How Do Scientists Study Black Holes?

26.04.2023 Grady A. Lowry 0 Comments

Don’t let the name fool you: a black hole is anything but empty space. Rather, it is a great amount of matter packed into a very small area – think of a star ten times more massive than the Sun squeezed into a sphere approximately the diameter of New York City. Intense X-ray flares thought to be caused by a black hole devouring a star. (Video) The idea of an object in space so massive and dense that light could not escape it has been around for centuries. Most famously, black holes were predicted by Einstein’s theory of general relativity, which showed that when a massive star dies, it leaves behind a small, dense remnant core. A video about black holes. Scientists can’t directly observe black holes with telescopes that detect x-rays, light, or other forms of electromagnetic radiation. We can, however, infer the presence of black holes and study them by detecting their effect on other matter nearby.

If a black hole passes through a cloud of interstellar matter, for example, it will draw matter inward in a process known as accretion. A similar process can occur if a normal star passes close to a black hole. In this case, the black hole can tear the star apart as it pulls it toward itself. As the attracted matter accelerates and heats up, it emits x-rays that radiate into space.

Recent discoveries offer some tantalizing evidence that black holes have a dramatic influence on the neighborhoods around them – emitting powerful gamma ray bursts, devouring nearby stars, and spurring the growth of new stars in some areas while stalling it in others.

One Star’s End is a Black Hole’s Beginning Most black holes form from the remnants of a large star that dies in a supernova explosion. (Smaller stars become dense neutron stars, which are not massive enough to trap light.) If the total mass of the star is large enough (about three times the mass of the Sun), it can be proven theoretically that no force can keep the star from collapsing under the influence of gravity.

However, as the star collapses, a strange thing occurs. As the surface of the star nears an imaginary surface called the “event horizon,” time on the star slows relative to the time kept by observers far away. When the surface reaches the event horizon, time stands still, and the star can collapse no more – it is a frozen collapsing object. Astronomers have identified a candidate for the smallest-known black hole. (Video) Even bigger black holes can result from stellar collisions. Soon after its launch in December 2004, NASA’s Swift telescope observed the powerful, fleeting flashes of light known as gamma ray bursts.

Chandra and NASA’s Hubble Space Telescope later collected data from the event’s “afterglow,” and together the observations led astronomers to conclude that the powerful explosions can result when a black hole and a neutron star collide, producing another black hole. Babies and Giants Although the basic formation process is understood, one perennial mystery in the science of black holes is that they appear to exist on two radically different size scales.

On the one end, there are the countless black holes that are the remnants of massive stars. Peppered throughout the Universe, these “stellar mass” black holes are generally 10 to 24 times as massive as the Sun. Astronomers spot them when another star draws near enough for some of the matter surrounding it to be snared by the black hole’s gravity, churning out x-rays in the process.

Most stellar black holes, however, are very difficult to detect. Judging from the number of stars large enough to produce such black holes, however, scientists estimate that there are as many as ten million to a billion such black holes in the Milky Way alone. On the other end of the size spectrum are the giants known as “supermassive” black holes, which are millions, if not billions, of times as massive as the Sun.

Astronomers believe that supermassive black holes lie at the center of virtually all large galaxies, even our own Milky Way. Astronomers can detect them by watching for their effects on nearby stars and gas. This chart shows the relative masses of super-dense cosmic objects. Historically, astronomers have long believed that no mid-sized black holes exist. However, recent evidence from Chandra, XMM-Newton and Hubble strengthens the case that mid-size black holes do exist.
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How does NASA study black holes?

How Is NASA Studying Black Holes? NASA is using satellites and telescopes that are traveling in space to learn more about black holes. These spacecraft help scientists answer questions about the universe.
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How did scientists study black holes?

How are black holes studied? Theorists can calculate properties of black holes based on their understanding of the universe, and such discoveries have come from a range of great thinkers, from Albert Einstein to Stephen Hawking to Kip Thorne. However, despite being so powerful, it’s hard to see something that does not emit photons, let alone traps any light that passes by.

Now, nearly a century after scientists suggested black holes might exist, the world now has tools to see them in action. Using powerful observatories on Earth, astronomers can see the, detect the ripples in space-time from, and may soon even peer at the disc of disrupted mass and energy that surrounds the black hole’s event horizon, the edge beyond which nothing can escape.

First image of the black hole at the center of the Milky Way This is the first image of Sagittarius A*, or Sgr A*, the supermassive black hole at the center of our galaxy. It’s the first direct visual evidence of the presence of this black hole. It was captured by the Event Horizon Telescope (EHT), an array which links together eight existing radio observatories across the planet to form a single Earth-sized virtual telescope.

