Modern cosmologists use quantitative tools to obtain information about the evolution and structure of the universe. Modern cosmology dates back to the early 20th century, with the development of Albert Einstein’s theory of general relativity.
Now, researchers from the Atacama Cosmology Telescope (ACT) collaboration in northern Chile have published a series of papers presenting a groundbreaking new map of dark matter distributed over a quarter of the sky, extending deep into the cosmos, confirming Einstein’s theory of how massive structures grow and bend light over the 14 billion-year lifetime of the universe.
mapping dark matter
The new cosmic map uses light from the cosmic microwave background (CMB) as a backlight to outline the whole thing between us and the Big Bang. “It’s a bit like silhouetting, but instead of just having black in the silhouette, you have texture and clumps of dark matter, as if light were coming through a curtain of fabric that had lots of knots and bulges in it”said Suzanne Staggs, director of ACT.
80% of the universe is invisible
“This is amazing evidence that we understand the history of how the structure of our universe formed over billions of years, from just after the Big Bang to today.”, indicated Princeton physics professor Henry DeWolf Smyth. He added: “Amazingly, 80% of the mass in the universe is invisible. By mapping the distribution of dark matter in the sky at the greatest distances, our ACT lens measurements allow us to clearly see this unseen world.”
The distribution of dark matter
“Usually, astronomers can only measure light, so we see how galaxies are distributed in the universe; These observations reveal the distribution of mass, so they primarily show how dark matter is distributed throughout our universe.”said David Spergel, emeritus professor of astronomy at Princeton and president of the Simons Foundation. “We have mapped the invisible distribution of dark matter in the sky, and it is just as our theories predict”added co-author Blake Sherwin, a Princeton alumnus and professor of cosmology at the University of Cambridge, where he leads a large group of ACT researchers.
The difficulty of detecting dark matter
Even though it makes up most of the universe, dark matter has been hard 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 building and collecting data from the National Science Foundation’s Atacama Cosmology Telescope in the high Chilean Andes observed the light emanating after the cosmic dawn of the universe’s formation, the Big Bang, when the universe was only 380,000 years old. Cosmologists often refer to this diffuse CMB light that fills our entire universe as “fossil radiation.”
The ACT research team has been working on this project for over a decade, using data from multiple sources, including satellites, ground-based telescopes, and the latest instrument technology. The final map is a high-resolution view of the early universe, showing the tiny fluctuations in dark matter, helping scientists understand how galaxies formed.
“This map is a testament to the power of observations, theory and collaboration,” Devlin said. “This is a great achievement and an important milestone for our collaboration”he also noted.
The next step for the ACT team will be to use the map to better understand the physics behind the accelerating expansion of the universe, and also to look for evidence of cosmic inflation, a theory that describes how the universe went from being a subatomic particle to a vast one. cosmic structure in a fraction of a second after the Big Bang.
