When two or more of the galaxy clusters collide, the hot gas in the interstellar medium slows down, but the galaxies, composed mostly of empty space, do not slow as fast.

The speed and direction of each of the clusters involved in the collision can thus be approximated through examining the offset between the galaxies and the gas.

The quick moving B exhibits kinetic Sunyaev-Zel'dovich effect (SZ effect for short), the first time this has been observed in an object, instead of statistically.

The B subcluster's kinetic SZ effect was discovered due to its lack of a thermal SZ effect, unlike the other three subclusters.

[5] MACS J0717 forms one of the largest known Einstein rings, with gravitational lensing distorting the light that reaches us from several adjacent phenomena.