Researchers from the Atacama Cosmology Telescope (ACT) collaboration have achieved a significant milestone by creating the most detailed map of dark matter distribution across a quarter of the entire sky, extending deep into the cosmos.
This groundbreaking view not only provides insights into the universe's evolution and structure but also confirms Einstein's theory of how massive structures grow and bend light over the universe's 14-billion-year lifespan.
The Atacama Cosmology Telescope
(Image Credit: M. Devlin, University of Pennsylvania via Wikimedia Commons)
Dark matter, which makes up 85% of the universe and influences its evolution, has been challenging to detect because it doesn't interact with light or other forms of electromagnetic radiation. As far as we know, dark matter only interacts with gravity.
To track it down, the more than 160 collaborators who have built and gathered data from the National Science Foundation's Atacama Cosmology Telescope in the high Chilean Andes observed light emanating following the dawn of the universe's formation, the Big Bang—when the universe was only 380,000 years old. This diffuse light that fills our entire universe is formally known as the cosmic microwave background radiation (CMB).
Suggested article: Is dark matter older than the big bang? (Universal-Sci)
Confirming Einstein's Theory and the Standard Model of Cosmology
The team tracks how the gravitational pull of large, heavy structures, including dark matter, warps the CMB on its 14-billion-year journey to us, like how a magnifying glass bends light as it passes through its lens.
Mathew Madhavacheril, assistant professor in the Department of Physics and Astronomy at the University of Pennsylvania, explained that the team made a new mass map using distortions of light left over from the Big Bang. Remarkably, it provides measurements that show that both the 'lumpiness' of the universe and the rate at which it is growing after 14 billion years of evolution are just what you'd expect from the standard model of cosmology based on Einstein's theory of gravity.
The innovative map employs the cosmic microwave background (CMB) light, functioning as a backlight, to outline all the matter that lies between us and the origins of the universe during the Big Bang.
Image Credit: ACT Collaboration
Addressing the "Crisis in Cosmology" Debate
The ACT's latest results have provided insights into an ongoing debate referred to as "The Crisis in Cosmology." This crisis stems from recent measurements that use a different background light, one emitted from stars in galaxies rather than the CMB. These measurements have produced results suggesting that the dark matter was not lumpy enough under the standard model of cosmology, leading to concerns that the model may be broken. However, the team's latest results from ACT were able to precisely assess that the vast lumps seen in this image are the exact right size.
Suzanne Staggs, director of ACT and Henry DeWolf Smyth Professor of Physics at Princeton University, noted that the CMB lensing data rivals more conventional surveys of the visible light from galaxies in their ability to trace the sum of what is out there. Together, the CMB lensing and the best optical surveys are clarifying the evolution of all the mass in the universe.
By using the cosmic microwave background (CMB) as a backlight, the map silhouettes all matter between us and the Big Bang, revealing the texture and lumps of dark matter.
Image Credit: Lucy Reading-Ikkanda, Simons Foundation
Future Observations and the Simons Observatory
Although the ACT operated for 15 years and was decommissioned in September 2022, more papers presenting results from the final set of observations are expected to be submitted soon.
The Simons Observatory will conduct future observations at the same site, with a new telescope slated to begin operations in 2024. This new instrument will be capable of mapping the sky almost 10 times faster than ACT, promising even more significant advancements and insights into the mysteries of the universe and the nature of dark matter.
Sources and further reading:
Is dark matter older than the big bang? (Universal-Sci)
Maybe Dark Matter is Warm, Not Cold (Universal-Sci)
Department of Applied Mathematics and Theoretical Physics (Cambridge University)
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