The map shows how dark matter, an invisible material that cannot be seen directly, overlaps and intertwines with ordinary matter, the stuff that makes up stars, galaxies, and everything visible in space.
Published on Monday in Nature Astronomy, the research builds on earlier studies and provides new confirmation of how dark matter has influenced the universe on its largest scales, including massive galaxy clusters stretching millions of light-years across. These structures ultimately give rise to galaxies, stars, and even planets like Earth.
Lead author Diana Scognamiglio, an astrophysicist at NASA’s Jet Propulsion Laboratory in California, said the Webb telescope had delivered an unprecedented level of detail.
“This is the largest dark matter map we’ve made with Webb, and it’s twice as sharp as any produced by other observatories,” she said. “We used to see a blurry picture of dark matter. Now we’re seeing the invisible scaffolding of the universe in stunning detail.”
Although dark matter does not emit, reflect, or absorb light and passes through normal matter without interaction, it does exert a powerful gravitational pull. The new map shows this effect clearly, revealing a close alignment between dark matter and ordinary matter across vast regions of space.
Researchers said this alignment is not a coincidence, but the result of dark matter’s gravity drawing ordinary matter towards it over billions of years.
“Wherever we see a massive cluster of thousands of galaxies, we also see a similarly massive amount of dark matter in the same place,” said co-author Richard Massey, an astrophysicist at Durham University in the UK. “And when we see thin strings of galaxies connecting those clusters, we see the same structures in dark matter. They’ve grown together from the very beginning.”
The region mapped lies in the constellation Sextans and covers an area of sky about two-and-a-half times the size of the full moon. It forms part of the long-running Cosmic Evolution Survey (COSMOS), which has involved observations from at least 15 ground- and space-based telescopes around the world.
The first dark matter map of this region was produced in 2007 using data from the Hubble Space Telescope. Webb has now taken that work much further, spending around 255 hours observing the area and identifying nearly 800,000 galaxies, many for the first time.
Scientists inferred the presence of dark matter by studying how its gravity bends space, which in turn distorts the light from distant galaxies, a phenomenon known as gravitational lensing.
The new Webb map includes about 10 times more galaxies than previous ground-based maps and twice as many as those produced by Hubble. It reveals new concentrations of dark matter and shows known regions in far greater detail.
To improve distance measurements, the team also used Webb’s Mid-Infrared Instrument (MIRI), along with data from other telescopes. MIRI is especially useful for detecting galaxies hidden behind thick clouds of cosmic dust.
Scientists believe that in the early universe, dark matter clumped together first, creating gravitational wells that pulled in ordinary matter. This process triggered the formation of the first stars and galaxies and determined the large-scale structure of the universe.
By kick-starting star formation earlier than would otherwise have been possible, dark matter also played a role in creating the conditions needed for planets to form. Early stars forged heavy elements such as carbon, oxygen, and iron, which later became the building blocks of worlds like Earth.
“This map provides stronger evidence that without dark matter, we might not have the elements in our galaxy that allowed life to appear,” said co-author Jason Rhodes from NASA’s Jet Propulsion Laboratory. “We don’t experience dark matter in everyday life, but it has definitely shaped our existence.”
Looking ahead, scientists plan to use NASA’s upcoming Nancy Grace Roman Space Telescope to map dark matter across an area 4,400 times larger than the COSMOS region.
While Roman will cover far more of the sky, Webb will remain unmatched in terms of fine detail, with even more precise observations expected only from future telescopes such as NASA’s proposed Habitable Worlds Observatory.