You hear a lot about mysterious bursts of radio signals coming from distant parts of the universe. In our more fanciful moments, it’s easy to imagine them as errant little scraps of alien communication that somehow slipped through the cracks of space and landed here on Earth. They are usually nothing of the sort. More often than not, the explanation turns out to be some exotic but entirely natural astrophysical thing.

According to a new study published in the journal Nature Astronomy, astronomers may have finally found a crucial clue behind a particularly weird set of repeating radio signals known as long-period transients, a set of radio bursts that have been a real head-scratcher for scientists.

Mysterious Space Signals Have Puzzled Astronomers for Years. Now They Have Finally Found a Clue.

They’re called long-period transients because they repeat, but very slowly. Since 2022, astronomers have identified only about a dozen of them. Some emit bursts every few minutes or hours. Some have been pulsing for more than 30 years. Others disappear after only a few days. None of them seems especially interested in being consistent.

One of the most intriguing examples is a source called ASKAP J1745, first detected by Australia’s ASKAP radio telescope. To investigate it, researchers combined observations from radio, optical, and X-ray telescopes. While they did not find an explanation for all just yet, they may have found the Rosetta Stone, the decoder ring, that may one day help them figure out where these signals are coming from.

Scientists figured that long. Transients were just unusually slow pulsars, the spinning remnants of dead stars. A fine theory, but the problem is that pulsars shouldn’t behave that way. They spin too fast, and by the time they slow down enough to match these signals we’re getting, they should have stopped producing radio emissions altogether.

ASKAP J1745 seems to be a binary star system with a white dwarf that’s pulling material from its nearby companion star. When that material crashes onto the white dwarf, it creates X-rays. At the same time, superpowerful magnetic fields and streams of charged particles seem to be producing the radio bursts.

By observing ASKAP J1745 across multiple wavelengths of light, researchers say they finally have enough information to start translating the signals. It may be a while yet before the mystery is solved, but after years of gathering data that no one can make heads or tails of, astronomers finally have a credible lead on a space mystery that’s puzzled them for years.