It took 10 billion years for this signal from the early universe to reach us

Long before our solar system formed, a millisecond flash of light with a huge amount of energy erupted from a galaxy far, far away.

A study published in Science today captures the moment the flash, called FRB 20240304B, arrived on Earth 10 billion years later.

Study lead author Manisha Caleb, an astrophysicist at the University of Sydney, said this time frame was "insane", even for astronomers.

"If you put this in human perspective, when the light left the source, the Sun didn't exist, the solar system didn't exist, no humans existed," Dr Caleb said.

"Civilisation formed and we built radio telescopes and then we just happened to look at the right patch of sky at the right time."

The mysterious flash of radio energy, called a fast radio burst, is the oldest yet discovered and may help scientists understand more about the universe.

What are FRBs?

Fast radio bursts, or FRBs, are extremely high energy pulses of radio waves that almost always come from outside our galaxy.

The first FRB was found by an Australian team using the Parkes telescope in 2007.

Despite astronomers finding hundreds since then, Dr Caleb said we do not know what produces them.

"We know there are thousands of these events that go off in the sky every day," she said.

"And because they occur at radio wavelengths they are invisible to the human eye."

Lasting only a few milliseconds, they produce an immense amount of energy.

"In those few milliseconds, they emit as much energy as the Sun would over several days," she said.

Ryan Shannon, an astrophysicist from Swinburne University who has discovered other FRBs, said one potential source could be a magnetar, a neutron star with a powerful magnetic field.

"We found there's a magnetar in our own galaxy that emitted a pulse which looked like an FRB," Professor Shannon said.

"But I wouldn't rule out having more than one way to produce an FRB."

What is FRB 20240304B?

The newly discovered FRB was recorded in 2024 by the MeerKAT telescope in South Africa, which is reflected in its name.

"The B means it was the second FRB to be discovered that day," Dr Caleb said.

"I don't know who discovered the first one, but I like to think ours is way cooler."

The team's FRB had a very high "dispersion measure" (DM), meaning the light travelled a long way before being captured.

"Typically we find [FRBs with] a few hundred DM, or maybe even a thousand," Dr Caleb said.

"With about 2,400 units of DM we figured it had to be coming from really far away."

The team then used the James Webb Space Telescope to pinpoint where the FRB came from, homing in on a galaxy that existed just 3 billion years after the big bang.

"The galaxy itself was surprisingly small," Dr Caleb said.

"We didn't expect to find the FRB to be associated with such a puny little dwarf galaxy that's actively forming stars."

How can FRBs map the cosmic web?

Professor Shannon, who was not involved in the study, said the discovery "pushed the frontiers of FRBs".

"One of the big achievements was that this was an FRB that [they] could pinpoint its location on the sky," he said.

He also noted that dispersion from these far-flung FRBs could be useful to map the cosmic web.

This skeleton-like framework can tell us how the universe evolved.

"The majority of the normal matter in the universe, the stuff that Earth, you and I are made of … is spread out in the cosmic web," Professor Shannon said.

"We're able to use the FRBs now to study the cosmic web in ways that were impossible before."

Just even clocking this ancient flash was exciting.

"You've got this brief flash, lasting milliseconds, and here we are billions of years later lucky enough to catch it," he said.