Since its release in 2021, it is unraveling some of the universe’s most shocking mysteries. It has shown us giant planets at incredible resolution, and it has presented us with . Today, Monday adds a new achievement: the most detailed map ever obtained of the , that enigmatic substance that constitutes 85% of all the matter in the cosmos, but does not emit light. The cartography, published this Monday in , reveals not only the massive conglomerates of galaxies, but also the thin ones pipes of dark matter that connect them and the empty regions between them.
An international team led by , a researcher at NASA’s JPL (Jet Propulsion Laboratory) in Pasadena (USA), used observations of the James Webb on the COSMOS field, a region of the universe that has been exhaustively studied for decades. The map has more than double the precision of previous ones generated with the telescope Hubble.
It is the most abundant substance in the universe and, paradoxically, the most mysterious. It makes up approximately 85% of all matter that exists, but it does not emit or absorb light and does not interact with electromagnetic radiation. That’s why it is dark: We cannot see it directly with conventional telescopes. Astronomers can only detect it indirectly, through its gravitational effect on visible matter—stars, galaxies, gas and dust—and on light traveling through the universe.
What we know is that dark matter forms a kind of gravitational scaffoldingl invisible that supports the entire structure of the cosmos: without it, galaxies could not form, stars would not remain in their orbits and the universe would be radically different. Despite decades of research, scientists still don’t know what exactly it is. Mapping its distribution in detail, as the James Webbis crucial to understanding how the universe was born, evolved and continues to transform.
The technical feat of the study published this Monday is considerable. The team measured the shapes of 129 galaxies using a phenomenon known as weak gravitational lensing. When light from distant galaxies travels toward Earth, it passes through intervening dark matter, which bends its paths slightly. By measuring these tiny deviations, scientists can map the distribution of all matter, both visible and invisible.
“What makes our map special is that it detects structures at greater cosmic distances than was previously possible,” Scognamiglio explains to this newspaper. He James Webb It reveals more distant and faint forms of galaxies than its predecessors, allowing these lenses to reach times when the universe was just 4 billion years old.
The map published this Monday recovers 15 already known galaxy clusters that were previously detected. But it discovers new structures and opens a window into the young universe. During the era known as “cosmic noon”—when the universe was between 3 billion and 5 billion years old—the largest star formation in all of cosmic history occurred. The structures that James Webb detected at that time are, in many cases, systems in formation that do not yet contain enough hot gas to shine with other systems, such as X-rays.
The map also reveals what cosmologists call the “cosmic skeleton”: thin filaments of dark matter that connect large clusters to each other, outlining a three-dimensional network across space. “These results confirm the predictions of the current cosmological model (ΛCDM) and offer a powerful tool to study how the distribution of dark matter in the universe has shaped the formation of galaxies and the large-scale structure of the cosmos,” says Alberto Casas, a researcher at the Institute of Theoretical Physics (CSIC-UAM), in Madrid, who was not involved in the study. “This contribution possibly marks the beginning of a new era in precision cosmic mapping, which will allow us to more effectively test various theories about the nature of dark matter, a fundamental unsolved mystery,” he adds.
Scognamiglio is already working on the next step: three-dimensional reconstructions that not only show where the structures are, but when they formed. “The real revolution will come when we combine these dark matter maps with the detailed histories of star formation in COSMOS,” he emphasizes. “We will be able to connect how dark matter, gas and galaxies grow together during cosmic noon.”
Future missions like the telescope Nancy Grace Roman NASA and the probe Euclid of the European Space Agency will apply these techniques to much larger volumes of the universe, mapping the cosmic web at unprecedented scales.
