Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

A double analytic continuation of this type of solution reveals the "bubble of nothing" instability of the Kaluza-Klein vacuum, as discovered by Edward Witten. Recently, a correspondence between a chiral half of a two-dimensional conformal field theory and those of extremal Kerr type has been suggested. Above a minimum temperature, anti de Sitter space has a phase transition to a space containing one of these, as shown by Page and Hawking. They have entropy proportional to their area, and a temperature proportional to their surface gravity. Supermassive ones lie at the center of most or all galaxies. For 10 points, what are these objects in general relativity, discovered originally by Karl Schwarzschild, from which light does not escape
Science