The telescope is named after the “event horizon”, the boundary of the black hole beyond which no light can escape.
Although we cannot see the event horizon itself, because it cannot emit light, glowing gas orbiting around the black hole reveals a telltale signature: a dark central region, called a “shadow,” surrounded by a bright ring-like structure.

The new view captures light bent by the powerful gravity of the black hole, which is 4 million times more massive than our sun. The image of the Sgr A* black hole is an average of the different images that the EHT Collaboration has extracted from its 2017 observations. This result provides overwhelming evidence that the object is indeed a black hole and yields valuable clues about the workings, Astronomers reveal the first image of a black hole at the heart of our galaxy. Journey to our own black hole, Sagittarius A* Dimensional animation flying the viewer into the center of the Milky Way galaxy to the planet earth, geolocating the EHT telescopes around the planet, return to the galaxy and the S-stars orbiting the black hole in the center of our galaxy, Sgr A*. At the center of our very own Milky Way galaxy, scientists long suspected that there was a supermassive black hole, and they named this black hole Sagittarius A* (Sgr A*, pronounced “sadge-ay-star”). Media Contact email us at On April 10, 2019, the U.S. The event was the North American pillar of a simultaneous, global announcement, with NSF hosting due to its pivotal role in the discovery, having spent two decades investing in researchers, radio telescopes, and facilities that anchored the project. The content below tells the story of that image, how it was captured, and how it was revealed. National Science Foundation and Event Horizon Telescope contribute to paradigm-shifting observations of the gargantuan black hole. NSF press conference revealing first image of a black hole from Event Horizon Telescope project A global network of telescopes has been working to capture the first ever image of a black hole. A century ago, Albert Einstein predicted gravitational waves, ripples in the fabric of space-time that result from the universe’s most violent phenomena. In 2016, NSF researchers using one of the most precise instruments ever made—the NSF Laser Interferometer Gravitational-wave Observatory (LIGO)—announced the historic first detection of gravitational waves, the violent remnant of black holes colliding more than 1.3 billion years ago. The Galactic Center Group studies the black hole at the heart of the Milky Way and how it impacts its surroundings, a multi-decade effort to better understand how galaxies formed and evolved. In 2020, Ghez shared the for her discoveries, which confirmed the presence of a black hole at our galactic center. NSF’s NRAO manages several powerful radio telescopes that capture unprecedented images of the cosmos, including plasma jets and other evidence of black holes. NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab) is the United States’ flagship center for ground-based, nighttime optical and infrared astronomy. NSF’s NOIRLab manages five observatories and centers located across the globe: Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), Gemini Observatory, Kitt Peak National Observatory (KPNO) and the Vera C.

Rubin Observatory, once it becomes operational.
NSF’s Green Bank Observatory enables leading edge research at radio wavelengths by offering access to telescopes, facilities, and advanced instrumentation to the global scientific and research community.
The South Pole Telescope is a 10-meter-diameter microwave / millimeter / sub-millimeter telescope located at the U.S.

National Science Foundation’s Amundsen-Scott South Pole Station, which is the best currently operational site on Earth for mm-wave survey observations due to its stable, dry atmosphere. : How are black holes studied?
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What tools are used to study black holes?

CfA astronomers use telescopes across the entire spectrum of light, from radio waves to X-rays to gamma rays. Studying the infall of matter — called ‘accretion’ — onto black holes, using NASA’s Chandra X-ray Observatory and other telescopes.
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Why is it so hard to study black holes?

Black Holes Black holes are the most extreme manifestation of the force of gravity. When enough matter, whether from the remnants left at the end of the life of a massive star, or gas at the center of a galaxy, is compressed into a small enough volume, the force of gravity (the mutual attraction, pulling everything together) becomes so strong that no other force can match it.

The matter is pulled together and eventually becomes so compact and dense that its gravitational force becomes so strong that nothing can escape it, not even light.
At that point it is said to have formed a black hole, and the point of no return – the distance around it from which nothing can escape – is called the event horizon.

Scientists at KIPAC are working to understand many aspects of black holes: how they formed, how they grew, the exact processes by which energy is released as material falls into them, and the process by which some black holes are able to launch jets.

Black holes with masses comparable to that of the Sun (or, stellar mass black holes) are scattered through the Milky Way and neighboring galaxies, and are formed when the most massive stars come to the ends of their lives.
In addition, supermassive black holes, a million to a billion times more massive than the Sun, sit in the centers of galaxies.

This includes Sagittarius A*, which is found at the heart of our own Milky Way galaxy. Black holes are difficult to observe directly, since no light can escape from within the event horizon. Fortunately, when matter falls into a black hole, it becomes superheated and produces an intense source of light before it crosses the horizon.
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Is it possible to study a black hole?

