Black holes die by slowly radiating away their mass over incomprehensibly long timescales, eventually ending in a violent burst of energy. The process is called Hawking radiation, and for a typical stellar-mass black hole, complete evaporation would take roughly 10^67 years. For the largest supermassive black holes, that number stretches to around 10^100 years, a one followed by a hundred zeros, far longer than the current age of the universe.
How Black Holes Lose Mass
In 1974, Stephen Hawking showed that black holes are not truly black. Quantum effects near the event horizon cause pairs of particles to spontaneously pop into existence. Normally these particle pairs annihilate each other almost instantly, but at the very edge of a black hole, one particle can fall in while the other escapes into space. That escaping particle carries energy away, and because energy and mass are equivalent, the black hole loses a tiny amount of mass each time this happens.
This radiation has a temperature, and it follows a perfect blackbody spectrum, meaning the black hole glows like a heated object. Here’s the counterintuitive part: smaller black holes are hotter. A black hole with the mass of our Sun would have a temperature just a tiny fraction of a degree above absolute zero, making its radiation negligible. But as a black hole shrinks, its temperature rises, which makes it radiate faster, which makes it shrink more. The process accelerates over time.
For most of a black hole’s life, this radiation is fantastically slow. A stellar-mass black hole emits so little energy that it actually gains more mass from absorbing cosmic microwave background radiation than it loses to Hawking radiation. Only after the universe cools enough, billions of years from now, will most black holes begin losing mass faster than they gain it. At that point, the long countdown to death truly begins.
The Final Explosion
As a black hole shrinks, its temperature climbs and its radiation output increases. This feedback loop stays gentle for most of the evaporation process, but in the final stages, things get extreme. Once the black hole is smaller than an atom, the temperature reaches trillions of degrees and the radiation becomes a torrent of high-energy particles.
In its last fraction of a second, the black hole releases a spectacular burst of gamma rays, neutrinos, and other particles. Theoretical models suggest this final explosion can last anywhere from a tenth of a second to about 15 minutes, with most of the energy concentrated in the MeV range (comparable to the energy of particles produced in nuclear reactions). The charged particles streaming outward form a dense plasma that expands outward at relativistic speeds.
A 2025 MIT study proposed that this kind of explosion may have already been detected indirectly. Scientists at the KM3NeT neutrino telescope recorded a neutrino with an energy exceeding 100 peta-electron-volts, the highest-energy neutrino ever observed. The MIT team calculated that a primordial black hole in its final nanosecond would emit roughly a sextillion neutrinos at exactly that energy level. They estimated an 8 percent chance that such an explosion could occur close enough to our solar system, once every 14 years, for one of those neutrinos to reach Earth. If confirmed, it would be the first observational evidence of Hawking radiation from any black hole.
What’s Left Behind
This is where physics gets genuinely uncertain. The standard prediction from Hawking’s original work is that a black hole radiates away completely, leaving nothing behind but a spray of particles. But this creates serious theoretical problems, and physicists have proposed several alternatives.
One possibility is that evaporation stops just before the black hole disappears entirely, leaving behind a remnant about the size of the Planck length (roughly 10^-35 meters, far smaller than any subatomic particle). The generalized uncertainty principle, a modification of quantum mechanics that accounts for gravity, suggests there may be a minimum size below which a black hole simply cannot shrink. These remnants would have roughly the Planck mass, about 22 micrograms, and would interact with the rest of the universe only through gravity. Some physicists have proposed that trillions of these remnants, produced by primordial black holes in the early universe, could account for dark matter.
Another possibility comes from quantum gravity research. Recent work using the Wheeler-DeWitt equation, one of the leading frameworks for combining quantum mechanics and general relativity, found that the crushing singularity at a black hole’s center may not actually exist. The quantum wave function near where the singularity should be remains finite and well-behaved, suggesting that quantum effects smooth out the infinite density predicted by classical physics. If the singularity was never truly there, the endpoint of evaporation could look very different from what we currently assume.
The Information Paradox
Perhaps the deepest puzzle about black hole death is what happens to information. In physics, information about a system’s quantum state is never supposed to be destroyed. You can scramble it beyond recognition, but it should always be recoverable in principle. Black hole evaporation threatens to violate this rule.
When matter falls into a black hole, all its detailed quantum information appears to be trapped inside. Hawking radiation, as originally described, comes out in a random thermal spectrum that contains none of that original information. So if the black hole evaporates completely, the information seems to vanish from the universe, which would break one of the deepest principles in physics.
Several proposed solutions exist, none fully proven. One approach, called complementarity, argues that the information exists in two forms simultaneously: encoded on the black hole’s boundary for outside observers, and carried through to the interior for someone falling in. No single observer can access both copies, so no physical law is violated. But in 2012, researchers found scenarios where an observer could access both copies, which would violate quantum mechanics in a different way. Their proposed fix was a “firewall,” a wall of extreme energy at the event horizon that would destroy anything on contact, preventing anyone from comparing the two copies.
More recent work has explored the idea of “islands,” regions that are technically inside the black hole but whose quantum information is somehow accessible from outside. This approach appears to show that information does gradually leak out through Hawking radiation over the black hole’s lifetime, resolving the paradox mathematically, though the physical mechanism remains debated.
The Timeline of Black Hole Death
No black hole formed from a collapsing star has died yet. The universe is only about 13.8 billion years old, and even the smallest stellar black holes need something like 10^67 years to evaporate. The supermassive black holes at the centers of galaxies will persist for 10^100 years, outlasting every star, every planet, and every other structure in the cosmos.
The only black holes that could be dying right now are primordial ones, hypothetical black holes formed in the extreme conditions of the Big Bang. Any primordial black hole lighter than about 10^15 grams (roughly the mass of a small asteroid) would have had enough time to evaporate by now. Heavier ones would still be out there, slowly shrinking. Their evaporated particles are already constrained by observations: they would have affected the formation of elements in the early universe, left imprints on the cosmic microwave background, and contributed to the gamma-ray and cosmic-ray backgrounds we measure today.
In the far future, after the last stars have burned out and the universe has expanded into a cold, dark void, black holes will be the last complex objects remaining. Their eventual evaporation will mark the final act of the stelliferous era, a slow fade into a universe of nothing but diffuse radiation and elementary particles.