In loop quantum gravity theory, a Planck star is a hypothetical astronomical object, theorized as a compact, exotic star, that exists within a black hole 's event horizon, created when the energy density of a collapsing star reaches the Planck energy density.

In a Planck star, the matter is compressed to the smallest possible scale - the Planck length. If a black hole harbored a Planck star in its core, the matter would not be compressed infinitely but would have an infinitesimally tiny amount of volume - therefore eliminating the tricky singularity.

Collapsing matter does not disappear at the center: it bounces up through the white hole. Energy and information that fell into the black hole emerge from the white hole. The configuration where the compression is maximal, which separates the black hole from the white hole, is called a “Planck star.”