If a black hole passes through a cloud of interstellar matter, for example, it will draw matter inward in a process known as accretion.
A similar process can occur if a normal star passes close to a black hole.
In this case, the black hole can tear the star apart as it pulls it toward itself.
As the attracted matter accelerates and heats up, it emits x-rays that radiate into space.

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One Star’s End is a Black Hole’s Beginning Most black holes form from the remnants of a large star that dies in a supernova explosion. (Smaller stars become dense neutron stars, which are not massive enough to trap light.) If the total mass of the star is large enough (about three times the mass of the Sun), it can be proven theoretically that no force can keep the star from collapsing under the influence of gravity.

Chandra and NASA’s Hubble Space Telescope later collected data from the event’s “afterglow,” and together the observations led astronomers to conclude that the powerful explosions can result when a black hole and a neutron star collide, producing another black hole.
Babies and Giants Although the basic formation process is understood, one perennial mystery in the science of black holes is that they appear to exist on two radically different size scales.

Most stellar black holes, however, are very difficult to detect. Judging from the number of stars large enough to produce such black holes, however, scientists estimate that there are as many as ten million to a billion such black holes in the Milky Way alone. On the other end of the size spectrum are the giants known as “supermassive” black holes, which are millions, if not billions, of times as massive as the Sun.

Are black holes real or theory?

Black holes seem to be the stuff of science fiction (and, in fact, have starred in many sci-fi books and movies), so it’s not uncommon for people to wonder, are black holes real? As it turns out, the answer is yes, though for a long time most scientists were convinced that black holes were purely theoretical objects.
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Do micro black holes exist?

From Simple English Wikipedia, the free encyclopedia Micro black holes are very small black holes, Because they are small, they may shrink and disappear due to Hawking radiation, They may exist in nature as primordial black holes,
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Do wormholes exist?

Wormhole theory – Wormholes were first theorized in 1916, though that wasn’t what they were called at the time. While reviewing another physicist’s solution to the equations in Albert Einstein ‘s theory of general relativity, Austrian physicist Ludwig Flamm realized another solution was possible.

He described a ” white hole,” a theoretical time reversal of a black hole, Entrances to both black and white holes could be connected by a space-time conduit. In 1935, Einstein and physicist Nathan Rosen used the theory of general relativity to elaborate on the idea, proposing the existence of “bridges” through space-time.

These bridges connect two different points in space-time, theoretically creating a shortcut that could reduce travel time and distance. The shortcuts came to be called Einstein-Rosen bridges, or wormholes. “The whole thing is very hypothetical at this point,” said Stephen Hsu, a professor of theoretical physics at the University of Oregon, told our sister site, LiveScience (opens in new tab),

“No one thinks we’re going to find a wormhole anytime soon.” Wormholes contain two mouths, with a throat connecting the two, according to an article published in the Journal of High Energy Physics (opens in new tab) (2020), The mouths would most likely be spheroidal. The throat might be a straight stretch, but it could also wind around, taking a longer path than a more conventional route might require.

Einstein’s theory of general relativity mathematically predicts the existence of wormholes, but none have been discovered to date. A negative mass wormhole might be spotted by the way its gravity affects light that passes by. Certain solutions of general relativity allow for the existence of wormholes where the mouth of each is a black hole.
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Is a black hole solid?

Black holes are certainly one of the most bizarre objects that can be found in our universe. Despite of the fact that the term black hole is probably as common as for example a planet, it is not exactly easy to tell what a black hole really is in a short, understandable and accurate way.

A very often used definition draws a black hole as a volume of space where gravity is so strong that nothing, not even light, can escape from it.
That certainly is true, but there is more to that and in what follows we try to point out some interesting features that are not explained so often.
The very first idea of an object that would not let light go first came from John Michell, an English country parson, in 1783.

If we have a gravitating cosmic body, say the Earth, we can ask how fast do we have to throw a small object in the upward direction in order for the object to escape to infinity (or at least very far away) and not return. This is a classical high-school exercise of finding the escape velocity from an object of mass M and radius R that is v=√(2GM/R).

In the case of the Earth we recover a well known value of 11.2 km/s.
Now, from the simple formula for the escape velocity we see, that for an object that is either sufficiently heavy or has sufficiently small radius the resulting velocity can be made larger than the speed of light.
Nature tells us that nothing can travel faster than light, so not only that such an object could not be seen, but there is no way anything else can escape from it because its strong gravitational force.

