Since we've never technically seen a black hole, we've never seen one die; however, conventional thought suggests that, after black holes become ripe, they start gradually leaking radiation from particle pair annihilation — called Hawking radiation (after its discoverer, Stephen Hawking) — out into space. This leakage also results in the black hole's mass reducing, until eventually, they evaporate into nothingness, potentially taking all of the information they once held with them.

Over time, this view has shifted somewhat — from black holes being non-radiating bodies that live forever, to finite sources of power — but now, a new hypothesis essentially overturns conventional wisdom, suggesting that black holes go out with a bang instead of a whimper.

Meet the Polar Opposite of Black Holes:

In addition to the black holes we all know and love, Einstein's theory of general relativity also lends credence to something called "white holes." They, by nature, are the complete opposite of black holes. Instead of typical black hole behavior — drawing matter in, sucking it down, and keeping it in the singularity forever — white holes are repulsive. This means that, instead of drawing matter toward the event horizon and trapping it there, matter could never reach the event horizon no matter how hard it tried.

Now, a team of researchers have published an extremely interesting paper that finally sheds some light on how white holes might form, and believe me when I tell you, it's very interesting. 

The team suggests that white holes are essentially born alongside black holes — a few thousandths of a second after, to be precise — but the very characteristics that define them mask the true nature of the objects. “Importantly, the process is very long seen from the outside, but is very short for a local observer at a small radius,” explained one of the researchers.

To expand, we know that gravity has a discernible impact on the rate at which time flows. Time ticks differently on Earth than from beyond its horizon, and time flows at a different rate for things in low-Earth orbit than from within (or near) a black hole's event horizon. 

We call this effect "time dilation," and it plays a huge role in how we perceive black hole activity. Because of time dilation's effects, when incoming matter approaches a black hole's event horizon, we never really see it fall in. Instead, the image is a lot like a Polaroid, it just freezes in place and slowly disappears from view. Making it more difficult is the fact that black holes spin at an impressive rate. with some clocking in at nearly half the speed of light. If anything somehow managed to match the maximum speed (excluding photons, obviously), time would cease to flow almost entirety.

To the rest of the universe, things unfold the way they normally would; — with stars forming and dying in equal measure, while entropy continues its descent into disorder — but from the black hole's perspective, hardly any time would've passed at all. 

Applying this on a large-scale, from our vantage point, it would seem as if black holes live for huge expanses of time, when, in fact, they simmer down rapidly, before transforming into a white hole. Following the transformation, they would eject huge quantities of high-energy cosmic radiation in the form of gamma-ray bursts.

Delving Deeper: 

According to nature, “If the authors are correct, tiny black holes that formed during the very early history of the Universe would now be ready to pop off like firecrackers and might be detected as high-energy cosmic rays or other radiation. In fact, they say, their work could imply that some of the dramatic flares commonly considered to be supernova explosions could in fact be the dying throes of tiny black holes that formed shortly after the Big Bang.”

The concept, which was discussed in detail in the latest edition of "Nature," is built on the the tenets of quantum gravity. Under this scenario, the effects of quantum gravity (also known as loop quantum gravity, or LQG) —where the fabric of spacetime is composed of tiny, interconnecting loops, instead of being seamless and perfectly smooth — would take the wheel, inevitably prohibiting the collapse from reaching a certain point. This halt would be the result of the loops themselves, which, like subatomic particles, can not be broken down any further.

Mechanically, once newly-formed black holes reach the critical point when they physically cannot collapse any further, internal pressures build up until black holes start exerting themselves outwardly, causing the objects to spew their innards back out into space (effectively marking the transition from a white to a black hole).

"Rather than being shrouded by a true, eternal event horizon, the event would be concealed by a temporary 'apparent horizon," says one of the researchers.

Paradox Reduction:

As speculative as it might be, this new hypothesis would shed some light on one of the largest black hole conundrums,;one that deals with how information is dealt with once it becomes trapped by a black hole. You see, there is this principle that says information can be neither be created or destroyed — which in the context of a black hole, includes key details about the star that collapsed into a singularity, along with the matter that fell into it over time — it, like energy, must be conserved.

Yet the very nature of black holes dictates that nothing can escape from their immensely powerful gravitational clutch, thus the information that is sucked should effectively be destroyed (or, at the very least, this information should never be returned back into the universe), but again, that violates a fundamental principle in physics, so that information must be returned somewhere along the way. Since we can't peer into the belly of a black hole, or see how the laws of physics play out within a singularity, there is a disconnect between black hole mechanics and classical physics.

Now, if black holes eventually transform into white holes, they would essentially push the reset button where matter and information are concerned. So if this hypothesis proves correct, it would be helpful in a number of ways. Steven Giddings, a theoretical physicist from the University of California in Santa Barbara (who wasn't involved in this study) touched base on the implications: “It would be important. Understanding how information escapes from a black hole is the key question for the quantum mechanics of black holes, and possibly for quantum gravity itself.”

Read more about the paper here.

This article barely touches base on white holes. Learn all about them here.