Astronomers Combined 10,000 Images From the James Webb Telescope to Create the Largest Map of the Universe Yet. However, Something Doesn’t Match

Astronomers long believed the early universe was a dark place. They thought galaxies took time to form after the Big Bang. But the largest and deepest map of the universe, stretching back 13.5 billion years thanks to observations from the James Webb Space Telescope, just blew that idea out of the water..

Explore it yourself. COSMOS-Web is more than just a mosaic of images. It’s a detailed catalog of nearly 800,000 galaxies, covering 98% of the universe’s history in a specific region of the sky. This was made possible by Webb’s extraordinary sensitivity.

This gigantic panorama comes from more than 255 hours of observations by NASA, ESA, and CSA’s space telescope. The observatory focused on a region with few stars or gas clouds to block its view of the distant cosmos. The result: The widest contiguous image captured by Webb to date, composed of more than 10,000 individual exposures.

Comparisons. One way to understand the scale of this map is to compare it to the famous Hubble Ultra Deep Field—the most detailed visible-light image of the universe. If the Hubble Ultra Deep Field were the size of a printed page, COSMOS-Web would be a mural nearly 14 feet wide by 13 feet tall—with the same depth of detail.

Webb observes different wavelengths than Hubble—specifically near- and mid-infrared—but its instruments are so sensitive that it can detect 800,000 galaxies across 13.5 billion years in a region equivalent to three full moons in the night sky.

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Too much light, too soon. The big surprise isn’t the depth of these images—Webb was designed for that—but what they reveal about the early universe. Astronomers expected galaxies to be incredibly rare during the first 500 million years. Instead, they found roughly 10 times more galaxies than predicted.

“Since the telescope turned on, we’ve been wondering ‘Are these JWST datasets breaking the cosmological model?’” Caitlin Casey, leader of the COSMOS-Web project, said. “The big surprise is that with JWST, we see roughly 10 times more galaxies than expected at these incredible distances. We’re also seeing supermassive black holes that are not even visible with Hubble.”

International collaboration was essential. This monumental effort required a meticulous two-year process and global cooperation. The COSMOS team worked tirelessly to process raw data, align over 10,000 images and correct unexpected artifacts from the telescope. Thanks to their efforts, anyone can explore the map and make their own discoveries.

COSMOS-Web will continue expanding with new spectroscopic observations to analyze the internal chemistry of the most intriguing galaxies. The project’s primary targets include the “reionization era”—when light from the first stars cleared the cosmic fog—the evolution of massive galaxies, and the relationship between dark and visible matter.

Image | COSMOS-Web

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