The question remained whether objects like that really existed. Taking our Sun as an example, it would have to be more than 500 times in size, assuming the same average density, in order for the escape velocity from its surface to exceed the speed of light.

This concept made only a little impression at Michell’s time, but came back in 1916 when Albert Einstein formulated principles of general relativity and Karl Schwarzschild found the first solution to Einstein’s equations. Einstein showed us how to think about space and time. We usually do it separately: for us space is one thing and time is something else which exists independently on space and on what is happening in it.

Such notion perfectly corresponds to our everyday experience. But according to Einstein’s relativity, we can only think like that in the low speed limit. Once things started to be more extreme, we would notice that our normal laws of physics would not hold and in order to keep the laws the same form, we are forced to link space and time into one and single concept that is since than called spacetime. In a water whirl, the speed of the flow gradually and continuously increases towards its center. At some distance from the center, the flow speed exceeds the maximum speed of the boat, and it will be unable to escape an unpleasant slide down. This distance is the boater’s personal ‘event horizon’ for the whirl, and this model is a rough analogue of a black hole.

Spacetime is so much deformed near a black hole by its mass that it only allows traveling in one direction – into the singularity.
At the event horion, space is pulled inward at the same speed light travels outward.
Credit: AiG Let’s focus on black holes now.
When astronomers speak about them, they often make an unintentional impression that they are some kind solid objects.

They are not. A black hole is a spacetime singularity that is enclosed by an event horizon, Both things are quite weird, but none of them is anything solid. The event horizon is what we usually thing is the black hole surface. In fact it is just a special place in a completely empty space, where spacetime is so extremely deformed by accumulated mass that it only allows one direction of motion – down into the singularity.

Everything that reaches this point is forced to continue further down closer to the singularity which is hidden at the center of the event horizon sphere.
The singularity is probably also nothing solid.
We say probably because nobody knows.
We do not have a good theory to describe it, we cannot probe it and event if we managed to send a robot to a black hole, there would be no way for its signals to penetrate the event horizon from the inside and reach us.

Therefore, astronomers do not care about the singularity or about what is inside the event horizon sphere. We let that worries to string theorists to dream about. Astronomers only care about what is outside of the event horizon, what they can observe. To stress the point once again, black holes are not like classical objects.

There is no surface anywhere. It is just the quality of space and time, which both behave in a peculiar way close to a strong concentration of energy in the singularity, that we call a black hole. Black holes are also one of the most simple objects in the universe we know. Imagine the Sun. It is merely impossible to describe it accurately.

It contains about 10 57 particles. For each of them we would need to record its position, velocity, quantum state, and so on. Then there are about as many photons with different energies and momenta. It all moves, interacts an evolves. No computer exists that would be capable of holding such an amount of information.

A black hole, on the other hand, is like a single elementary particle.
All the complexity of its parent star has been erased during the process of gravitational collapse and what has been left is an object that can be fully and completely characterized by three numbers only.
They are the mass, rotation and the electric charge.

In astronomy, it is common to forget about electric charge because we see that on average everything is electrically neutral in the universe and we believe that also black holes acquire as much positive charges as negative ones and they net electric charge is very very small if any.

Hence we are left with mass and rotation only. Mass is the less interesting quantity of the two. Mass is simply a scaling factor and it tells you whether the black hole is bigger or smaller, but without anything else around you would not be able to recognize any difference in spacetime distortion being two times further away from a twice as heavy black hole.

It plays a role, however, if there is mass around the black hole. Rotation is more special. First of all it may seem strange to talk about rotation in case of something that is only some distortion of spacetime rather than a real object. But the black hole was created from something.

If that was a star, for sure it was rotating before it turned into the black hole.
But from school we remember that there are certain universal conservation laws in the nature.
The most basic ones that have to do with fundamental symmetries of space and time are conservation of energy and conservation of angular momentum.

If the original star rotated, its angular momentum could not just disappear, it had to conserve. Indeed, it is in the singularity, we cannot reach it, but we know about it because it affects the surrounding spacetime structure. Astronomers often make a shortcut and say a black hole rotates rapidly.

By that statement they mean that there is a high amount of angular momentum in the singularity hidden under the event horizon that strongly affects the spacetime outside.
Surprisingly, there is a maximum limit on the amount of angular momentum the black hole can have.
The more angular momentum, the smaller is the event horizon sphere.

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If the angular momentum stored inside the black hole reached certain value, the event horizon would disappear uncovering the singularity that would become exposed to the word. Such a situation is called a naked singularity and because it would cause a lot of trouble we think nature prevents it to happen.

