet, ancient galaxy where star formation ended billions of years ago. This challenges everything they thought they knew about FRBs. Credit: CHIME, edited"  (ScitechDaily, This Mysterious Radio Burst Came From Nowhere and It’s Baffling Experts)

"CHIME, pictured here, consists of four large antennas, each about the size and shape of a snowboarding half-pipe, and is designed with no moving parts. Rather than swiveling to focus on different parts of the sky, CHIME stares fixedly at the entire sky, looking for fast radio burst sources across the universe. Credit: CHIME Collaboration." (ScitechDaily, This Mysterious Radio Burst Came From Nowhere and It’s Baffling Experts)

The mysterious fast radio burst, FRB, seemed to come from nowhere. We can offer many explanations for that thing, including alien spacecraft. But it's more likely that something caused changes in some other wavelength. In some models, black holes can pull the X- or gamma-rays backward and they can stretch like you would pull a corrugated carpet. Things like gravitational or electromagnetic fields can act as lenses that focus the radio waves like lenses focus optical wavelengths. 

"The location of the fast radio burst, indicated by the oval outlines, is on the outskirts of a massive elliptical galaxy, the yellow oval at right. Credit: Gemini Observatory" (ScitechDaily, This Mysterious Radio Burst Came From Nowhere and It’s Baffling Experts)

The redshift (or Dooppler effect)  is one thing that can stretch radiation. Black holes and other very massive objects can cause virtual redshift. Or the neutron star or black hole that distances Earth can also stretch radiation. In that case is possible that GRB and XRB (Gamma- and X-ray bursts) can stretch into the radio waves.  Another thing that can change the radiation wavelength is the cosmic void. When a gamma ray or some other radiation hits a cosmic void that case can pull radiation forward. That can adjust its wavelength. 

Another thing. That can make the radio signals stronger than they were are gravitational or electromagnetic lenses. Changing the direction of the radio waves doesn't require a gravitational lens. Also,  plasma lenses or strong magnetic fields can focus radio waves. So can the plasma in the heliosphere turn the direction of the radio waves that they focus on the point of the planet Earth? 

Gravity lenses can also focus things like X- and gamma-rays. The gravity- or electromagnetic lens that focuses radio- or other types of radiation can turn the regular radio or other radiation to look very strong. Same way lenses can turn sunlight strong when they focus radiation at the same point. If that happens on the point of the radio or other telescope it amplifies the signal. But if astronomers want to register that thing.  That requires that the lens focus is just on Earth. 

https://scitechdaily.com/this-mysterious-radio-burst-came-from-nowhere-and-its-baffling-experts/