Ask Ethan: when black holes become unstable?

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The simulated decay of a black hole is not only reflected in the emission of radiation, but in the decay of the central orbiting mass that keeps most of the stable objects. Black holes are not static objects, but rather change over time.Communicating the science of the EU

There are several ways to create the black holes that we know in the Universe, from the supernovae of the collapse of the nucleus to the fusion of neutron stars to the direct collapse of enormous quantities of matter. In the smallest part, we know of black holes that can only be 2.5 to 3 times the mass of our Sun, while at the larger end, the supermassive ones that exceed 10 billion solar masses reside in the centers of galaxies . But it is so? And how stable are the black holes of different masses? This is what Nyccolas Emanuel wants to know, & nbsp; as he asks:

Is there a critical dimension for the stability of the black hole? [A] 1012 kg [black hole] it's already stable for a couple of billions of years. However, a [black hole] in the interval of 105 kg, could explode in a second, therefore, definitely not stable … I guess there is a critical mass for a [black hole] where will the flow of acquired matter be equal to the Hawking evaporation?

There's a lot to do here, so let's open everything.

Black holes will devour whatever they encounter. Although this is a great way to grow black holes, Hawking radiation also ensures that black holes will lose mass. Derive when one defeats the other is not a trivial task.Radiography: NASA / CXC / UNH / D.Lin et al, Optician: CFHT, Illustration: NASA / CXC / M.Weiss

The first thing to start with is the stability of a black hole itself. For any other object in the Universe, astrophysical or otherwise, there are forces that hold it together against anything the Universe could do to try and tear it apart. A hydrogen atom is a structure held tightly together; a single ultraviolet photon can destroy it by ionizing its electron. An atomic nucleus needs a much higher energy particle to make it explode, like a cosmic ray, an accelerated proton, or a gamma ray photon.

But for larger structures, like planets, stars or even galaxies, the gravitational forces that hold them together are enormous. Normally, it takes an uncontrolled fusion reaction & nbsp; or an incredibly strong external gravitational force, like a passing star, a black hole or a galaxy, to snatch a separate megastructure.

NGC 3561A and NGC 3561B collided and produced huge stellar tails, plumes and perhaps even "ejecta" that are condensing to make tiny "new" galaxies. The young hot stars shine blue where the rejuvenated star formation is occurring. Forces, like those between galaxies, can tear stars, planets or even entire galaxies. The black holes, however, will remain.Adam Block / Mount Lemmon SkyCenter / University of Arizona

For black holes, however, something is fundamentally different. Rather than their mass being distributed on a volume, it is compressed into a singularity. For a non-rotating black hole, this is just a single zero-dimensional point. (For those rotating, it's not much better: an infinitely thin and one-dimensional ring.)

Furthermore, all the contents containing mass and energy of a black hole are contained within an event horizon. Black holes are the only objects in the universe that contain a horizon of events: a boundary where, if you slip into it, it is impossible to escape. No acceleration, and therefore no force, no matter how strong, will ever be able to extract matter, mass or energy from within the horizon of events outside the Universe.

Impression of the artist of the active galactic nucleus. The supermassive black hole at the center of the accretion disk sends a narrow stream of high-energy matter into space, perpendicular to the disk. A blazar about 4 billion light years away is the origin of many of the highest energy cosmic rays and neutrinos. Only matter from the outside of the black hole can leave the black hole; it matters from within the horizon of events can never run away.DESY, Science Communication Lab

This could imply that black holes, once formed by any means possible, can only grow and never be destroyed. In fact, they grow up and inexorably to that. We observe all types of phenomena in the universe, such as:

  • quasars,
  • blazar,
  • active galactic nuclei,
  • microquasars,
  • stars that orbit large masses that do not emit light of any kind,
  • and flaring, X-rays and radio emissions from galactic centers,

which are all meant to be guided by black holes. If we deduce their masses, we can then know the physical dimensions of their horizons of events. Anything that collides with it, crosses it, or even grazes it, will inevitably fall into it. And then, with the conservation of energy, it must inevitably increase the mass of the black hole.