We call this principle cosmic censorship, In fact, the argument is more involved than simply postulate that it cannot happen because it is not convenient, for instance it would take an infinite amount of time to spin up a black hole and reach the maximal value. For us the important thing is the existence of maximal value of the contained angular momentum.

Astronomers usually take that value as a scaling factor and measure the angular momentum of black holes in the units of their respective maximal value (it depends on mass). Such measure is then called spin and it can have value from zero (for a non-rotating black hole) to one (spin greater than one belongs to naked singularities). A number of interesting things happen close to the horizon. One thing you would notice is that Euclidean geometry does not apply. If you measured circumference of two nearby circular orbits and divided both measurements by 2π to recover their respective radii, you would find out that the difference in the two radii measured that way is less than the difference in radial distances that is measured directly e.g.

Using light signal sent between the two orbits. A similar feature applies to time interval measurements. Time intervals that are measured at smaller radii (orbits closer to the black hole) appear to last longer than intervals measured by the same technique further away. Both effects are a consequences of distortion of both space and time due to strong gravity.

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What math is used for black holes?

Amazingly enough, many aspects of black holes can be understood by using simple algebra and pre-algebra mathematical skills.
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What type of physics studies black holes?

A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape its event horizon, The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.

The boundary of no escape is called the event horizon,
Although it has a great effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity.
In many ways, a black hole acts like an ideal black body, as it reflects no light.
Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass.

This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly. Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace,

In 1916, Karl Schwarzschild found the first modern solution of general relativity that would characterize a black hole. David Finkelstein, in 1958, first published the interpretation of “black hole” as a region of space from which nothing can escape. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity.

The discovery of neutron stars by Jocelyn Bell Burnell in 1967 sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality. The first black hole known was Cygnus X-1, identified by several researchers independently in 1971.

Black holes of stellar mass form when massive stars collapse at the end of their life cycle.
After a black hole has formed, it can grow by absorbing mass from its surroundings.
Supermassive black holes of millions of solar masses ( M ☉ ) may form by absorbing other stars and merging with other black holes.

There is consensus that supermassive black holes exist in the centres of most galaxies, The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Any matter that falls onto a black hole can form an external accretion disk heated by friction, forming quasars, some of the brightest objects in the universe.

Stars passing too close to a supermassive black hole can be shredded into streamers that shine very brightly before being “swallowed.” If other stars are orbiting a black hole, their orbits can determine the black hole’s mass and location.
Such observations can be used to exclude possible alternatives such as neutron stars.

In this way, astronomers have identified numerous stellar black hole candidates in binary systems and established that the radio source known as Sagittarius A*, at the core of the Milky Way galaxy, contains a supermassive black hole of about 4.3 million solar masses.
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How did Einstein predict black holes?

Albert Einstein was right (again): Astronomers have detected light from behind a supermassive black hole – ABC News Over a century ago, Albert Einstein predicted that the gravitational pull of black holes were so strong that they should bend light right around them. Black holes don’t emit light, they trap it; and ordinarily, you can’t see anything behind a black hole.

Scientists have seen light bouncing off the back of a supermassive black hole for the first time
The warped light was detected as faint flashes of X-rays emitting from a supermassive black hole 800 million light years away
The findings confirm a prediction Albert Einstein made over a century ago

But it seems Einstein’s theory was right.
For the first time, astronomers have caught a glimpse of light being reflected — or “echoing” — from behind a supermassive black hole, 800 million light years away from Earth.
These “echoes” were in the form of X-ray flashes, according to a study published on Thursday in,
While scientists have seen before, this is the first time they have been able to see the phenomenon happening from the other side.
“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” said study co-author Dan Wilkins, an astrophysicist at Stanford University.

“The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself.”
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What degree do I need to study black holes?

An astronomy and astrophysics major studies how the universe formed and the stars, planets, black holes, dark matter and galaxies that exist within it. With a curriculum centered on physics and mathematics, astronomy majors also use data to observe and model the universe. Students may go on to pursue advanced degrees or work in a variety of science-related fields.
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Would a black hole be scary?

We are in absolutely no danger from black holes. They’re a bit like tigers – it’s a bad idea to stick your head in their mouth, but you’re probably not going to meet one on your way to the shops. Unlike tigers, black holes don’t hunt. They’re not roaming around space eating stars and planets.
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What is a black hole scientist called?

He was the last physicist whose unique profile transcended the boundaries of science to become, like Einstein, an icon of popular culture. His image has remained linked to the field that accounted for the bulk of his work—black holes. The discoveries of Stephen Hawking (8 January 1942 – 14 April 2018) shone light on the darkness of these mysterious astronomical objects, but at the same time raised questions that will continue to trouble scientists for decades to come.

