8 billion-year-old radio signal reaches Earth

An artist's illustration traces the long, cosmic path of a fast radio burst that originated in distant galaxies and reached Earth 8 billion years later.

Astronomers have detected a mysterious blast of radio waves that have taken 8 billion years to reach Earth. The fast radio burst is one of the most distant and energetic ever observed.

Fast radio bursts, or FRBs, are intense, millisecond-long bursts of radio waves with unknown origins. The first FRB was discovered in 2007, and since then, hundreds of these quick, cosmic flashes have been detected coming from distant points across the universe.

The burst, named FRB 20220610A, lasted less than a millisecond, but in that fraction of a moment, it released the equivalent of our sun’s energetic emissions over the course of 30 years, according to a study published Thursday in the journal Science.

Many FRBs release super bright radio waves lasting only a few milliseconds at most before disappearing, which makes fast radio bursts difficult to observe.

Radio telescopes have helped astronomers trace these quick cosmic flashes, including the ASKAP array of radio telescopes, located on Wajarri Yamaji Country in Western Australia. Astronomers used ASKAP to detect the FRB in June 2022 and determine where it originated.

“Using ASKAP’s array of (radio) dishes, we were able to determine precisely where the burst came from,” said study coauthor Dr. Stuart Ryder, astronomer at Macquarie University in Australia, in a statement. “Then we used (the European Southern Observatory’s Very Large Telescope) in Chile to search for the source galaxy, finding it to be older and (farther) away than any other FRB source found to date and likely within a small group of merging galaxies.”

The research team traced the burst to what appears to be a group of two or three galaxies that are in the process of merging, interacting and forming new stars. This finding aligns with current theories that suggest fast radio bursts may come from magnetars, or highly energetic objects that result from the explosions of stars.

Scientists believe that fast radio bursts may be a unique method that can be used to “weigh” the universe by measuring the matter between galaxies that remains unaccounted for.

“If we count up the amount of normal matter in the Universe — the atoms that we are all made of — we find that more than half of what should be there today is missing,” said study coauthor Ryan Shannon, a professor at Swinburne University of Technology in Australia, in a statement. “We think that the missing matter is hiding in the space between galaxies, but it may just be so hot and diffuse that it’s impossible to see using normal techniques.”

So far, the results of current methods used to estimate the universe’s mass don’t agree with one another, which suggests the entire scope of the universe isn’t included

“Fast radio bursts sense this ionised material,” Shannon said. “Even in space that is nearly perfectly empty they can ‘see’ all the electrons, and that allows us to measure how much stuff is between the galaxies.”

This method of using fast radio bursts to detect missing matter was demonstrated by the late Australian astronomer Jean-Pierre Macquart in 2020.

“J-P showed that the (farther) away a fast radio burst is, the more diffuse gas it reveals between the galaxies. This is now known as the Macquart relation,” Ryder said. “Some recent fast radio bursts appeared to break this relationship.

Our measurements confirm the Macquart relation holds out to beyond half the known Universe.”

Nearly 50 fast radio bursts have been traced to date back to their origin points, and about half of them have been found using ASKAP.

“While we still don’t know what causes these massive bursts of energy, the paper confirms that fast radio bursts are common events in the cosmos and that we will be able to use them to detect matter between galaxies, and better understand the structure of the Universe,” Shannon said.

Astronomers said they hope that future radio telescopes, currently under construction in South Africa and Australia, will enable the detection of thousands more fast radio bursts at greater distances.

“The fact that FRBs are so common is also amazing,” Shannon said. “It shows how promising the field can be, because you’re not just going to do this for 30 bursts, you can do this for 30,000 bursts, make a new map of the structure of the universe, and use it to answer big questions about cosmology.”