An illustration of an active black hole, one that encloses matter and accelerates a part of it towards the outside in two perpendicular jets, is an excellent descriptor of how quasars work. The matter that falls into a black hole, of any variety, will be responsible for the additional growth both in terms of mass and size for the black hole.Mark A. Garlick

This is a process that, on average, is happening for every black hole in the Universe known today. Material from other stars, cosmic dust, interstellar matter, gas clouds or even radiation and neutrinos left behind by the Big Bang can contribute. The interference of dark matter will collide with the black hole, also increasing its mass. All said, black holes grow depending on the density of matter and energy that surrounds them; the monster at the center of our Milky Way grows at the rate of about one solar mass every 3000 years; the black hole in the center of the Sombrero galaxy it grows at the rate of a solar mass every two decades.

The bigger and heavier your black hole is, the faster it grows on average, it depends on the other material it encounters. Over time, the growth rate will decrease, but with a Universe that only has about 13.8 billion years, they continue to grow in a prodigious way.

If the horizons of the event are real, a star that falls into a central black hole would simply be devoured, leaving no trace of the encounter. This process, of black holes that grow because the matter clashes with their horizons of events, can not be prevented.Mark A. Garlick / CfA

On the other hand, black holes are not simply growing over time; there is also a process through which they evaporate: Hawking radiation. This was the theme of last week Ask Ethanand it is due to the fact that space is strongly curved near the event horizon of a black hole, but flatter than far. If you are a very distant observer, you will see a not inconsiderable amount of radiation emitted from the curved region near the event horizon, due to the fact that quantum vacuum has different properties in differently curved regions of space.

The net result is that black holes are activated by emitting thermal radiation, of black body (mainly in the form of photons) in all directions around it, on a volume of space that encapsulates approximately ten Schwarzschild rays of the black hole position. And, perhaps counterintuitively, the less massive your black hole, the faster it evaporates.

The event horizon of a black hole is a spherical or spherical region from which nothing, not even light, can escape. But outside the event horizon, the black hole is expected to emit radiation. Hawking's 1974 work was the first to prove it and it was probably his greatest scientific achievement.NASA; J & ouml; Wilms (T & uuml; bingen) et al.; ESA

Hawking radiation is an incredibly slow process, in which a black hole the mass of our Sun would employ 1064& nbsp; years to evaporate; that at the center of the Milky Way would require 1087& nbsp; years and the most massive of the Universe could take up to 10100& Nbsp; years. In general, a simple formula that you can use to calculate the evaporation time for a black hole is to take the chronological scale for our Sun and multiply it by:

(Mass of the black hole / Mass of the sun)3,

which means that a black hole in the land mass would survive 1047& Nbsp; years; a mass of the Great Pyramid of Giza (~ 6 million tons) would remain for about a millennium; one of the masses of the Empire State Building would last about a month; a mass of an average human would have lasted just under a picosecond. As the mass decreases, it evaporates more quickly.

The decay of a black hole, through Hawking radiation, should produce the observable signatures of photons for most of its life. Precisely at the final stages, however, the evaporation rate and the Hawking radiation energies indicate that there are explicit predictions for particles and antiparticles that would be unique. A human mass black hole would evaporate into a mere picosecond.ortega-images / pixabay

As far as we know, the Universe could contain black holes of an extraordinarily large range of masses. If you were born with a light one – nothing under about a billion tons & nbsp; – all those would have evaporated every day. There is no evidence of heavier black holes than this until you get to those created by star-neutron neutron star mergers, which in theory start to rise to about 2.5 solar masses. Beyond that, X-ray studies indicate the existence of black holes in the range of ~ 10-20 solar masses; LIGO showed us black holes ranging from 8 to about 62 solar masses; and astronomy studies reveal the supermassive black holes that are found throughout the universe.

There is a wide range of black holes that we know, but also a wide range of studies that rule out the black holes that make up the bulk of dark matter on a wide variety of regimes.

Constraints on dark matter from primordial black holes. There is an overwhelming series of evidence that indicates that there is a large population of black holes created in the primordial universe that encompasses our dark matter.Fig. 1 by Fabio Capela, Maxim Pshirkov and Peter Tinyakov (2013), through http://arxiv.org/pdf/1301.4984v3.pdf

Today all the black holes that actually exist physically are gaining material at a much greater rate than the Hawking radiation is causing them to lose mass. For a black hole of solar mass, it loses about 10-28 Joule of energy every second. Considering that:

  • even a single photon of the cosmic microwave background has about a million times that energy,
  • there are about 411 such photons (left from the Big Bang) per cubic centimeter of space,
  • and they move at the speed of light, or about 10 & nbsp; trillion photons per second collide with every square centimeter of area occupied by an object,

even an isolated black hole in the depths of intergalactic space would have to wait for the Universe to be around 10 o'clock20 years – more than a billion times its current age – before the growth rate of the black hole falls below the Hawking radiation rate.

