Clearest images yet of the 380,000-year-old universe

The Atacama Cosmology Telescope (ACT) team has captured the clearest images of the universe in its earliest stages—when it was just 380,000 years old. Think of these as baby photos of a now middle-aged cosmos, taken by measuring light that traveled over 13 billion years to a telescope perched high in Chile’s Andes.

These groundbreaking images reveal the first steps towards forming stars and galaxies. What sets this study apart is its ability to show light and dark and the high-resolution polarization of light, offering incredible new details.

Suzanne Staggs, director of ACT, and Henry DeWolfDeWolf Smyth, Professor of Physics at Princeton University, said, “We are seeing the first steps towards making the earliest stars and galaxies. And we’re not just seeing light and dark; we’re seeing the polarization of light in high resolution. That is a defining factor distinguishing ACT.”

The new images of the cosmic microwave background (CMB) are sharper and more detailed than those captured over a decade ago by the Planck space telescope. Thanks to the Atacama Cosmology Telescope’s (ACT) five times higher resolution and improved sensitivity, researchers can now clearly observe faint polarization signals in the CMB, as noted by Sigurd Naess, a lead researcher from the University of Oslo.

These polarization patterns reveal how hydrogen and helium gases moved during the universe’s infancy. Previously, we could only see these gases’ locations, but now we can track their motions.

Suzanne Staggs compared it to using tides to infer the moon’s presence, as the movement of these gases tells us about the gravitational forces at play in different regions of early space. It’s an incredible leap in our understanding of how the cosmos evolved!

The new images offer the most transparent view of very subtle variations in the density and velocity of the gases that filled the young universe. What look like hazy clouds in the light’s intensity are more and less dense regions in a sea of hydrogen and helium—hills and valleys that extend millions of light years across. Over the following millions to billions of years, gravity pulled the denser gas regions inward to build stars and galaxies.

New images of the early universe are shedding light on its origins, helping scientists understand how it evolved into the rich and complex cosmos we see today. Jo Dunkley, a lead researcher from Princeton University, describes this as looking back to simpler times to understand our universe’s journey better.

Through these findings, researchers have measured the observable universe to extend nearly 50 billion light-years in all directions and hold the mass of around 1,900 “zetta-suns”—equivalent to 2 trillion trillion suns. Astonishingly, only 100 of these zetta-suns represent normal matter, the kind we can see and measure.

A further 500 zetta-suns worth of mass is mysterious dark matter. In comparison, the majority—about 1,300 zetta-suns—is attributed to vacuum energy, or dark energy, which dominates the universe’s vast emptiness.

The Atacama Cosmology Telescope (ACT) received funding from the National Science Foundation in 2004, with Lyman Page and David Spergel leading the project. Over the years, ACT has put the standard model of cosmology to its toughest tests yet, confirming its reliability without finding evidence of new physics.

The telescope’s results highlight the power of cosmic microwave background (CMB) measurements to explore the universe’s history, from its birth to massive stellar outbursts. Along the way, ACT also captured light from various cosmic objects, spanning our Milky Way, distant galaxies, black holes, and galaxy clusters—right back to the early universe.

After completing its observations in 2022, ACT has passed the baton to the more advanced Simons Observatory in Chile. ACT’s data is now available to the public through NASA’s LAMBDA archive, continuing to contribute to the study of our universe.

Journal Reference:

1. The CMB maps: Næss, Guan, Duivenvoorden, Hasselfield, Wang et al, 2025.
2. The CMB power spectra and fitting to LCDM: Louis, La Posta, Atkins, Jense et al, 2025.
3. Constraints on extensions to LCDM: Calabrese, Hill, Jense, La Posta, et al., 2025.