Fast radio bursts (FRBs) are one of the least-understood events in the universe. They have been recorded fewer than 20 times since the first such occurrence was seen.

These events are so rare, some astronomers believed they did not exist. Now, researchers using the Arecibo Radio Telescope in Puerto Rico have seen an FRB sending out repeat bursts. Such an event has never been witnessed before.

Astronomers discovered the repeating FRB as they combed through Arecibo data from 2015, as the world's largest radio telescope surveyed the 17 known sites of fast radio bursts. Analysis suggests at least one of these targets, known as FRB 121102, emits a repeating signal. The most recently-recorded FRB was reported just a week before the announcement of the newly-announced phenomenon.

Some astronomers had previously suggested that the events responsible for the bursts could be cataclysmic explosions. This new analysis appears to contradict that theory.

"In our paper, we're showing that our FRB can't have an explosive origin. So, either there's an odd coincidence, or maybe there are different types of FRBs. Either way, it seems we've broken this enigmatic phenomenon wide open," Shami Chatterjee, a senior researcher at Cornell University, said.

These objects emit a series of energy bursts, with each pulse lasting around 1/100 second. This signal repeats thousands of times each day. Logically, if the events are repeating, then the process that produces FRBs must not destroy the star or body at the epicenter of the energy discharge.

Astronomers are still debating what causes fast radio bursts. However, their sources appear to be far out in space, suggesting the events are extremely powerful, to account for the amount of energy reaching us here on Earth. One popular theory is that neutron stars in other galaxies are at the center of FRBs. These stellar corpses are so dense, a single thimbleful of their material would contain more mass than Mount Everest.

Oddly, every FRB ever seen before 121102 was first recorded by astronomers utilizing the Parkes Observatory in Australia. That instrument allows researchers to see a good deal of the sky at a single time. Arecibo is designed for more detailed analysis.

Discovery of the repeating fast radio burst(s) was profiled in the journal Nature.