Researchers have discovered an extraordinary phenomenon in the universe – a burst of radio waves originating from a galaxy merger that occurred approximately 8 billion years ago. Dubbed a fast radio burst (FRB), this millisecond-long burst emitted an energy equivalent to the amount our sun produces in three decades. Using the Australian SKA Pathfinder and the European Southern Observatory’s Very Large Telescope, scientists were able to pinpoint the location of this event.
Despite decades of study, astrophysicists are still grappling to explain the enigma of FRBs. These bursts are brief pulses of radio-frequency electromagnetic radiation, lasting a fraction of a second, yet they outshine most other sources of radio waves in the universe. Interestingly, radio waves have the longest wavelengths in the electromagnetic spectrum.
“The radio waves in FRBs are akin to those used in microwave ovens. In fact, the energy released in this FRB is comparable to microwaving a bowl of popcorn twice the size of the sun,” explained Ryan Shannon, an astronomer from Swinburne University of Technology in Australia and co-leader of the study published in the journal Science.
At 8 billion years old, this newly detected FRB is the oldest known burst of its kind, surpassing the previous record holder from 5 billion years ago. Considering the universe is a staggering 13.8 billion years old, this FRB offers a glimpse into our distant cosmic past. “We now know that fast radio bursts have been around for more than half the age of the universe,” said Stuart Ryder, an astronomer from Macquarie University in Australia.
First discovered in 2007, FRBs are believed to originate from hyper-magnetized neutron stars known as magnetars. These remnants of massive stars possess a mass equivalent to our sun but are only the size of a small city. “To generate such extreme bursts, you need objects as extraordinary as magnetars, which are among the most extreme entities in the universe,” Shannon added.
Unlike other energetic events associated with stellar explosions or black holes tearing stars apart, FRBs exclusively release energy in the form of radio waves. Furthermore, their signals are incredibly short. According to Shannon, while there are more energetic occurrences in the universe, FRBs are distinctive due to their radio-wave emissions and signal duration.
Although it is estimated that over 100,000 FRBs occur somewhere in the universe each day, only a small fraction of them have been detected. Out of around 50 FRBs identified, including this one, researchers have only managed to trace them back to their source galaxy in a few cases. Shannon explains, “Galaxies in the distant universe have a different appearance compared to those nearby, lacking the characteristic spiral arms. Therefore, it was unclear whether what we observed was one galaxy with a few clumps or multiple merging galaxies.”
Besides the mystery surrounding FRBs, scientists believe that studying these bursts can assist in detecting and measuring the immense amount of matter that fills the space between galaxies. As the radio waves traverse the cosmos, they can signal the presence of the intergalactic plasma, a hot gas where atoms split into subatomic particles such as ions and electrons. This intergalactic plasma constitutes a significant portion of the normal matter in the universe, which includes the material that forms stars, planets, and even humans.
“For decades, scientists have been searching for this matter, characterizing it as ‘missing’ since its diffuse nature renders it almost invisible by conventional means,” said Shannon.
(Reporting by Will Dunham; Editing by Daniel Wallis)
