Muon

A muon is an elementary particle, similar to an electron, which has a negative electric charge.

By the late 2250s, the N'shaii had developed a weapons technology which produced a muon burst and caused severe damage to an enemy starship. When the USS Constitution (NCC-1700) was first hit by the muon burst in 2257, the Federation had never encountered an alien race who had developed the technology. Eventually, Federation scientists eventually managed to find a defense against the muon beams.