New Delhi: Scientists from the Raman Research Institute in Bengaluru have detected the first signs of hydrogen from when the universe was just five billion years old.
According to a new paper published in The Astrophysical Journal on 28 September, a joint project between Canadian, American and Indian scientists used the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope to make the first ‘standalone’ detection of hydrogen glow during the early days of the 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.
The paper marks a new milestone for detecting the ancient hydrogen gas entirely on its own, in a method known as autocorrelation. Other radio telescopes like the MeerKAT in South Africa or the FAST in China usually detect ancient hydrogen plumes by cross-correlating, using existing maps of galaxies where they know hydrogen’s radio signals would be present.
However, the Indian and Canadian scientists detected hydrogen purely using CHIME’s own radio data, with observations across 94 nights, proving CHIME’s ability to not rely on external galaxy surveys to probe large-scale structures.
This methodology is directly relevant because CHIME’s detection of ancient hydrogen gas from seven to nine billion years ago paves the way for the study of dark energy and how the universe’s expansion is accelerating.
In a press release, Arnab Chakraborty, a postdoctoral fellow at the University of Toronto who first proposed the finding, explained how hydrogen can help understand the larger universe’s functioning.
“Hydrogen is the most common element in the universe and the raw material from which stars form,” said Chakraborty, who is also the co-author of the study. “Its faint radio emission acts like a cosmic tracer, revealing how matter is distributed across space.”
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‘CHIME scans a large fraction of cosmos’
Dark energy is an ‘unknown’ force that scientists say is responsible for the universe’s expansion at an accelerating rate, and covers approximately 70 per cent of the universe. While the universe’s expansion was confirmed in the 1920s, dark energy as a concept and a phrase was not coined until the 1990s. Yet there is little confirmation on whether it is a force, how it acts, and whether it is a ‘vacuum energy’ that acts opposite to gravity and produces outward pressure on the universe.
Meanwhile, the CHIME scientists in their paper explained how, despite there being multiple theories about the origin and meaning of dark energy in the world, CHIME can provide new insights into the debate by using its original findings.
“CHIME is a unique instrument that scans a large fraction of the cosmos as the sky drifts over it. With no moving parts and high-accuracy measurements, CHIME delivers a snapshot of what our sky looks like at radio wavelengths every day,” added co-author Dr Saurabh Singh, associate professor at RRI, in a press release.
Hydrogen acts as a map for the expansion process, or the ripples in the universe, and by detecting the initial signs of this element, the new paper provides a method to detect other factors of the universe’s expansion. To understand dark energy and its presence during the early days of the universe, the CHIME telescope can prove to be an important tool.
The paper said the researchers have nearly seven years of CHIME observations available and are working to expand the analysis to include earlier periods in cosmic history when the universe was only three billion years old.
(Edited by Saptak Datta)