There’s a sonic boom happening in space that’s four times faster than the speed of sound, all because two galaxy clusters slammed into each other.
arXiv · March 13, 2026 · 2603.12207
Why it matters
When two clusters of galaxies crash into each other, they create unfathomably large shockwaves. Astronomers found a 'Mach 3.9' shock, where the resulting X-ray blast is even more powerful and extensive than the radio signals it emits, representing one of the most violent events ever recorded in the universe.
From the abstract
We present spectral analysis results of deeper (270 ks) NuSTAR observations of the merging galaxy cluster system, ZWCL1856.8+6616, at redshift z=0.304, following a pilot study using shallower (30 ks) NuSTAR data (Tumer et al. 2024). The cluster hosts a double radio relic, pointing to a similar mass head-on collision at/near the plane of sky. We aim to find the relation between radio and X-ray shock features. Using data from both focal plane modules of NuSTAR, we study the temperature structure a