When black holes become unstable?

There are several ways to create a black hole from collapsing core of a supernova before the neutron stars merge with the collapse of a huge number of substances. If we take the lower limit, black holes can have a 2.5 — 3 solar masses, but at the upper limit of a supermassive black hole can exceed the mass of 10 billion solar. They usually are in the centers of galaxies. How they are stable? What is a black hole runs out first: large and voracious or small?

Is there a critical size for the stability of a black hole? A black hole weighing 10to 12 pounds can be stable for several billion years. But a black hole in the mass range 105 can explode in a second and not exactly be stable. Where is the Golden mean in which the inflow of matter is Hawking radiation?

Stability of black holes

The first thing you need to start, is a stable black hole. Any other object in the Universe, astrophysical or otherwise, there are forces holding it together against the Universe, which is trying to break. The hydrogen atom is a strong structure; a single ultraviolet photon can destroy it, iniziava electron. For the destruction of the atomic nucleus need a more high-energy particle like a cosmic ray, an accelerated proton or gamma-ray photon.

But large structures like planets, stars or even galaxies, the gravitational forces that hold them is huge. As a rule, to break such a mega structure is necessary for a thermonuclear reaction, or incredibly strong, the effect of gravity from the outside — for example from a passing star, black hole or galaxy.

In the case of black holes, however, it is not so. Black hole mass will instead be distributed in volume, is compressed into a singularity. From a non-rotating black hole is one point with zero dimension. From a rotating black hole is not much better: infinitely thin, one-dimensional ring.

Furthermore, the content of the mass-energy in the black hole within the event horizon. Black holes are the only objects in the Universe, which is the event horizon: the boundary, overcoming which it is impossible to go back. No acceleration and therefore no force can pull matter, mass or energy from the event horizon beyond.

This could mean that black holes, formed in any way possible, can only increase and never be destroyed. And they grow steadily and continuously. We observe various phenomena in the Universe such as:

  • quasars;
  • blazey;
  • the active nuclei of galaxies;
  • microquasars;
  • the star is not emitting any light;
  • x-ray and the radio bursts from the galactic centers;

which leads us to black holes. Determining their masses, we are trying to learn and the physical size of their event horizon. All that faces him, cross him, or even hurt, will inevitably fall inside. And then, thanks to conservation of energy, will increase and the mass of the black hole.

This process occurs with each black hole known to us. Material from other stars, cosmic dust, interstellar matter, molecular clouds, even radiation and neutrinos left over from the Big Bang — everything goes there. Any matter colliding with a black hole increases its mass. The growth of black holes depends on the density of matter and energy surrounding the black hole; the monster at the center of our milky Way is growing at the speed of 1 solar mass in 3000 years; the black hole at the center of the Sombrero galaxy is growing at the speed of 1 solar mass in 20 years.

The larger and heavier your black hole, on average, the faster it grows, depending on the encountered material. Over time, the rate of growth is slowing, but since the Universe is only about 13.8 billion years, black holes grow well.

On the other hand, black holes don’t just grow with time; there is also a process of evaporation: Hawking radiation. This is due to the fact that the space is strongly curved near the event horizon, but straightens when removed. If you stay at a distance, you can see a slight radiation emitted from the curved region near the event horizon related to the fact that the quantum vacuum has different properties in different curved regions of space.

The end result is that black holes emit thermal radiation of a black body (mostly in the form of photons) in all directions around itself, in a volume of space, which basically concludes about ten Schwarzschild radii at the location of the black hole. And it may seem strange, but the smaller the black hole the faster it evaporates.

Hawking radiation is an incredibly slow process by which a black hole with the mass of our Sun will be gone in 10to 64 years; the hole in the center of our milky Way — 10of 87 years, and the most massive in the Universe through the 10100 years. To calculate the evaporation time of a black hole with a simple formula, you need to take the time frame of our Sun and multiply by (black hole mass/solar mass)3.

From which it follows that a black hole with the mass of the Earth will live 10of 47 years; a black hole with the mass of the great pyramid at Giza (6 million tons) is about a thousand years; with the mass of the Empire state building is about a month; with man PS. The less weight, the faster evaporates the black hole.

As far as we know, the universe could contain black holes are unimaginably different sizes. If she were filled with light by black holes — a billion tons — they would have evaporated, to date there is No evidence that there are black holes with a mass between the lungs and those that are born in the process of merging neutron stars — in theory, they have a mass of 2.5 solar. Above these limits of x-ray studies indicate the existence of black holes in the range of 10-20 solar masses; LIGO showed a black hole of 8 to 62 solar masses; also find supermassive black holes throughout the Universe.

Today, all existing black holes gather matter faster, than they lose as a result of Hawking radiation. A black hole of solar mass loses about 10-28 j of energy every second. But when you consider that:

  • even a single photon of the background radiation is a million times more energy;
  • Such 411 photons per cubic centimeter of space left over after the Big Bang;
  • they move at the speed of light, colliding 10 trillion times per second in each cubic centimeter;

even an isolated black hole in the depths of intergalactic space will have to wait until the universe is not going to grow up to 10to 20 years — a billion times more than her current age before the growth rate of the black hole will fall below the rate of Hawking radiation.

But let’s play a game. Suppose you live in the intergalactic space, away from normal matter and dark matter, away from all cosmic rays, stellar radiation, and neutrinos, and you are left with only photons from the Big Bang with which to chat. How big should be your black hole to the rate of evaporation (Hawking radiation) and the absorption of photons by the black hole your (growth) balance each other?

The answer is around 1023 kg, ie approximately the mass of the planet mercury. If mercury were a black hole, it would be half a millimeter in diameter and would radiate about 100 trillion times faster than a black hole of solar mass. It was with this mass in our Universe a black hole has swallowed as much microwave radiation as lost in the process of Hawking radiation.

But if you want a realistic black hole you can’t isolate her from the rest of matter in the Universe. Black holes, even after being thrown out of the galaxies are still flying through the intergalactic medium in the face of cosmic rays by the stars, neutrinos, dark matter and all particles, massive and massless. The cosmic microwave background cannot be avoided wherever you go. Black holes continuously absorb matter and energy and grow in mass and size. Yes, they also radiate energy, but that all exist in our Universe black holes began to dwindle faster than they grow, should be about 100 quintillion years.

And on final evaporation will take even more.

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