For the first time, scientists have detected a radio signal from outer space that repeats at regular intervals.

The series of so-called "fast radio bursts" – which are very short-lived pulses of radio waves that come from across the universe – were detected approximately once an hour for four days and then suddenly stopped, only to start up again 12 days later.

This cycle repeated every 16.35 days for over a year, according to a new paper about the research.

The bursts originated from a distant galaxy some 500 million light-years away.

"The discovery of a 16.35-day periodicity in a repeating FRB source is an important clue to the nature of this object," the scientists said in the paper.

The repeating pattern, reports Science X Network, "suggests the source could be a celestial body of some kind orbiting around a star or another body. In such a scenario, the signals would cease when they are obstructed by the other body.

"But that still does not explain how a celestial body could be sending out such signals on a regular basis," Space X said. "Another possibility is that stellar winds might be alternately boosting or blocking signals from a body behind them. Or it could be that the source is a celestial body that is rotating."

Alien signals? More bizarre 'fast radio bursts' detected from outer space

It's not likely to be aliens, the Massachusetts Institute of Technology said in a statement, because the signals are a sign of energetic events that are on the extreme scale of the cosmos. "Even a highly intelligent species would be very unlikely to produce energies like this. And there is no detectable pattern so far that would suggest there’s a sentient hand at play," MIT said.

Fast radio bursts last only a few milliseconds, making it difficult to accurately determine where they have come from.

"One of the greatest mysteries in astronomy right now is the origin of short, dramatic bursts of radio light seen across the universe, known as fast radio bursts or FRBs," said the Max Planck Institute for Radio Astronomy, in a statement.

"Although they last for only a thousandth of a second, there are now hundreds of records of these enigmatic sources," the Institute said.

Since 2007, according to MIT, most of the radio bursts are “one-offs” but a small amount are “repeaters” which recur in the same place.

The fast radio burst that repeats every 16 days was detected by the Canadian Hydrogen Intensity Mapping Experiment, a radio telescope designed and built by several groups of Canadian scientists to study outer space phenomena.