Starting in 2018, observations of galaxy clusters through the world's best telescopes have revealed unusual phenomena: short-lived fluctuations in brightness localized to compact regions within gravitationally lensed images. Here, I will show how the recent JWST observations of more than 40 transient events within a single gravitationally lensed arc, known as the Dragon Arc, can be used to probe the nature of Dark Matter (DM). These observations show a preferred spatial clustering inside rather than outside the cluster critical curve (a region where the magnification reaches the highest values). Our results show that pervasive density modulations predicted by ultra-light DM particles can create such an effect, while conventional ultra-massive DM particles predict the opposite effect. This finding follows on the wake of our previous work, featured on the front cover of Nature Astronomy, where we demonstrated that the three-decade long flux anomaly problem in lensing can be naturally resolved if DM is composed of ultra-light particles, providing independent support and pointing the path towards new physics.
I will also mention upcoming JWST Cycle 5 observations that we have successfully obtained to image lensed transients in galaxy clusters, and for the first time, in an individual galaxy known as the Cosmic Horseshoe.
Finally, I will briefly talk about our recent work on summarizing astrophysics research in 2025, uncovering various patterns and trends such as the astrophysical spectral fingerprint, publication costs and the global distribution of collaboration. These findings give a sense of the current state of affairs in the field, and will inform critical decisions on the future of Astrophysics. The paper can be found at: https://arxiv.org/abs/2602.12303
