Black holes are not completely black

New experimental evidence that black holes emit a form of radiation is reported in a paper published online this week in Nature Physics. The study uses an acoustic model of a black hole - from which sound, rather than light, cannot escape - to observe Hawking-like radiation.

In 1974, Stephen Hawking theorized that quantum effects mean black holes cannot be completely black, but must rather emit a type of radiation, now known as Hawking radiation. However, as the amount of radiation emitted is very small, it has not been observed at an actual astrophysical black hole. Acoustic black holes - which are created in atomic Bose-Einstein condensates - offer the possibility of observing an analogue of Hawking radiation in the lab.

Jeff Steinhauer provides the strongest claims to date that an analogue of this coveted Hawking radiation can be seen in such systems. Unlike previous efforts, he provides evidence that particles escaping the black hole are quantum entangled with a partner particle being pulled into the black hole - a crucial signature of Hawking radiation. This is the first time that evidence for such entanglement between Hawking pairs has ever been claimed.

doi: 10.1038/nphys3863

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