Astrophysicists from The University of Hong Kong (HKU) have joined forces with a research team from Beijing Normal University (BNU) to develop a more accurate method for studying how a hypothetical form of dark matter—called "fuzzy" or ultralight dark matter—might affect the way light bends around massive objects in space. Their study is the first to use three-dimensional wave simulations of this type of dark matter to make gravitational-lensing predictions. Gravitational lensing occurs when a massive object, like a galaxy, bends the light from a more distant source, creating distorted or multiple images. The results, published in The Astrophysical Journal Letters, suggest that high-resolution observations of these lensed images could help scientists better understand the nature of dark matter. Dark matter is a mysterious substance that makes up about 85% of the matter in the universe. Unlike ordinary matter, it does not emit, absorb, or reflect light, so it cannot be directly observed. Instead, its existence is inferred from its gravitational effects on visible matter, such as the motion of galaxies and the bending of light. Dark matter is not part of the Standard Model of particle physics, the widely accepted theory that describes the fundamental particles and forces in the universe. In recent years, scientists have explored the possibility that dark matter might be composed of extremely light particles—so light that they behave like waves rather than particles. These ultralight particles could create interference patterns, much like waves on a beach, which might leave detectable traces in the multiple images of distant galaxies caused by gravitational lensing. This idea challenges traditional models of dark matter, which usually treat it as a collection of point-like particles. The research team, including Professor Jeremy Lim and Dr. Amruth Alfred from HKU, used direct computer simulations to model how ultralight dark matter might influence gravitational lensing. Their simulations produced predictions that closely matched the observed positions of lensed images from a well-studied quasar, outperforming traditional models. This suggests that gravitational lensing could serve as a powerful tool for testing theories about ultralight dark matter. The team is now exploring other potential effects, such as changes in the brightness of lensed images. The collaboration began with research visits by HKU scientists to BNU, where they worked closely with Professor Zong-Hong Zhu's group and doctoral student Jiajun Zhou, the lead author of the study. The team expressed excitement over the findings, believing they open new possibilities for studying dark matter through gravitational lensing.