The CHIME telescope has now used its own measurements to detect dark energy, seven years after the project started. This is the first time the instrument has produced such findings independently, without relying on verification from other observatories. Published Monday (Sept. 28) in The Astrophysical Journal, the results show the telescope’s capacity to chart the spread of hydrogen gas throughout the early cosmos, a function it was originally designed for.
Located near Penticton, British Columbia, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is an array of radio telescopes. It maps the entire northern sky on a daily basis. The design of CHIME was built to detect the faint radio signals given off by hydrogen, the very substance from which stars take shape, serving as a way to trace how matter is arranged throughout space.
For years, CHIME relied on outside telescopes to confirm its findings — a costly and slow undertaking. The new study, which took nearly a decade to produce, alters that arrangement. It is based on observations spanning 94 nights in 2019, all of which underwent careful review prior to release. The instrument can pick up radio emissions from as far back as 3 billion years after the Big Bang, a time when the cosmos was still a fraction of its present size.
The signal that held
The team pushed hard to rule out a false alarm, and the signal held up after every test, according to Arnab Chakraborty, a postdoctoral fellow at the University of Toronto who is a study co-author. He said in a statement that the effort required convincing themselves the result was real.
The potential rewards are significant. The authors say the telescope could provide researchers with a fresh, economical means to investigate dark energy, the little-understood force behind the universe’s accelerating expansion.
What hydrogen tells us
Chakraborty explained that hydrogen is the most plentiful element in the cosmos and serves as the building block for star formation. Because its faint radio signal functions as a marker, it shows where matter is spread throughout the universe.
The arrangement of those markers holds evidence of how the universe expanded at various points throughout its history. Tracing it might uncover fresh insights into why the cosmos grew more quickly with time, a mystery that has long troubled astronomers.
A decade of labor preceded the release of this paper, during which the team reviewed their findings with great care before putting them into print. The observations on which it rests span 94 nights in 2019, and the resulting measurement of dark energy is derived solely from CHIME’s own data.
The 2% finding
An accompanying paper published in The Astrophysical Journal includes more information about where hydrogen is found in the cosmos. This study suggests that about 2% of hydrogen is “neutrally atomic” — meaning the atoms contain a balance of just one proton and one electron, resulting in no overall electric charge — which is “broadly consistent” with measurements by other telescopes.
Shabbir Shaikh, who works as a postdoctoral fellow in the School of Earth and Space Exploration at Arizona State University and is a co-author on both papers, commented on the statement about the consistency with other telescopes.
A large team, including Amiri, Bandura, Cliche, Dobbs, Foreman, Gray, Halpern, Hill, Hinshaw, Höfer, Joseph, Kruger, Landecker, Van Lieshout, MacEachern, Masui, Mena-Parra, Miller, and Wulf, signed the papers. The full citation reads “Detection of the Cosmological 21 cm Signal in Autocorrelation at z ∼ 1 with the Canadian Hydrogen Intensity Mapping Experiment,” published in The Astrophysical Journal, 1009(2), 159, with a DOI of doi:10.3847/1538-4357/ae9835.
The path to independence
Prior to the new research, CHIME needed to double-check its own findings using other instruments. That precaution mattered because CHIME wanted to examine the universe’s ancient hydrogen gas with its own readings, standing apart as a separate standard that did not depend on outside telescopes.
The group argued that the instrument’s observations should be judged solely on their own merit, without needing confirmation from external sources. The fresh research demonstrates that this is possible.
What comes next
The researchers intend to examine CHIME’s remaining seven years of observations in order to collect additional data on their hydrogen gas research. Doing so would stretch the measurement of dark energy over a more extended period of time.
The telescope’s ability to measure dark energy on its own means future studies can move faster and cost less. The method relies on CHIME’s own instruments, not external confirmation.
Why dark energy matters
The universe is growing faster and faster, and the mysterious force driving that expansion is still not fully understood by scientists. Decades of study have failed to fully explain dark energy, though researchers keep looking for improved methods to measure it.
The telescope takes a novel route by following the spread of hydrogen across the early universe, letting scientists track how matter moved and how the expansion behaved at various points in cosmic history.
The 2% result on neutrally atomic hydrogen stands apart from the rest of the research. Shaikh pointed to its agreement with observations made by other telescopes in his remarks.
The long road to proof
It took seven years for the findings to be confirmed, but the potential reward is substantial. According to the researchers, the instrument could provide scientists with an inexpensive new means of investigating dark energy.
The team’s diligent effort proved successful. Once the testing was completed, the signal persisted.
What we know so far
- Live Science’s study was published Monday (Sept. 28) in The Astrophysical Journal
- It draws on observations made over 94 nights in 2019, carefully reviewed before publication
- The telescope detects radio signals as far back as 3 billion years after the Big Bang
- About 2% of hydrogen is neutrally atomic, broadly consistent with other telescopes
- The team plans to analyze CHIME’s other seven years of observations in future research
Seven years of testing and 94 nights of observations have culminated in a milestone result for CHIME: a telescope originally built to map ancient hydrogen has now demonstrated its ability to measure dark energy on its own.
The signal remained.
Source material: “CHIME telescope unlocks new way to study the universe's bafflign expansion,” Live Science.
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