White hole

In general relativity, a white hole is a hypothetical region of spacetime and singularity that cannot be entered from the outside, although energy-matter, light and information can escape from it. In this sense, it is the reverse of a black hole, which can be entered only from the outside and from which energy-matter, light and information cannot escape. White holes appear in the theory of eternal black holes. In addition to a black hole region in the future, such a solution of the Einstein field equations has a white hole region in its past.[1] This region does not exist for black holes that have formed through gravitational collapse, however, nor are there any observed physical processes through which a white hole could be formed.

General relativity
${\displaystyle G_{\mu \nu }+\Lambda g_{\mu \nu }={\kappa }T_{\mu \nu }}$
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Supermassive black holes (SMBHs) are theoretically predicted to be at the center of every galaxy and that possibly, a galaxy cannot form without one. Stephen Hawking[2] and others have proposed that these supermassive black holes spawn a supermassive white hole.[3]