Complex sentence: This framework of Physics helped Ken Bullough from Sheffield (UK), to realize that a small fraction of the comets he was studying were actually made of antimatter, since they were showing uncommon characteristics to distinguishing them from the greater part of comets.
Split into simpler sentences: This framework of Physics helped Ken Bullough from Sheffield (UK), to realize that a small fraction of the comets he was studying were actually made of antimatter. This particular group of comets was showing uncommon characteristics to distinguishing them from the greater part of comets.