The Bullet Cluster combines observations of hot gas with gravitational-lensing maps of mass. Their spatial separation after a collision provides strong evidence for matter not traced by the dominant visible gas. We rank this finding highly because independent observational methods test the same explanation. It does not identify a dark-matter particle or show dark matter glowing in a camera image; mapped mass is inferred from gravity’s effect on background light.

Source: Galaxy-cluster collisions strengthen dark-matter evidence.

Image credit: NASA's Scientific Visualization Studio - Marit Jentoft-Nilsen · Public domain. Resized and JPEG compressed.