A mysterious object in a galaxy 500 million light-years away is confusing scientists with its signals. It appears to be transmitting signals that reach Earth in a repeating, 16-day pattern, but researchers have no idea why.

According to a recent study, this marks the first time astronomers have detected a reliable pattern in the signals, known as fast radio bursts, or FRBs. It's an important step in figuring out where the bursts originate from.

Before now, such pulses appeared to be random in timing. That changed when the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB) discovered a repeating pattern.

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The recently detected FRB, known as FRB 180916.J0158+65, sends out bursts that last for four days before stopping for 12 days and then repeating. The first 28 cycles were observed between September 2018 and October 2019 using the CHIME radio telescope in British Columbia.

"We conclude that this is the first detected periodicity of any kind in an FRB source," the study's authors said. "The discovery of a 16.35-day periodicity in a repeating FRB source is an important clue to the nature of this object."

Scientists recently pinpointed this specific FRB to a spiral galaxy known as SDSS J015800.28+654253.0, located half a billion light-years from Earth — making it the closest FRB ever detected. Researchers hope that tracing the burst's origin will help them to determine what caused it.

The first FRB was spotted in 2007, and the signals have mystified scientists ever since. They only last for a thousandth of a second, making them difficult to study. Hundreds have been spotted, but only a handful have ever repeated themselves — and they seem to come from locations all over the universe.

While the cause of the repeating pattern is unknown, researchers said the FRB could be orbiting a black hole-like object, flashing its signal at a specific point in its orbital period.

According to another study looking at the same data, the pattern could be consistent with that of a binary star system containing a massive star and a dense neutron star. The neutron star could be emitting the bursts, which are sometimes hidden by winds caused by its massive friend.

"Fast radio bursts are exceedingly bright given their short duration and origin at great distances, and we haven't identified a possible natural source with any confidence," Avi Loeb, a Harvard-Smithsonian Center for Astrophysics theorist, said in a press release back in 2017.

There is one source most scientists have generally ruled out: aliens. But discovering more repeating FRBs may be the only way to know for sure.