In the mind of the public, black holes are often imagined as huge cosmic vacuum cleaners that suck up everything in their path, including light. This is an evocative but incorrect idea. A black hole is not and does not create a vacuum, but quite the opposite; it attracts through the effect of gravity, because the density of its mass is so enormous.

It follows that we should have nothing to fear if the Sun were to be replaced by a black hole of the same mass—though our world would be much colder and darker, the planets would continue to orbit undisturbed because the mass of the black hole would be equivalent to that of the Sun.

The existence of black holes stems from the theory of general relativity published by Albert Einstein in 1915, and the subsequent work of Robert Oppenheimer, Karl Schwarzschild, Subrahmanyan Chandrasekhar and others.
Space and time form a fabric that is curved by mass, like a trampoline.
A black hole is a ball so heavy that it has at its centre a singularity, a region so infinitely dense that it collapses the bottomless trampoline.

Any object we place nearby will tend to fall towards the ball, so the gravitational effect of the black hole is felt in its surroundings. Astrophysicists have been able to identify many such black holes by discovering cosmic objects orbiting around an apparent nothingness; this gravitational pull reveals the presence of something that is otherwise completely invisible.
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Has anyone gone into a black hole before?

5. What would happen if you fell into a black hole? – It certainly wouldn’t be good! But what we know about the interior of black holes comes from Albert Einstein’s General Theory of Relativity. For black holes, distant observers will only see regions outside the event horizon, but individual observers falling into the black hole would experience quite another “reality.” If you got into the event horizon, your perception of space and time would entirely change.

At the same time, the immense gravity of the black hole would compress you horizontally and stretch you vertically like a noodle, which is why scientists call this phenomenon (no joke) “spaghettification.” Fortunately, this has never happened to anyone — black holes are too far away to pull in any matter from our solar system.

But scientists have observed black holes ripping stars apart, a process that releases a tremendous amount of energy. NASA’s Chandra X-ray observatory detected record-breaking wind speeds coming from a disk around a black hole. This artist’s impression shows how the strong gravity of the black hole, on the left, is pulling gas away from a companion star on the right.
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Is spaghettification a real thing?

In astrophysics, spaghettification is the tidal effect caused by strong gravitational fields. When falling towards a black hole, for example, an object is stretched in the direction of the black hole (and compressed perpendicular to it as it falls).
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Are black holes infinite?

Myth: black holes suck everything in – Perhaps the most prevalent myth about black holes is that they ‘suck’ matter towards them, like really powerful vacuum cleaners. Don’t worry! They’re not going to eventually consume everything in the universe, and you don’t need to be afraid of them unless you plan on travelling VERY close.

Why? Well, even though black holes are extreme in many ways, they don’t have infinite mass—and it’s mass that determines the force of their gravity. Some black holes—known as stellar black holes —have about the amount of mass that very massive stars do. So, just as objects can orbit massive stars without falling in, the same is true of black holes.

You could happily orbit a black hole forever. Once you get close enough, the story’s different, and gravity will guide you in. But that’s the same as any massive object, like a planet or star.
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Are we living inside a black hole?

One of the biggest existential questions that has puzzled humanity for as long as humans have been around is simply, “Where did all this come from?” After countless centuries of wondering and speculating, the 20th century brought with it our first scientific answers to that question.

We learned that distant objects in the Universe are speeding away from one another: evidence that our Universe is expanding.
We discovered that more distant galaxies appear younger, less massive, and with greater rates of star formation: evidence that our Universe evolves with time.
And we discovered a near-uniform background of blackbody radiation: evidence of an early, hot, dense, radiation-dominated state.

All of these puzzle pieces, when put together, indicate that our Universe originated from a hot Big Bang some 13.8 billion years ago. But our Universe has a very curious property that not everyone appreciates. If you add up the mass and energy of all the particles contained within the visible Universe, you can ask the question, “How big would the event horizon of a black hole with this mass be?” And the answer, perhaps surprisingly, is very close to the actual horizon size of the observable Universe.

Additionally, there’s another related idea, made famous by Stephen Hawking, that each time we create a black hole in our Universe, it could give rise to a “baby Universe” that’s only accessible to an observer that crosses inside that black hole’s event horizon. Could our Universe, then, actually have been spawned by a black hole that was created in some sort of grand “parent Universe,” and do we give birth to a new Universe each time a new black hole is created? It’s a fascinating idea worth exploring.

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Here’s what the science, at present, has to say about it. Even for a complicated entity like a massive, rotating black hole (a Kerr black hole), once you cross the (outer) event horizon, regardless of what type of matter or radiation you’re composed of, you’ll fall towards the central singularity and add to the black hole’s mass.