The nucleus of the galaxy NGC 4261, like the nucleus of many galaxies, shows the signs of a supermassive black hole in infrared and X-ray observations. As the matter falls inside, the black hole continues to grow.NASA / Hubble and ESA

But let's play. Assuming that you lived in intergalactic space, away from all normal matter and dark matter, away from all cosmic rays and stellar radiation and neutrinos, and that only the photons left behind by the Big Bang to fight with. How big should your black hole be so that the rate of Hawking radiation (evaporation) and the rate of absorption of the photon from your black hole (growth) will balance one another?

The answer comes to around 1023 kg, or approximately the mass of the planet Mercury. If it were a black hole, Mercury would have a diameter of about half a millimeter and would radiate about 100 trillion times faster than a solar-mass black hole. This is the mass, in today's universe, that it would take a black hole to absorb all the microwave background cosmic radiation it would emit in Hawking radiation.

As a black hole shrinks in mass and radius, the Hawking radiation emanating from it becomes ever larger in terms of temperature and power. However, over time the Hawking radiation speed exceeds the growth rate, there will be no more stars burning in our cosmos.NASA

For a realistic black hole, you can not isolate it from the remaining matter in the Universe. Black holes, even if they are expelled from galaxies, continue to fly through the intergalactic medium, encountering cosmic rays, starlight, neutrinos, dark matter and all sorts of other particles, both massive and massless. The background of cosmic microwaves is inevitable, no matter where you go. If you are a black hole, you constantly absorb matter and energy and, consequently, increases both in terms of mass and size. Yes, you too radiate energy in the form of Hawking radiation, but for all the black holes that really exist in our Universe, it will take at least 100 quintillion years because the rate of growth falls below the radiation rate and very, very longer for them to finally evaporate.

The black holes will eventually become unstable and disappear into nothing but radiation, but unless we create a very low mass, somehow, nothing else in the Universe will be around to witness them when they go.


Send your questions to Ethan a startswithabang at gmail dot com!

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The simulated decay of a black hole is not only reflected in the emission of radiation, but in the decay of the central orbiting mass that keeps most of the stable objects. Black holes are not static objects, but rather change over time.Communicating the science of the EU

There are several ways to create the black holes that we know in the Universe, from the supernovae of the collapse of the nucleus to the fusion of neutron stars to the direct collapse of enormous quantities of matter. In the smallest part, we know of black holes that can only be 2.5 to 3 times the mass of our Sun, while at the larger end, the supermassive ones that exceed 10 billion solar masses reside in the centers of galaxies . But it is so? And how stable are the black holes of different masses? This is what Nyccolas Emanuel wants to know, as he asks:

Is there a critical dimension for the stability of the black hole? [A] 1012 kg [black hole] it's already stable for a couple of billions of years. However, a [black hole] in the interval of 105 kg, could explode in a second, therefore, definitely not stable … I guess there is a critical mass for a [black hole] where will the flow of acquired matter be equal to the Hawking evaporation?

There's a lot to do here, so let's open everything.

Black holes will devour whatever they encounter. Although this is a great way to grow black holes, Hawking radiation also ensures that black holes will lose mass. Derive when one defeats the other is not a trivial task.Radiography: NASA / CXC / UNH / D.Lin et al, Optician: CFHT, Illustration: NASA / CXC / M.Weiss

The first thing to start with is the stability of a black hole itself. For any other object in the Universe, astrophysical or otherwise, there are forces that hold it together against anything the Universe could do to try and tear it apart. A hydrogen atom is a structure held tightly together; a single ultraviolet photon can destroy it by ionizing its electron. An atomic nucleus needs a much higher energy particle to make it explode, like a cosmic ray, an accelerated proton, or a gamma ray photon.

But for larger structures, like planets, stars or even galaxies, the gravitational forces that hold them together are enormous. Normally, it requires an out-of-control fusion reaction or an incredibly strong external gravitational force – like a passing star, a black hole or a galaxy – to tear apart such a megastructure.

