23 Dec 2024
Using the radio telescope at Westerbork, The Netherlands, astronomers have discovered two dozen of the unexplained Fast Radio Bursts. After zooming in on the signal of the distant bursts, the astronomers found a striking similarity to the radio flashes emitted by nearby, known neutron stars. The discovery is remarkable because these nearby neutron stars already produce more energy than anything achievable on Earth. The distant stars that emit the Fast Radio Bursts must somehow generate an astounding one billion times more energy than the nearby ones.
A few years ago astronomers discovered that the Universe is continuously being pierced by short but very bright flashes of radio light. These so-called Fast Radio Bursts, or FRBs, last only about 1 millisecond, but in that short time they produce more energy than Sun creates in a month. Astronomers are highly interested in how nature can produce such vast amounts of energy. Up to now, the record holders or power generation were neutron stars, the remnants of exploded stars in our local group of stars, the Milky Way. The gravity, density and radiation around such neutron stars already amounted to some of the most extreme environments known, and they can be seen out to distances of about 100,000 light years. The newly-found Fast Radio Bursts, however, shine a billion times more radiantly than neutron stars. That is so bright that they reach Earth from the distant Universe, far outside our Milky Way, after travelling up to a mind-blowing one billion light years.
After more than two years of observing, The Westerbork Synthesis Radio Telescope (WSRT) discovered 24 new FRBs, according to a study that appears today, 2025 Jan 23. Its lead author, Inés Pastor-Marazuela (ASTRON and UvA) explains: “We were able to study these bursts in an incredible level of detail. We find that their shape is very similar to what we see in young neutron stars”. The other characteristics of the mysterious bursts point in the same direction, says Pastor-Marazuela, currently an NWO Rubicon Fellow at University of Manchester: “The way the radio flashes were produced, and then modified as they traveled through space over billions of years, also agrees with a neutron star origin, making the conclusion even stronger”.
The astronomers were able to zoom in so deeply on the signals because the WSRT was upgraded with an experimental supercomputer, called ARTS, the Apertif Radio Transient System, specifically for studying FRBs. “We generally do not know when or where the next FRB will appear,” says research leader Joeri van Leeuwen (ASTRON), “so we have a vast computer constantly crunch through all radio signals from the sky.” The astronomers taught ARTS to look for bursts that are very short, very bright, and from very far away, because they expected those flashes to be the most extreme and interesting. When the supercomputer finds such bursts, it autonomously zooms in on the data and informs the astronomers. Van Leeuwen: “After a while the resemblance with the flashes we know from highly magnetic neutron stars started to emerge, and we were very excited that we lifted part of the veil around these perplexing bursts.”
“We were just starting to think we were getting close to understanding how regular neutron stars can shine so exceedingly bright in radio”, says van Leeuwen. “But then the Universe comes along and makes the puzzle one billion times harder. That’s just great”. Even with this new enigma emerging, the team is excited that they have been able solve the riddle of the nature of FRBs, by now linking them to young neutron stars. Pastor-Marazuela: “It is amazing to work on these distant FRBs, really feel you are studying them up close from a single burst, and find they appear to be neutron stars.”
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Highly detailed observations of two dozen Fast Radio Bursts discovered by the Westerbork telescope showed the flashes were likely emitted by young, magnetized and highly energetic neutron stars, as illustrated here.