EXPLAINER - Why scientists are puzzled by mysterious signals from deep space

For years, astronomers have been picking up strange bursts of energy from the cosmos — signals that last just milliseconds yet carry more power than the Sun releases in days. These puzzling flashes, known as fast radio bursts (FRBs), have become one of the greatest unsolved mysteries in astronomy.

What exactly are FRBs?

Fast radio bursts are ultra-bright pulses of radio waves that appear suddenly and then vanish. Some flare only once, while others repeat at irregular intervals.

The first FRB was detected in 2007 in archived telescope data from Australia. Since then, thousands more have been observed, but their origins remain elusive.

“It’s like someone is flicking a cosmic light switch on and off,” said Duncan Lorimer, the astrophysicist who first described the phenomenon. “But we don’t know who — or what — is behind it.”

Why are they so baffling?

• Enormous power

Each FRB unleashes as much energy in a fraction of a second as 500 million Suns. “The sheer intensity is staggering,” noted Harvard astronomer Avi Loeb. “Whatever produces them must be among the most powerful engines in the universe.”

• Mysterious sources

Pinpointing the origins is difficult. Some FRBs come from billions of light-years away, scattered across the universe. Theories include magnetars (super-magnetic neutron stars), collapsing stars, black holes colliding, and in the more speculative camp, even advanced alien technology.

• Repetition puzzles

While most bursts are one-offs, some repeat with odd rhythms. One discovered in 2020 emitted bursts every 16 days. “It’s like hearing a drumbeat from space,” said Kenzie Nimmo, an FRB researcher. “But the drummer is invisible.”

• Distorted on the journey

On their way to Earth, FRBs travel through cosmic gas, plasma and magnetic fields that bend and smear the signals. By the time they arrive, they’re so warped that tracing them back to their precise birthplace is almost impossible.

What do scientists know so far?

• Magnetars are the best lead. In 2020, a magnetar within the Milky Way emitted a burst that looked just like an FRB. “That was a eureka moment,” said Jason Hessels of the University of Amsterdam. “It showed us that magnetars really can do this.”
• Some bursts are tied to galaxies. Telescopes such as Canada’s CHIME have traced FRBs back to distant galaxies. “We can now say with confidence: these aren’t local,” said Chatterjee. “They’re happening across the cosmos.”
• They could help map the universe. Because FRBs are distorted as they pass through space, they carry information about the otherwise invisible matter between galaxies. “They are like cosmic X-rays,” said Victoria Kaspi, a leading FRB researcher. “They illuminate the skeleton of the universe.”

Why it matters

Solving the FRB mystery could open a new window into the universe. They could reveal the secrets of dark matter, measure how fast the universe is expanding, or uncover unknown forms of physics.

“Every time we think we’ve got it figured out, the universe throws us a curveball,” said Shami Chatterjee of Cornell University. “That’s what makes FRBs so exciting, they constantly defy expectations.”

The bottom line

Fast radio bursts are not proof of alien life, but they’re not fully explained by current science either. They sit in the tantalising gap between known physics and the unknown.

Whether they’re the work of collapsing stars, hyper-magnetised neutron stars, or something humanity has yet to imagine, FRBs remind us that the universe is still full of mysteries, and that sometimes, the cosmos whispers in bursts of static across the stars.

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