China's Sky Eye Reveals Stars Dance Behind Radio Bursts

For nearly two years, astronomers watched a cosmic mystery unfold 2.5 billion light years away, and what they found changes everything we thought we knew about the universe's most powerful radio flashes.

Fast radio bursts are millisecond flashes of radio waves so bright they can outshine entire galaxies. Scientists have been scratching their heads over these cosmic fireworks since discovering them, with most researchers assuming they came from isolated stars spinning alone in space.

But a team including researchers from The University of Hong Kong had a hunch something else was going on. Using China's Five-hundred-meter Aperture Spherical Telescope (nicknamed the "China Sky Eye"), they monitored a repeating burst source called FRB 220529A for 17 months.

At first, nothing unusual happened. Then in late 2023, the signal suddenly changed in a way that made the team's jaws drop.

The radio waves' polarization spiked by more than a hundred times before returning to normal over two weeks. It was exactly the signature you'd see if a burst of plasma from a nearby companion star had passed between Earth and the burst source.

"This finding provides a definitive clue to the origin of at least some repeating FRBs," said Professor Bing Zhang, Chair Professor of Astrophysics at HKU. The evidence points to a binary system containing a magnetar (a neutron star with an incredibly strong magnetic field) and a star similar to our sun, locked in an orbital dance.

The plasma clump that revealed the companion star's presence matches coronal mass ejections that our own sun regularly launches into space. While the companion star is too far away to photograph directly, its invisible hand left unmistakable fingerprints in the radio data.

The Bright Side

This discovery does more than solve one cosmic puzzle. It opens a window into how binary star systems work across the universe and suggests that many of these mysterious bursts might have hidden companions we haven't spotted yet.

The finding also supports a recent theory that all fast radio bursts come from magnetars, with binary interactions creating the perfect conditions for frequent, repeating bursts. If true, it means the universe's most dramatic light show is actually a cosmic duet.

The team's success came from patience and having access to the world's best radio telescopes. Continued monitoring of other repeating bursts may soon reveal just how common these stellar partnerships really are.

Sometimes the most profound discoveries come not from a single dramatic moment, but from watching and waiting for the universe to reveal its secrets.