CHIME's First Standalone Signal Could Unlock Dark Energy's Secrets

There is a particular kind of mystery that hides in plain sight—something so vast and so pervasive that we cannot see it directly, only infer its presence from the way it shapes everything around it. Dark energy is such a mystery. It accounts for roughly 68 percent of the universe's matter-energy budget, driving the accelerating expansion of space itself, yet scientists still do not know what it is. Now, a faint glow from the distant universe, captured by a Canadian telescope, may offer a new way to investigate this elusive force.

The breakthrough comes from the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, a radio telescope near Penticton, British Columbia, that scans the entire northern sky every day. For the first time, researchers have shown that CHIME can detect the faint radio glow of hydrogen gas from the universe's deep past using only its own data—no cross-correlation with other telescopes required . The findings were published in The Astrophysical Journal.

Hydrogen is the most common element in the universe, the raw material from which stars form. Its faint radio emission acts like a cosmic tracer, revealing how matter is distributed across space . Previously, CHIME could map that distribution only by combining its observations with galaxy survey data from other instruments—operations that cost millions and focus only on regions dense enough to form stars. Now, by mapping the combined radio glow that hydrogen emits on its own, CHIME can explore the same questions at greater scale, further back in time, at a fraction of the cost .

The team used 94 nights of observation data collected in 2019 to detect a hydrogen signal from when the universe was about five billion years old. Their data indicate that roughly two percent of the hydrogen in the universe was in neutral atomic form at that time, broadly consistent with other measurements . The finding was not a sudden revelation. Researchers spent more than a year testing the signal to prove it was real. "We worked very hard to convince ourselves that this wasn't a false alarm," said Arnab Chakraborty of the University of Toronto, who first proposed the finding. "After all the tests, the signal remained" .

The significance of this work lies in what it enables. There are competing theories about the nature of dark energy, and CHIME can now investigate them independently. "This is a completely new technique for probing the cosmos," said Mark Halpern, CHIME's principal investigator at the University of British Columbia. "It's a bold new step in the global cosmology program and a Canadian success story" .

CHIME has now collected nearly seven years of data, and researchers are working to extend the analysis back to when the universe was only three billion years old . The faint glow of ancient hydrogen, it turns out, may be the key to understanding the force that governs the fate of everything.

AI Image Disclaimer: The visual elements in this article were generated using artificial intelligence for illustrative purposes only and do not depict the actual telescope or observations described.

Sources: UBC Science, Space.com, The Astrophysical Journal, PIB