The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has detected the faint radio glow of hydrogen gas from the distant universe using only its own observations, a first for the telescope. The signal, originating from about nine billion years ago, demonstrates a technique that could map cosmic structure and probe dark energy more cheaply than existing galaxy surveys.
The team analyzed 94 nights of data from 2019 and spent over a year testing the signal to rule out interference from human technology, cosmic noise, and the telescope itself. In an accompanying analysis, they found that roughly two percent of hydrogen at that epoch was in neutral atomic form, broadly consistent with previous measurements.
Because CHIME surveys the entire northern sky daily and has nearly seven years of data, researchers can now extend the method further back in time, aiming to study the universe when it was only three billion years old. The approach offers an independent way to test competing theories of dark energy without depending on more expensive galaxy surveys.