Credit : Andrew Hamilton/JILA/University of Colorado) The defining feature of a black hole is the existence of an event horizon: a boundary that tells a very different story for an object outside of it versus one inside of it. Outside of a black hole’s event horizon, any object will experience its gravitational effects, as the space will be curved by the black hole’s presence, but it can still escape.

If it moves fast enough or accelerates quickly enough in the proper direction, it won’t necessarily fall into the black hole, but it could break free of the black hole’s gravitational influence. Once an object crosses over to the other side of the event horizon, however, it’s immediately doomed to be subsumed into the black hole’s central singularity. One of the most important contributions of Roger Penrose to black hole physics is the demonstration of how a realistic object in our Universe, such as a star (or any collection of matter), can form an event horizon and how all the matter bound to it will inevitably encounter the central singularity.

normal matter, made from protons, neutrons, and electrons,
neutrinos, ghostly fundamental particles that rarely interact with normal matter,
dark matter, which dominates the Universe’s mass but has so far eluded direct detection efforts,
photons, or particles of light, which carry energy from every electromagnetic event throughout cosmic history,
and gravitational waves, which are created every time a mass moves and accelerates through the curved fabric of spacetime.

At the farthest limits of what our instruments can possibly detect, we can see up to about 46 billion light-years away in all directions. If you add up all the energy from all of these forms throughout the entire observable Universe, you can arrive at an equivalent “mass” for the Universe using Einstein’s most famous relation: E = mc², Nearby, the stars and galaxies we see look very much like our own. But as we look farther away, we see the Universe as it was in the distant past: less structured, hotter, younger, and less evolved. Measuring the Universe at different epochs helps us understand all the different forms of matter and energy present within it, including normal matter, dark matter, neutrinos, photons, black holes, and gravitational waves.

Credit : NASA/ESA/A. Feild (STScI)) Then, if you like, you can ask a rather profound question: if the entire Universe were compressed into a single point, what would happen? The answer is the same as it would be if you compressed any large-enough collection of mass or energy into a single point: it would form a black hole.

What’s remarkable about Einstein’s theory of gravity is that if this collection of mass-and/or-energy isn’t charged (electrically) and isn’t rotating or spinning (i.e., without angular momentum), the total amount of mass is the only factor that determines how large the black hole is: what astrophysicists call Schwarzschild radius.

Remarkably, the Schwarzschild radius of a black hole with the mass of all the matter in the observable Universe is almost exactly equal to the observed size of the visible Universe! That realization, on its own, seems like a remarkable coincidence, raising the question of whether our Universe might actually somehow be the interior of a black hole.

But that’s only the beginning of the story; as we dive deeper, things get even more interesting. When a black hole forms, the mass and energy collapses down to a singularity. Similarly, continuing to extrapolate the expanding Universe backwards in time leads to a singularity when temperatures, densities and energies are high enough. Could these two phenomena be connected? ( Credit : NASA/CSC/M.Weiss) In the mid-1960s, a discovery revolutionized our concept of the Universe: a uniform, omnidirectional bath of low-energy radiation appeared from all locations in the sky.

This radiation had the same temperature in all directions, now determined to be 2.725 K, just a few degrees above absolute zero. The radiation had a practically perfect blackbody spectrum, as though it had a hot, thermal origin, and appeared identical to within 1-part-in-30,000 no matter where you looked in the sky.

This radiation — originally called the primeval fireball and now known as the cosmic microwave background — represented critical evidence that our Universe is expanding and cooling because it was hotter and denser in the past. The farther back we extrapolate, the smaller, more uniform, and more compact things were. When matter collapses, it can inevitably form a black hole. Penrose was the first to work out the physics of the spacetime, applicable to all observers at all points in space and at all instants in time, that governs a system such as this. His conception has been the gold standard in General Relativity ever since.

( Credit : J. Jarnstead/Royal Swedish Academy of Sciences) Something remarkable happens when you look at the equations that govern a black hole as well. If you start just outside the event horizon and escape to an infinite distance away from the black hole, you’ll find that your distance ( r ) goes from R, the Schwarzschild radius, to infinity: ∞.

On the other hand, if you start just inside the event horizon and track your distance from the black hole to the central singularity, you’ll find that same distance ( r ) instead goes from R, the Schwarzschild radius, to zero: 0. Big deal, right? No, it actually is a big deal, for the following reason: if you examine all the properties of space outside of a black hole’s event horizon, from R to ∞, and compare them to all the properties of space inside the black hole’s event horizon, from R to 0, they are identical at every single point. Subscribe for counterintuitive, surprising, and impactful stories delivered to your inbox every Thursday It’s almost like taking a spherical orb that’s 100% reflective — a perfect mirror — and noticing that the entirety of the Universe that’s located outside of that sphere is now contained, albeit distorted, in the mirror image that’s reflected on the sphere’s surface. Just as the entire Universe located outside of a spherical mirror will be encoded on the reflection in the mirror’s surface, it’s possible that what occurs in the interior of a black hole encodes an entirely new Universe on the inside. It’s possible that this is relevant to our Universe as well.

