Scientists have used a powerful radio telescope in the interior of British Columbia, Canada to gain incredible new insights about one of the universe’s most perplexing and brilliant phenomena: Fast radio bursts (FRBs), which are unexplained signals from space. Sometimes they’re one-offs, and sometimes they mysteriously repeat in regular intervals, beating out a cosmic pattern.
The collaboration behind the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which scans the deep cosmos from the Okanagan region of BC, announced exciting new results during a press conference on Wednesday at the 238th American Astronomical Society. According to researchers, a new batch of FRB detections has for the first time correlated to the contours of the “cosmic web”; an unimaginably large structure connecting the universe that scientists are only starting to learn about.
First detected in 2007, these extremely brief and energetic pulses in space sometimes flare up once, sometimes repeat, and pop up all over the sky. Though they are clearly caused by powerful eruptions of some kind, hypotheses about their origins range from energetic supernovae, eruptions from dead stars, and even extraterrestrial intelligence. While dead stars called magnetars have become a particularly compelling candidate, the exact sources of FRBs remains unclear.
CHIME detected 535 FRBs during its first survey from 2018 and 2019, ushering in “a new phase of FRBs science,” said Kiyoshi Masui, assistant professor of physics at MIT during the collaboration’s AAS conference presentation. With this huge haul of bursts, CHIME singlehandedly quadrupled the number of FRBs found by all other telescopes before it began operations in 2017.
“This is the first large sample of FRBs discovered with a single survey, and all detected in the same way and all analyzed in the same way,” Masui said. “This will, for the first time, enable studies of the FRB population” which is “in contrast to studying individual specimens of FRBs,” he added.
The new survey includes the detection of 61 bursts traced back to 18 repeating FRB sources. Unlike the vast majority of FRBs, which appear for a millisecond flash and are never spotted again, repeaters emit several bursts from the same source, and they occasionally blast out signals in a periodic pattern. For instance, a burst detected by CHIME in 2018 operates on a cycle of 16 days in which flashes are clustered over four days followed by a dormant period of 12 days.
The CHIME team has demonstrated that the emission patterns of repeaters and one-off FRBs are different, suggesting that the two phenomena emerge from distinct astrophysical processes or orientations. For instance, the periodicity seen in some repeaters might be caused by the orbital motion of two extreme objects in a binary system, such as a black hole and neutron star, while one-offs could be produced by extreme objects in isolated systems.
The enormous new catalog of FRBs from CHIME has enabled the collaboration to map out the distribution of bursts across the whole sky, revealing that there’s no real preferential direction that contains more of them.
That said, FRBs do seem to align with a gigantic structure that connects the universe known as the cosmic web. This network is made of filaments and clusters of dark matter, a mysterious material that is abundant across the universe, and the sources of FRBs seem to fall within its general framework.
“It's long been theorized that if we had enough FRBs, we find that they're not perfectly uniform, but instead tend to trace out the large-scale structure in the universe,” said Alex Josephy, a graduate student at McGill University, during the conference. “These large structures make up the filaments of the cosmic web, and the scale here is truly immense.”
“For the first time, with this FRB catalog, we have detected this correlation between FRBs and largescale structures,” he added. “This is really, really exciting and ushers in a new era for FRB cosmology.”
To that point, one of the most exciting aspects of CHIME’s exciting survey of FRBs is not necessarily the bursts themselves, but how their patterns of dispersion—meaning how these signals travel across the cosmic medium—literally illuminates the universe as a whole.
CHIME’s results present “an opportunity to study the largescale structure of the universe, to use that record contained in the dispersion to map out where the matter is in the universe,” said Masui. “Not only are we going to learn much more about these fast radio bursts, but we're going to transition to this idea that we will use them as probes of the universe.”