New High-Definition Pictures of the Baby Universe
Physics Professor Colin Hill and collaborators have released the clearest images to-date of the universe in its infancy.
New research by the Atacama Cosmology Telescope (ACT) collaboration—a team of researchers that includes Columbia Physics Professor Colin Hill—has revealed the clearest images yet of the universe’s infancy, the earliest cosmic time accessible to humans. Measuring light that travelled for more than 13 billion years to reach a telescope high in the Chilean Andes, the new images reveal the universe when it was about 380,000 years old—the equivalent of hours-old baby photos of a now middle-aged cosmos.
“These pictures offer a vital glimpse of the universe before the earliest stars and galaxies formed,” said Hill. “They also help address major questions about apparent contradictions in the universe’s rate of expansion, confirming that our leading theories correctly describe the early universe.”
Since the universe is expanding, more high-powered telescopes allow researchers to see light from more distant parts of the universe that has taken many light-years to travel to Earth. In other words, a more powerful telescope allows us to see further back in time.
The new images of the early universe, which show both the intensity and polarization of the earliest light with unprecedented clarity, reveal the formation of ancient, consolidating clouds of hydrogen and helium that later developed into the first stars and galaxies. This background radiation is known as the cosmic microwave background.
The new results have also thoroughly tested and confirmed the standard model of cosmology, and have ruled out a majority of competing alternatives, the research team asserts. The standard model posits, among other things, that the universe was born 13.8 billion years ago, is dominated today by dark energy, and is expanding today at a rate known as the Hubble constant.
Professor Hill’s collaborators on the project were Kristen Surrao and Samuel Goldstein, both Columbia doctoral candidates in Physics; and Boris Bolliet, a former Columbia Physics postdoctoral researcher, and Aleksandra Kusiak, former Columbia Physics PhD student (GSAS’24), both of whom are now affiliated with Cambridge University.
The new pictures of the cosmic microwave background add higher definition to those observed more than a decade ago by the Planck space-based telescope.
The work has not yet gone through peer review, but the researchers are presenting their results at the American Physical Society annual meeting on March 19.
The Hubble Tension
Professor Hill and his group focused on analyzing the new data to search for ingredients in the cosmos, beyond the ones that researchers already know exist, like dark matter, normal matter, radiation, and dark energy.
If they had turned up evidence that the universe was made from more ingredients than just those that scientists now recognize, it would have affected the calculation of the Hubble constant, the rate at which the universe is expanding today.
That rate has been a point of disagreement among cosmologists in recent years, a dispute known as the Hubble tension. Measurements derived from the cosmic microwave background have consistently shown an expansion rate of 67–68 kilometers per second per megaparsec, while measurements derived from the movement of nearby galaxies indicate a Hubble constant as high as 73–74 km/s/Mpc.
Using their newly released data, the ACT team confirmed the lower value for the Hubble constant, with greater precision than ever before.
A major goal of the work was to investigate alternative models for the universe that would explain the disagreement. “We wanted to see if we could find a cosmological model that matched our data and also predicted a faster expansion rate,” said Hill, who is one of the lead authors. Alternates include changing the way neutrinos and the invisible dark matter behave, or adding a period of accelerated expansion in the early universe, or changing fundamental constants of nature.
“We have used the cosmic microwave background as a detector for new particles or fields in the early universe, exploring previously uncharted terrain,” Hill said. “The ACT data show no evidence of such new signals. With our new results, the standard model of cosmology has passed an extraordinarily precise test.”
Measuring the Universe’s Infancy
In the first several hundred thousand years after the Big Bang, the primordial plasma was so hot that light couldn’t propagate freely, making the universe effectively opaque. The cosmic microwave background represents the first stage in the universe's history that we can see—effectively, the universe’s baby picture.
The images give a remarkably clear view of very subtle variations in the density and velocity of the gases.
These detailed images of the newborn universe reveal answers to longstanding questions about the universe’s origins. “By looking back to that time, when things were much simpler, we can piece together the story of how our universe evolved to the rich and complex place we find ourselves in today,” said Jo Dunkley, Joseph Henry Professor of Physics and Astrophysical Sciences at Princeton University and the ACT analysis leader.
ACT’s new measurements have also refined estimates for the age of the universe and how fast it is growing today: The data confirm that the age of the universe is 13.8 billion years, with an uncertainty of only 0.1%.
The project is led by Princeton University and the University of Pennsylvania, with 160 collaborators at 65 institutions. This research was supported by the U.S. National Science Foundation, Princeton University, the University of Pennsylvania, and a Canada Foundation for Innovation award. The pre-peer review articles highlighted in this release are available online and will appear on the open-access arXiv.org.
This story was adapted from a press release by Princeton University.