This Webb image didn’t merely capture galaxies; it shifted their position in the timeline.

A James Webb Space Telescope study is bringing new insight into the ages of some ancient galaxies, revealing that they are much older and more distant than previously believed. Webb, a collaborative observatory of NASA along with its European and Canadian partners, revisited a piece of the sky made famous by the Hubble Space Telescope’s ultra-deep field view over two decades ago. During that time, Hubble’s ambitious long-exposure image captured a seemingly starless area, yet it ultimately unveiled a tapestry of thousands of distant galaxies.

Now, with Webb’s advanced capabilities, this section of the sky continues to illuminate our understanding of the universe, offering fresh perspectives on the cosmic timeline. Known as the MIRI Deep Imaging Survey, this project utilized Webb’s mid-infrared instrument to detect light wavelengths that are invisible to our naked eyes. The new findings were shared in the journal Astronomy & Astrophysics.

With Webb, astronomers can observe the gentle infrared glow from ancient stars and the structures they have created. The telescope devoted 100 hours to the Hubble Ultra Deep Field area, including 41 hours focused on one specific filter. This remarkable effort captured faint signals from galaxies that emerged when the universe was only a few hundred million years old—a truly early phase in cosmic history.

To understand a deep field space image, consider it akin to a core sample taken from the ground; as you dig deeper, you uncover older rocks and soil. Similarly, this image is a tiny yet distant slice of space that reveals cosmic history by traversing billions of light-years, with each deeper layer representing an earlier time.

“To our knowledge, this constitutes the longest single-filter exposure obtained with Webb of an extragalactic field as of yet,” the authors shared. The project, affectionately known as MIDIS, identified nearly 2,500 light sources, with the majority being distant galaxies. Approximately 1,000 of these now have updated distance estimates based on the light shift observed.

Webb was designed to explore a significant period known as “cosmic dawn,” taking place between 100 million to 1 billion years after the Big Bang, and it captures light at those elusive infrared wavelengths. Notably, light gets stretched—or “redshifted”—over time due to the universe’s expansion. These infrared wavelengths also penetrate through gas and dust, allowing the telescope to unveil far-off, fainter light sources.

In one enlightening discovery, the project identified a galaxy previously thought to be 11.8 billion years old, which is now estimated to be closer to 13.3 billion years old, indicating its formation when the universe was perhaps just 450 million years old. This places the galaxy among the initial wave of galaxies formed. Other objects in the MIDIS image showcase a diverse array: hundreds of red galaxies, some bearing their hues due to dust or the presence of cooler, mature stars. This outcome highlights the potential of Webb’s MIRI instrument as a vital tool for uncovering ancient galaxies that may have been overlooked or misidentified in the past, surpassing the clarity achieved by NASA’s retired Spitzer infrared space telescope.

This encouraging progress inspires hope among researchers as they delve deeper into the evolution of the universe, tracing its journey from the dawn of the first galaxies to the period of peak star formation and supermassive black holes. “MIDIS surpasses preflight expectations,” the authors noted. “Deep MIRI imaging holds great promise for characterizing the galaxy population from cosmic noon to dawn.”