Scientists Map Dark Matter in Unprecedented Detail Using James Webb Space Telescope
Using observations from the James Webb Space Telescope across a region of sky almost three times the size of the full moon, scientists have produced the most detailed cosmic map yet of dark matter. This mysterious substance accounts for most of the matter in the universe, yet remains invisible to telescopes and the human eye.
Ordinary matter forms stars, planets, people and everything that can be directly observed. However, it represents only about 15 percent of all matter in the cosmos. The remainder consists of dark matter, which neither emits nor reflects light and can only be detected through its gravitational influence.
Scientists infer the presence of dark matter by observing its large scale effects. These include the speed at which galaxies rotate, the way galaxy clusters remain bound together and the bending of light from distant objects as it travels through massive cosmic structures.
Light bending reveals hidden structure
The new map relies on a phenomenon known as gravitational lensing. As light from distant galaxies passes through regions filled with matter, including dark matter, it bends slightly. This process causes subtle distortions in the shapes of background galaxies. By analysing distortions in roughly 250,000 galaxies observed by Webb, researchers traced the distribution of matter along the line of sight.
An earlier dark matter map was produced using the Hubble Space Telescope. However, Webb’s superior sensitivity has doubled the resolution of the new map. It also covers a larger cosmic volume and looks much further back in time, reaching approximately eight to ten billion years ago, a crucial era for galaxy formation.
“This allows us to resolve finer dark matter structures, detect mass concentrations that were previously unseen, and extend dark matter mapping into earlier epochs of the universe,” said Diana Scognamiglio of NASA Jet Propulsion Laboratory, lead author of the study published in Nature Astronomy.
A sharper view of the cosmic web
The map reveals the cosmic web with unprecedented clarity. This vast structure consists of galaxy clusters, immense filaments of dark matter along which galaxies and gas are distributed, and regions where matter density is much lower.
Webb, an infrared telescope with around six times the light gathering power of Hubble, was launched in 2021 and became operational in 2022. According to Scognamiglio, the telescope effectively provides a far denser grid of background galaxies. As a result, sharper images directly translate into a sharper dark matter map.
Insights into galaxy formation
The mapped region is part of the Cosmic Evolution Survey, located in the direction of the constellation Sextans. Researchers say the dataset will support many future investigations into how the universe evolved.
A central question in astrophysics concerns how galaxies grow and change over time. According to Jacqueline McCleary of Northeastern University, dark matter halos act as the birthplaces of galaxies. Therefore, understanding where dark matter lies and how much exists provides crucial constraints for models of galaxy formation and evolution.
Support for the standard cosmological model
The gravitational lensing technique used in the study traces both dark and ordinary matter. Researchers said their findings align with the leading cosmological framework known as Lambda-CDM. This model describes a universe shaped by dark matter and dark energy since the Big Bang.
Within this framework, dark matter forms the gravitational backbone of the universe, shaping the large scale cosmic web. The new map offers the sharpest observational view yet of this hidden scaffolding.
With inputs from Reuters