One of the biggest astronomy discoveries of the last decade or so is the existence of fast radio bursts (FRBs), millisecond-long powerful emissions of energy that can be detected in radio waves. 

Among the most famous of these events is FRB 121102, the first FRB discovered to be repeating. This peculiar characteristic allowed researchers to track it back to its galaxy of origin and produce scenarios about its source.

Just a few months ago, researchers reported evidence that suggests FRB 121102 bursts are clustering in a periodic way. Now a new paper on ArXiv adds more observations to make the case even stronger. The system seems to be going through cycles that repeat every 161 days plus or minus five days.

The team believes the source of this FRB is a compact object with an intense magnetic field, such as a neutron star known as a magnetar. The fact that the source emits FRBs for about 100 days before not emitting anything for the following two months gave researchers the idea the magnetar is orbiting another object. This object might be another neutron star, a black hole, or a massive star.

In its 161-day orbit, the magnetar likely spends a large fraction of this time interacting with its companion and their shared environment. This interaction is probably how the FRBs are produced. For the remaining time, the magnetar is likely too far away for the interaction to take place. This scenario seems more and more likely as it's not the only FRB experiencing a period as FRB 180916 has an established period of 16 days.

A lot is still unknown regarding these events in general and FRB 121102 in particular. The emission in radio waves in a fraction of a second is equivalent to all the energy released by the Sun over three days. But these bursts are more than just radio waves. A singular simultaneous observation in X-rays suggests the burst could have an energy equivalent to what the Sun produces in 12 years.