NGC 3561A and NGC 3561B collided and produced huge stellar tails, plumes and perhaps even "ejecta" that are condensing to form small "new" galaxies. The young hot stars shine blue where the rejuvenated star formation is occurring. Forces, like those between galaxies, can tear stars, planets or even entire galaxies. The black holes, however, will remain.Adam Block / Mount Lemmon SkyCenter / University of Arizona

For black holes, however, something is fundamentally different. Rather than their mass being distributed on a volume, it is compressed into a singularity. For a non-rotating black hole, this is just a single zero-dimensional point. (For those rotating, it's not much better: an infinitely thin and one-dimensional ring.)

Furthermore, all the contents containing mass and energy of a black hole are contained within an event horizon. Black holes are the only objects in the universe that contain a horizon of events: a boundary where, if you slip into it, it is impossible to escape. No acceleration, and therefore no force, no matter how strong, will ever be able to extract matter, mass or energy from within the horizon of events outside the Universe.

Impression of the artist of the active galactic nucleus. The supermassive black hole at the center of the accretion disk sends a narrow stream of high-energy matter into space, perpendicular to the disk. A blazar about 4 billion light years away is the origin of many of the highest energy cosmic rays and neutrinos. Only matter from the outside of the black hole can leave the black hole; it matters from within the horizon of events can never run away.DESY, Science Communication Lab

This could imply that black holes, once formed by any means possible, can only grow and never be destroyed. In fact, they grow up and inexorably to that. We observe all types of phenomena in the universe, such as:

  • quasars,
  • blazar,
  • active galactic nuclei,
  • microquasars,
  • stars that orbit large masses that do not emit light of any kind,
  • and flaring, X-rays and radio emissions from galactic centers,

which are all meant to be guided by black holes. If we deduce their masses, we can then know the physical dimensions of their horizons of events. Anything that collides with it, crosses it, or even grazes it, will inevitably fall into it. And then, with the conservation of energy, it must inevitably increase the mass of the black hole.

An illustration of an active black hole, one that encloses matter and accelerates a part of it towards the outside in two perpendicular jets, is an excellent descriptor of how quasars work. The matter that falls into a black hole, of any variety, will be responsible for the additional growth both in terms of mass and size for the black hole.Mark A. Garlick

This is a process that, on average, is happening for every black hole in the Universe known today. Material from other stars, cosmic dust, interstellar matter, gas clouds or even radiation and neutrinos left behind by the Big Bang can contribute. The interference of dark matter will collide with the black hole, also increasing its mass. All in all, black holes grow according to the density of matter and energy that surrounds them; the monster at the center of our Milky Way grows at the rate of about one solar mass every 3000 years; the black hole in the center of the Sombrero galaxy grows at the rate of a solar mass every two decades.

The bigger and heavier your black hole is, the faster it grows on average, it depends on the other material it encounters. Over time, the growth rate will decrease, but with a Universe that only has about 13.8 billion years, they continue to grow in a prodigious way.

If the horizons of the event are real, a star that falls into a central black hole would simply be devoured, leaving no trace of the encounter. This process, of black holes that grow because the matter clashes with their horizons of events, can not be prevented.Mark A. Garlick / CfA

On the other hand, black holes are not simply growing over time; there is also a process through which they evaporate: Hawking radiation. This was the subject of last week's Ask Ethan, and it is due to the fact that space is strongly curved near the event horizon of a black hole, but flatter than far. If you are a very distant observer, you will see a not inconsiderable amount of radiation emitted from the curved region near the event horizon, due to the fact that quantum vacuum has different properties in differently curved regions of space.

The net result is that black holes are activated by emitting thermal radiation, of black body (mainly in the form of photons) in all directions around it, on a volume of space that encapsulates approximately ten Schwarzschild rays of the black hole position. And, perhaps counterintuitively, the less massive your black hole, the faster it evaporates.

The event horizon of a black hole is a spherical or spherical region from which nothing, not even light, can escape. But outside the event horizon, the black hole is expected to emit radiation. Hawking's 1974 work was the first to prove it and it was probably his greatest scientific achievement.NASA; Jörn Wilms (Tübingen) et al.; ESA

Hawking radiation is an incredibly slow process, in which a black hole the mass of our Sun would employ 1064 years to evaporate; that at the center of the Milky Way would require 1087 years and the most massive of the Universe could take up to 10100 years. In general, a simple formula that you can use to calculate the evaporation time for a black hole is to take the chronological scale for our Sun and multiply it by:

(Mass of the black hole / Mass of the sun)3,

which means that a black hole in the land mass would survive 1047 years; a mass of the Great Pyramid of Giza (~ 6 million tons) would remain for about a thousand years; one of the masses of the Empire State Building would last about a month; a mass of an average human would have lasted just under a picosecond. As the mass decreases, it evaporates more quickly.

