A lot of laws of physics seem to be ignored or omitted when it comes to black holes, so there always seems to be a missing link when it comes to understanding how they work.
BLACK HOLE Vs WHITE HOLE. One theory to mitigate these unknowns is the presence of white holes – a hypothetical equal and opposite version of a black hole that was first discussed in the early 1960s by the Russian cosmologist Igor Novikov.
ORIGIN OF THE CONCEPT OF WHITE HOLE. The origin of where a white hole would come from is currently unknown.
One theory is that a white hole is created from extremely old black holes that have started to expel all of the information they have attained, thus meaning that the matter was never entirely eradicated.
Another more thought provoking hypothesis is that they are portals of black holes from entirely different dimensions. If a supernova occurred in a different dimension, the resulting black hole could have created a white hole in a different dimension.
Of course, the whole idea of white holes existing is entirely hypothetical so far as there has been no evidence of any existing apart from one gamma ray burst in 2006 that exhibited strange properties that were not expected.