A Signal From Billions of Light-Years Away Has Been Pulsing Like a Heartbeat — Exactly Every 16 Days. Scientists Are Still Arguing About What's Sending It.

It lasts one millisecond. Then it's gone.

In that single millisecond, whatever fired it released more energy than our Sun produces in three days. The burst travels for billions of years across the universe — and then it hits our radio telescopes, almost too fast to catch.

We call them Fast Radio Bursts. FRBs. And they might be the strangest thing humanity has ever detected.

We've known about them since 2007, when astronomer Duncan Lorimer found one hiding in archived telescope data — a signal recorded in 2001 that nobody noticed at the time. The Lorimer Burst. It came from somewhere outside our galaxy. It lasted a fraction of a second. It was brighter than anything we'd ever seen in radio waves.

Then it never came back.

Then one came back. Again and again. On a schedule.

In 2016, astronomers detected the first repeating FRB — FRB 20121102A, nicknamed "the Repeater." It came from a dwarf galaxy 3 billion light-years away. This was huge. If FRBs are one-off explosions, a repeater shouldn't exist. Something out there was firing bursts, surviving, and firing again.

Then came the one that makes scientists uncomfortable to talk about.

FRB 20180916B. It repeats. But it doesn't just repeat randomly. It fires in a 4-day active window — then goes quiet for 12.35 days. Then fires again. Then quiet. For years. Like clockwork.

Think about what that means. Something 500 million light-years away is pulsing on a schedule. You could literally predict when it fires next. Natural phenomena do have cycles — binary stars, rotating pulsars — but this rhythm is strange enough that astronomers published a paper titled: "No Simple Explanation."

Then we found one in our own backyard.

In April 2020, a magnetar inside our own Milky Way fired a burst. A magnetar is a dead neutron star with a magnetic field a quadrillion times stronger than Earth's. This one — SGR 1935+2115 — sits about 30,000 light-years away. Close enough to study in detail. And it produced something that looked, for the first time, unmistakably like an FRB from inside our own galaxy.

This was enormous. We'd caught the source in the act. The field shifts. The crust cracks. A burst of radio energy rips out at the speed of light. The magnetar hypothesis had its best evidence yet.

Then Avi Loeb said the quiet part out loud.

Harvard astronomer Avi Loeb — the same physicist who later argued Oumuamua might be artificial — co-authored a 2017 paper exploring whether FRBs could be consistent with alien technology. Specifically: a giant radio transmitter powerful enough to beam energy across the cosmos. A lighthouse sweeping the galaxy on a schedule, powering a spacecraft to near-light-speed.

Loeb was precise. He didn't say it was aliens. He said the energy output and geometry were mathematically consistent with a civilization operating at a scale we can barely imagine. He said the scientific process requires us not to rule things out without evidence.

Most mainstream astronomers disagree. The magnetar model fits the data better, they argue. Don't invoke aliens when a dead star explains it.

However — and this matters — no one has fully explained the 16-day cycle with magnetars. Proposed natural explanations include a companion star blocking the signal, orbital precession, or geometric wobble. None has been confirmed yet. The mystery is genuinely open science.

CHIME changed the game.

Canada's CHIME telescope started operating in 2018. It doesn't look like a telescope. It's a row of stationary, half-pipe shaped radio receivers covering an area the size of five hockey rinks, pointed at the sky 24 hours a day. It doesn't move. The Earth rotates and CHIME scans the sky as it turns.

Within its first year, CHIME found hundreds of FRBs. Before CHIME, we'd found roughly 100 total across a decade. Now we're cataloguing thousands. The universe, it turns out, is constantly crackling with these bursts. We just weren't listening carefully enough.

One of those repeaters — FRB 20200120E — was found shockingly close. Inside a globular cluster of the galaxy M81, just 11.7 million light-years away. In cosmic terms, practically next door. And its location inside a globular cluster — one of the oldest, densest star systems in existence — raises new questions about what kind of object could produce these bursts from that environment.

What comes next.

The Square Kilometre Array — a network of radio telescopes being built across South Africa and Australia — will be thousands of times more sensitive than anything we have today. When it comes online in the late 2020s, it's expected to detect thousands of FRBs per day. In real time. Not buried in archived data weeks later. Live.

We're about to go from glimpsing a mystery to watching it happen continuously. Whatever is out there firing these bursts — magnetar, cosmic accident, or something we haven't named yet — we're about to get a much cleaner look at it.

Maybe we'll finally crack the 16-day heartbeat. Maybe we'll catch a nearby burst close enough to image the source directly. Maybe the pattern will hold — regular, rhythmic, precise — and we'll have to think harder about what "natural" really means at scales this vast.

Or maybe we'll detect something the magnetar model flat-out can't explain.

For more on the universe's biggest unsolved signals, explore the SkyLens learning center. And if unexplained signals closer to home interest you, our UAP files cover 27 unresolved military cases released in May 2026. The live tracker shows everything we do know is up there — all 15,000 of them, in real time.