The decay of a black hole, through Hawking radiation, should produce the observable signatures of photons for most of its life. Precisely at the final stages, however, the evaporation rate and the Hawking radiation energies indicate that there are explicit predictions for particles and antiparticles that would be unique. A human mass black hole would evaporate into a mere picosecond.ortega-images / pixabay

As far as we know, the Universe could contain black holes of an extraordinarily large range of masses. If it were born with light ones – something under one billion tons – they would all have evaporated to this day. There is no evidence of heavier black holes than this until you get to those created by star-neutron neutron star mergers, which in theory start to rise to about 2.5 solar masses. Beyond that, X-ray studies indicate the existence of black holes in the range of ~ 10-20 solar masses; LIGO showed us black holes ranging from 8 to about 62 solar masses; and astronomy studies reveal the supermassive black holes that are found throughout the universe.

There is a wide range of black holes that we know, but also a wide range of studies that rule out the black holes that make up the bulk of dark matter on a wide variety of regimes.

Constraints on dark matter from primordial black holes. There is an overwhelming series of evidence that indicates that there is a large population of black holes created in the primordial universe that encompasses our dark matter.Fig. 1 by Fabio Capela, Maxim Pshirkov and Peter Tinyakov (2013), through http://arxiv.org/pdf/1301.4984v3.pdf

Today all the black holes that actually exist physically are gaining material at a much greater rate than the Hawking radiation is causing them to lose mass. For a black hole of solar mass, it loses about 10-28 Joule of energy every second. Considering that:

  • even a single photon of the cosmic microwave background has about a million times that energy,
  • there are about 411 such photons (left from the Big Bang) per cubic centimeter of space,
  • and they move at the speed of light, which means that about 10 trillion photons per second collide with every square centimeter of area occupied by an object,

even an isolated black hole in the depths of intergalactic space would have to wait for the Universe to be around 10 o'clock20 years – more than a billion times its current age – before the growth rate of the black hole falls below the Hawking radiation rate.

The nucleus of the galaxy NGC 4261, like the nucleus of many galaxies, shows the signs of a supermassive black hole in infrared and X-ray observations. As the matter falls inside, the black hole continues to grow.NASA / Hubble and ESA

But let's play. Assuming that you lived in intergalactic space, away from all normal matter and dark matter, away from all cosmic rays and stellar radiation and neutrinos, and that only the photons left behind by the Big Bang to fight with. How big should your black hole be so that the rate of Hawking radiation (evaporation) and the rate of absorption of the photon from your black hole (growth) will balance one another?

The answer comes to around 1023 kg, or approximately the mass of the planet Mercury. If it were a black hole, Mercury would have a diameter of about half a millimeter and would radiate about 100 trillion times faster than a solar-mass black hole. This is the mass, in today's universe, that it would take a black hole to absorb all the microwave background cosmic radiation it would emit in Hawking radiation.

As a black hole shrinks in mass and radius, the Hawking radiation emanating from it becomes ever larger in terms of temperature and power. However, over time the Hawking radiation speed exceeds the growth rate, there will be no more stars burning in our cosmos.NASA

For a realistic black hole, you can not isolate it from the remaining matter in the Universe. Black holes, even if they are expelled from galaxies, continue to fly through the intergalactic medium, encountering cosmic rays, starlight, neutrinos, dark matter and all sorts of other particles, both massive and massless. The background of cosmic microwaves is inevitable, no matter where you go. If you are a black hole, you constantly absorb matter and energy and, consequently, increases both in terms of mass and size. Yes, you too radiate energy in the form of Hawking radiation, but for all the black holes that really exist in our Universe, it will take at least 100 quintillion years because the rate of growth falls below the radiation rate and very, very longer for them to finally evaporate.

The black holes will eventually become unstable and disappear into nothing but radiation, but unless we create a very low mass, in some way, nothing else in the universe will be around to witness them when they go.


Send your questions to Ethan at startswithabang at gmail dot com!
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