The conventional wisdom is that stars that are many times larger than our own sun have nuclear reactions that eventually use up all of their hydrogen, which they convert to helium. When the helium or other fuel is gone, the star will collapse because it will still have incredible amounts of gravity. The gravity cannot stop the collapsing. The star is dark because matter and even light is trapped and cannot escape. The enormous gravity is still there however, leading to the name “black hole”, according to a very basic understanding from Scholastic.
Humans think that they have found black holes when observing that gases and other things appear to be “sucked” into something that actually cannot be seen.
A “white hole” is supposed to be the opposite of a black hole, where matter and light appear to be spewing from a very small point.
Human understanding likes to deal with opposites. If one entity exists that can suck up everything, then an entity that spews out everything must also exist.
A “white hole” has not exactly been discovered. Only one event with the potential for being a white hole has been observed. There was evidence from 2006 that a fierce gamma ray burst went on for 102 seconds. Before then, gamma ray bursts of that length and strength were observed only when a supernova was associated with the burst. But in the 2006 observation, no associated supernova could be found.
The power and the ferocity of the burst, with no supernova to explain it, led to the idea of an opposite to a black hole, or a white hole. Thus, the gamma ray burst may have been the first observation of a white hole. According to iO9, one speculation is that an object appeared and spewed out some matter. Then the object is believed to have produced the explosive and unusually strong burst while or before collapsing in on itself. Finally, the object disappeared from any observations.
That strange burst has been called a “hybrid burst”, and the object or “white hole” is gone, so astronomers will now look to see if another one of these burst has occurred. If another one is found, then more data and analysis can go on. But right now, the closest thing to evidence of a theoretical white hole involves a very strong and strange gamma ray burst, no observable source object, and no associated supernova.
After that, everything goes mathematical and theoretical. The events that look like white holes may turn out to be so rare that they may simply not be observable.
But if black holes are the stuff of science fiction books, television shows and films, then an idea generating new universe is coming. That idea generating new universe could potentially include white holes, leading to even more creative fiction and thought.
Meanwhile, the human intellect would be more comfortable with nature if there could be confirmation that there are white holes to serve as a balance and an opposite to black holes.
