The James Webb Space Telescope has produced the most detailed map ever assembled of the universe’s large-scale structure.
A team at the University of California, Riverside, published a catalog of 164,000 galaxies this week in The Astrophysical Journal — a dataset that lets scientists trace how the cosmos organized itself from when the universe was barely a billion years old to the present day.
The study is based on COSMOS-Web, the most extensive survey yet conducted with the telescope. The region of sky it covers is roughly the size of three full moons. Within that narrow window, Webb identified structures no other instrument had ever resolved in such detail.
But to appreciate what they found, it helps to understand what scientists were looking for.
The cosmic web is the vast hidden architecture that connects galaxies across space. It is made of filaments and sheets of dark matter and gas that border vast, nearly empty voids. Everything visible in the universe — planets, stars, galaxies — is embedded in that web like beads strung along an enormous net.
To map that structure is, in a sense, to map the skeleton of the universe. Until now, no instrument had been able to map it with sufficient resolution to reveal its finest details.
Why the James Webb Sees What the Hubble Could Not
The universe is expanding. As galaxies recede, the light they emit stretches. That stretching shifts the light into the infrared — the part of the spectrum invisible to the human eye. The older and more distant the galaxy, the more pronounced the shift.
The Hubble telescope was designed primarily to capture visible and ultraviolet light, which left the oldest, most distant galaxies largely beyond its reach.
Webb, by contrast, can detect extremely faint galaxies hidden behind clouds of cosmic dust, allowing researchers to look deeper into the early universe. Its mirror array also has seven times the light-collecting area of Hubble’s.
In practice, Webb identified far fainter galaxies within the same patch of sky and measured their distances with far greater precision. This made it possible to place each galaxy precisely in cosmic time, sharpening the map’s resolution.
When researchers compared the new data with earlier Hubble maps, they found something striking. Features that had appeared to be single structures turned out to be clusters of interconnected structures, revealing a far greater complexity within the cosmic web. What had looked like a diffuse smear was, in fact, a set of distinct filaments.
Professor Bahram Mobasher, who led the team at UC Riverside, said the improvement in depth and resolution was genuinely significant. It is now possible to observe the cosmic web as it appeared when the universe was only a few hundred million years old — an era that had previously been almost entirely out of reach.
A companion study led by Diana Scognamiglio of NASA’s Jet Propulsion Laboratory, published in Nature Astronomy in January 2026, used the same James Webb dataset to map dark matter through gravitational lensing.
The resulting map is twice as detailed as any dark matter map produced by other observatories. Together, the two studies offer, for the first time, a direct view of the invisible scaffolding on which the visible universe was built.
Open Data for Everyone
The team made the complete catalog of 164,000 galaxies publicly available, along with cosmic density measurements, the software used to build the map, and a video showing how the cosmic web evolved across billions of years.
Any researcher in the world can access and analyze the data — potentially leading to discoveries the original team never anticipated.
The study was led by Hossein Hatamnia, a graduate student at UC Riverside and the Carnegie Observatories, with contributions from scientists in the United States, Denmark, Chile, France, Finland, Switzerland, Japan, China, Germany, and Italy.
Webb has been in orbit since 2021 and has been conducting science operations since 2022. In that time, it has transformed our understanding of the oldest galaxies, star formation, and the large-scale structure of the cosmos. This map is its most ambitious undertaking yet.
And it is only the beginning. The data also provides, for the first time, a statistically robust foundation for studying how a galaxy’s position within the web — whether it sits in a void, along a filament, or inside a dense cluster — shapes its evolution over time.
The question of why galaxies are the way they are may finally be getting an answer, shedding light on a cosmos that also inspires astrophotographers to pursue the Milky Way double arch.
