Supernovae resulting from an impact by a large object moving close to the speed of light. Was used/popularized in a series called "Three Body Problem" as a weap

Supernovae resulting from an impact by a large object moving close to the speed of light. Was used/popularized in a series called "Three Body Problem" as a weapon (book premise is the "black forest theory", which is since every sentient civ is a potential existential threat advanced civs would genocide any aliens they detect, photoids being one of the exotic weapons to accomplish this).