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A kugelblitz (German: [ˈkuːɡl̩ˌblɪt͡s] ⓘ) is a theoretical astrophysical object predicted by general relativity. It is a concentration of heat, light, or radiation so intense that its energy forms an event horizon and becomes self-trapped. In other words, if enough radiation is aimed into a region of space, the concentration of energy can warp spacetime so much that it creates a black hole. This would be a black hole the original mass–energy of which was in the form of radiant energy rather than matter;[1] however, there is currently no uniformly accepted method of distinguishing black holes by origin. (See the no-hair theorem.)
John Archibald Wheeler's 1955 Physical Review paper entitled "Geons" refers to the kugelblitz phenomenon and explores the idea of creating such particles (or toy models of particles) from spacetime curvature.[2] This paper coined the term kugelblitz.[3]
A study published in Physical Review Letters in 2024 argues that the formation of a kugelblitz is impossible due to dissipative quantum effects like vacuum polarization, which prevent sufficient energy buildup to create an event horizon.[4] The study concludes that such a phenomenon cannot occur in any realistic scenario within our universe.[3] While the intensity needed to directly verify this calculation is 50 orders of magnitudes higher than the current level of technology allows (as of 2024),[5] the spontaneous disintegration of a high-energy photon into an electron-positron pair (the Schwinger effect) only requires 1000 times more energy than the most advanced lasers can produce.[3]
It has been speculated that the kugelblitz could be the basis interstellar engines (drives) for future black hole starships.[6][5][7]