There are at least 50 different theories regarding what fast radio bursts, or FRBs, actually are. A whole wiki is dedicated to the subject called the FRB Theory Wiki, which lists them out.
First discovered in 2007, astronomers and astrophysicists still don’t fully understand the true nature of these mysterious bursts. They last only milliseconds in duration, but their signals light up detectors with a brightness that, in one case, Nature described as similar to “the power of 500 million Suns.”
These powerful radio pulses shoot out across space randomly and from seemingly everywhere. But what’s causing them?
The answer to that question is, simply put, unknown, and it’s possible the origin of each fast radio burst is entirely different. That’s where all those theories come in. Some of the highlights, outside of the more ordinary explanations like objects orbiting a star, include starquakes, extragalactic alien light sails, and even white holes.
But, as I said, we just don’t know. Each FRB could be an ordinary natural phenomenon, or it could be a sign of the existence of an intelligent extraterrestrial civilization. That second possibility might sound like a joke, but you just never know: The nature of some FRBs does make you wonder.
While the majority of fast radio bursts are one-off events, the most perplexing are the ones that repeat. Only 10 are known to do so. However, in the news this week is FRB 180916.J0158+65, which not only repeats, but appears to follow a repeating 16-day pattern.
According to Phys.org, this is the “first instance of a repeating FRB, which repeats in a steady cycle.” It was detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB) from September 16, 2018 to October 30, 2019 (read the whole study over at arXiv).
“The FRB signals were observed to arrive approximately once an hour for four days and then suddenly cease—only to start up again 12 days later.”
As for the origin of this repeating signal, it could be anything from the aforementioned celestial body orbiting a star, as Phys.org suggests, to even a curious result of stellar winds moving in front of whatever might be causing the bursts, resulting in a predictable pattern.
Or, if we want to dream big, the FRB could be some kind of giant extragalactic lighthouse, a message sent across the cosmos saying “We’re here!” Or was it “Stay away”?
We should probably make sure before we go poking around too much.
Whatever the case, astronomers have successfully determined that FRB 180916 is located in a spiral galaxy 500 million light-years away. Notably, this is only the second fast radio burst astronomers have been able to map to a specific galaxy. FRB 121102, roughly 3 billion light-years away, is the other.
Of course, knowing the host galaxy of the FRB still doesn’t tell us what’s causing it, but it does get us closer to finding out.