Eternal black holes are the ultimate cosmic safes

If you wanted to hide something away for all eternity, where could you put it? Black holes might seem like a safe bet, but Stephen Hawking famously calculated that they leak radiation, and most physicists now think that this radiation contains information about their contents. Now, there may be a way to make an "eternal" black hole that would act as the ultimate cosmic lockbox.

The recipe for this unlikely object was discovered by looking at an even more abstruse entity, the white hole. White holes are black holes that run backwards in time, throwing out matter instead of sucking it in. Where a black hole might form from a collapsing star, a white hole would explode and leave a star in its place. White holes have never been observed, though general relativity predicts they could exist in principle.

Stephen Hsu of the University of Oregon in Eugene wanted to caculate whether a white hole would emit radiation like a black hole. He considered the special case of a white hole sitting in a perfect vacuum, and calculated that when it spits out its contents, there is a burst of radiation essentially identical to a black hole's Hawking radiation