A Rarity in the Universe: MACSJ0717

The most energetic events in the Universe since the Big Bang have been the merging of 2 galaxy clusters. In rare cases, such as with MACSJ0717, 4 subclusters have been observed to be undergoing a merger. This produces a complex merger structure with very hot (T > 20 keV) gas, only observed in clusters containing shocks with high Mach number shocks (M > 2) such as the Bullet Cluster and Abell 665. While Chandra measurements have been performed on this cluster, the constraints placed on this hot gas are inconclusive. NuSTAR's ability to probe into the hard X-ray band provides better constraints on this temperature, as well as an opportunity to constrain potential Inverse Compton (IC) scattering that may occur from the reacceleration of electrons by the shock front.