The Bullet Cluster is best known for being considered a “smoking gun” for the existence of dark matter, but even a famous galaxy cluster like this one has its secrets. For more than two decades, different measurements of the merging clusters’ dynamical mass ratio have yielded vastly different results. In a recent research article, Boseong Young Cho (Yonsei University) and collaborators used data from JWST and the Dark Energy Camera to revisit the Bullet Cluster and measure its mass ratio using new data. The image above shows a near-infrared view of the Bullet Cluster from JWST, with an overlay of mass contours derived from gravitational-lensing measurements. The team’s analysis assigned a mass of 1.5 quadrillion solar masses for the main cluster (on the left side of the image above), and a mass of 150 trillion solar masses for the subcluster. This suggests a mass ratio of roughly 10, which matches the value supported by hydrodynamical simulations and cements the event as a minor merger. The team also identified three distinct cluster halos (two in the main cluster and one in the subcluster), providing an important constraint on the cluster configuration for future modeling. To learn more about this investigation of the Bullet Cluster, be sure to check out the full research article linked below!
Citation
“Joint JWST–DECam Lensing Reveals that the Bullet Cluster Is a Minor Merger,” Boseong Young Cho et al 2026 ApJ 1005 28. doi:10.3847/1538-4357/ae6a90