Dark matter—the invisible scaffolding thought to hold galaxies together—is arguably the most elusive substance in the universe. Nearly a century of research hasn’t yet led to a confirmed direct detection, but scientists have learned to observe it indirectly. Now, one team has used those observations to produce the highest-resolution map of dark matter to date.

The researchers created the map, published Monday in the journal Nature Astronomy, by carefully measuring tiny changes in the shapes of hundreds of thousands of galaxies imaged by the James Webb Space Telescope. This allowed them to reconstruct the locations of mass—including dark matter—and map the invisible structure of the universe, lead author Diana Scognamiglio, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory, told Gizmodo in an email.

“We can’t see dark matter directly, so we map it by watching how it bends light,” Scognamiglio explained. “As light from very distant galaxies travels toward us, it is slightly distorted by the gravity of matter along the way.”

Dark matter as we’ve never “seen” it before

Astronomers believe ordinary matter—particles that interact with light and are therefore observable—makes up only one-sixth of all matter in the universe. The rest is dark matter, which does not emit or absorb light. It interacts with the universe only through gravity.

According to the standard model of cosmology, dark matter must exist in order for certain gravitational effects to make sense, such as the unexpectedly rapid rotation of galaxies or the fact that they’re held together more tightly than they should be. The best way for scientists to indirectly “see” dark matter is by measuring its gravitational effects.

Scognamiglio and her colleagues used weak gravitational lensing—the subtle distortion of light from distant galaxies caused by the gravity of intervening mass—to do exactly that.

High-resolution JWST images from the COSMOS-Web survey allowed the team to measure the shapes of 129 galaxies per square arcminute and reconstruct a matter map with an angular resolution of about 1 arcminute—more than twice the resolution of earlier Hubble Space Telescope maps.

“JWST gives us much sharper images and lets us see fainter, more distant galaxies than other telescopes, like Hubble,” Scognamiglio explained. “That means we have many more background galaxies to work with, and we can measure their shapes more precisely. More galaxies and sharper images translate directly into a sharper map.”

The map’s brightest regions mark places where large amounts of mass are concentrated, usually signaling massive galaxy clusters. The faint, thread-like features that connect these bright spots trace the vast filaments that link galaxies together, while darker, smoother regions show where relatively little matter exists.

“In simple terms, the map is a picture of the scaffolding of the universe,” Scognamiglio said.

A window into deep cosmic history

The exceptional resolution of this new map not only provides a highly-detailed view of the universe’s structure, it also allows astronomers to observe that structure much further back in time than previous maps have.

It traces dark matter back to the era when galaxies were forming most actively, and therefore provides a benchmark for tests of the nature of dark matter as well as models of the galaxy environment during peak cosmic star formation roughly 8 to 11 billion years ago.

“The map is consistent with our current cosmological model, which predicts that dark matter forms a web-like structure that galaxies grow within,” Scognamiglio said. “​​With this sharper view, we can test those predictions more precisely and look for small differences that could hint at new physics, such as alternative dark matter properties or subtle departures from standard gravity.”

She hopes that their map will pave the way for new research into how galaxies are influenced by their dark matter environments. “We can now investigate how star formation, galaxy growth, and quenching [the shutting-down of star formation] depend on where galaxies sit within filaments and clusters,” Scognamiglio explained.

The quality of the data also opens the door to studying how matter evolves over time, she added. This will aid Scognamiglio’s next project: producing three dimensional maps of the universe’s mass. Next-generation space telescopes such as NASA’s Nancy Grace Roman and the European Space Agency’s Euclid will support this work by producing high-resolution data that covers much larger areas of the sky.

“JWST shows us what is possible at ultra-high resolution, while those missions will scale this up to cosmic volumes,” Scognamiglio said.