Scientists at Lawrence Livermore National Laboratory in California suspect that midsize black holes might be just the right size to provide enough gravitational force to reignite a dead white dwarf star — the stellar corpse of a star that's about the mass of the sun and that's used up its nuclear fuel. To test their idea, the team members ran supercomputer simulations of dozens of different close-encounter scenarios between these dead stars and midsize black holes. Every time a white dwarf got close to the Goldilocks black hole, the star reignited. The gravitational force from the black hole would cause the...