On Feb. 7, 2024, the Trottier Space Institute hosted a public lecture on the mystery of Fast Radio Bursts (FRBs), fleeting blasts of cosmic energy that can outshine an entire galaxy, but only for a few milliseconds. They invited Duncan Lorimer, professor of Physics and Astronomy and Associate Dean for External Research Development at the Eberly College of Arts and Sciences at West Virginia University. He, along with his colleagues Maura McLaughlin and Matthew Bailes, first discovered FRBs in 2007. Thanks to this discovery, Lorimer’s team received the Shaw Prize in Astronomy in 2023.
In the field of astronomy, researchers observe the universe with a multitude of telescopes that detect light activity well beyond the visible spectrum perceptible by the human eye. Lorimer, for example, uses radio telescopes to detect and transform radio waves, a type of radiation that has the longest wavelength on the spectrum, into signals available for analysis.
Lorimer’s research on FRBs, which has been his focus for over 17 years, is part of a trend toward transient astronomy—the study of astronomical phenomena that exhibit a limited duration.
“[This is] when we talk about […] the universe changing on time scales of seconds or minutes, whereas traditionally we think about the universe just being ephemeral, remaining unchanged,” Lorimer said in the lecture.
According to Lorimer, he initially set off his work looking for pulsars, the spinning relics of large, fatally compressed stars after a supernova implosion. Along with many other radio astronomers, he was surveying for radio pulsars—a rapid pulsating signal picked up only by radio telescopes.
Subsequently, something strange happened: In an archival search of pulsar surveys, the researchers found an unexpected burst of energy from a 1.4-GHz survey of the Magellanic Clouds, recorded on Aug. 24, 2001, by the 64-metre diameter Parkes Radio Telescope, one of the largest single-dish radio telescopes in the southern hemisphere. The burst was unlike any consistent frequency they had collected. What’s more, after an additional 90 hours of observation, no further bursts occurred.
“We took account of the fact that the telescope was only seeing a small part of the sky, then extrapolated and said that hundreds of these events would be going off every day,” Lorimer said. “So, what we were basically saying was that there is a new class of [energy] sources that are out there in the cosmos, of which we’ve only found one.”
Based on the calculations Lorimer and his team performed, it is unlikely that this energy burst originated from inside the Milky Way.
“We came up to a staggering conclusion that this source was about three billion light years away, and we didn’t see a galaxy when we looked at that position in the sky,” Lorimer explained.
Fast forward to the year 2016, researchers finally found the first repeating source, a significant breakthrough moment since the initial discovery.
“Up until that point, we’d never seen one go off more than once. This source was suddenly starting to have these outbursts where we can see multiple pulses,” Lorimer said. “It wasn’t something like a gigantic explosion; it was something that was building up over time and then releasing energy before starting again.”
With time, the research team was able to obtain a direct distance measurement of these FRBs. The calculated distance was approximately 2.3 billion light years away, providing strong confirmation that the sources of FRBs are indeed situated beyond the Milky Way.
FRBs show amazing promise as probes of the large-scale structure of the universe and provide a new window into the population of compact objects located at vast distances.
“Through FRBs, we can start to carry out radio observations, sampling the electron content along gigantic lines of sight across the universe in a way that simply wasn’t possible in the past,” Lorimer concluded.
