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4w ago

CHIME Detects Faint 21 cm Hydrogen Glow at z ≈1 Using Only Its Own Data

The autonomous measurement opens a lower-cost route to trace cosmic expansion with hydrogen maps.

A view of CHIME at night, with the Milky Way in the background. Photo credit: CHIME collaboration.
Astronomers working with a unique radio telescope in British Columbia have achieved the most distant measurement to date that shows how hydrogen atoms are distributed in the deep universe.
The CHIME telescope, housed in British Columbia, Canada, was built in 2017 specifically to study how hydrogen, the most abundant substance in the universe, was distributed in the early universe | Wikimedia Commons

Overview

  • The CHIME Collaboration published papers in The Astrophysical Journal on Sept. 28–29 reporting the first autocorrelation detection of the cosmological 21 cm signal using only CHIME data.
  • Researchers extracted the signal from 94 clean observing nights chosen from roughly 2,000 days of archives and spent more than a year testing foreground, instrument and radio‑frequency interference removal to rule out false alarms.
  • The detected emission comes from about z ≈1, roughly eight billion light years away, and the team estimates about two percent of hydrogen was in neutral atomic form at that epoch.
  • By proving a standalone detection, CHIME reduces reliance on expensive optical galaxy surveys and creates a path to directly measure the universe’s expansion rate if analysis can recover spatial modes lost to foreground filtering.
  • CHIME teams in Canada, the U.S. and India plan to apply the same autocorrelation methods to nearly seven years of additional data to push to earlier times and refine constraints on dark energy while coping with growing local radio interference.