( Credit : Antti T. Nissinen/flickr) As our understanding of the Universe has improved and been refined over the past few decades, two new discoveries have rocked the foundations of cosmology. The first was cosmic inflation: instead of arising from a singularity, it now appears that the Universe was set up by a rapid, relentless state of constant, exponential expansion that preceded the hot Big Bang.

It’s as though there were some sort of field that provided an energy inherent to space itself, causing the Universe to inflate, and only when inflation ended did the hot Big Bang begin. The second was dark energy: as the Universe expands and becomes less dense, distant galaxies start to recede from us at an accelerating rate.

Once again — albeit, with a much smaller magnitude — the Universe behaves as though there’s some sort of energy inherent to space itself, refusing to dilute even as the expansion of space continues.
People have speculated that there might be a connection for as long as inflation and dark energy have both been around.

The fact that there’s a fundamental difference between the expansion rate of the Universe that you infer depending on which of the two classes of methods you use to measure it only strengthens that conjecture. One potential explanation that stubbornly persists for reconciling this discrepancy is that there was a stronger form of dark energy early on : one that existed after the end of inflation but decayed away before the cosmic microwave background scattered off of the primeval plasma for the final time. During the earliest stages of the Universe, an inflationary period set up and gave rise to the hot Big Bang. Today, billions of years later, dark energy is causing the expansion of the Universe to accelerate. These two phenomena have many things in common, and may even be connected, possibly related through black hole dynamics.

Credit : C.-A.
Faucher-Giguere, A.
Lidz, and L.
Hernquist, Science, 2008) What might that connection be? Once again, black holes could be the answer.
Black holes gain mass as material falls into them, and decay, losing mass, via Hawking radiation.
As the size of the event horizon changes, is it possible that this changes the “energy” inherent to the fabric of space to an observer located inside the event horizon? Is it possible that what we perceive as cosmic inflation marks the creation of our Universe from an ultramassive black hole? Is it possible that dark energy is somehow connected to black holes as well? And does this mean that, as astrophysical black holes have formed within our Universe, that each one gives rise to its own “baby Universe” somewhere inside of it? These speculations have been around for many decades, and although we lack a definitive or provable conclusion, there are certainly some mathematically compelling pieces of evidence that suggest a link,

Nevertheless, many models and ideas abound, and this line of thought continues to be compelling to many who research black holes, thermodynamics and entropy, General Relativity, as well as the beginning and end of the Universe. For approximately 10 years, Roger Penrose has been touting extremely dubious claims that the Universe displays evidence of a variety of features that are consistent with our Universe colliding with and being “bruised by” whatever occurred prior to the Big Bang.

Reproduce all the successes, like the already-observed phenomena, that the inflationary hot Big Bang has already successfully accounted for.
Explain and/or account for observed phenomena that the prevailing theory cannot.
Make new predictions that differ from those predicted by the current leading model, that we can then go out and test.

Perhaps the most famous attempt at this is Roger Penrose’s Conformal Cyclic Cosmology (CCC), which does make a unique prediction that differs from the standard cosmological models: the existence of Hawking points, or circles of unusually low temperature variance in the cosmic microwave background. From outside a black hole, all the infalling matter will emit light and is always visible, while nothing from behind the event horizon can get out. But if you were the one who fell into a black hole, your energy could conceivably re-emerge as part of a hot Big Bang in a newborn Universe.

Credit : Andrew Hamilton, JILA, University of Colorado) There’s a lot to like about the idea that there’s a connection between black holes and the birth of Universes, from both physical and mathematical points of view.
It’s plausible that there’s a connection between the birth of our Universe and the creation of an extremely massive black hole from a Universe that existed before our own; it’s plausible that every black hole that’s been created in our Universe has given rise to a new Universe within it.

What’s missing, unfortunately, is the key step of a uniquely identifiable signature that could tell us whether this is the case or not. That’s one of the most difficult steps for any theoretical physicist: to determine the imprint of a new idea on our observable Universe, distinguishing that new idea from our old, prevailing ones.

Until we successfully take that step, work will likely continue on these ideas, but they will only remain speculative hypotheses. We don’t know whether our Universe was birthed by the creation of a black hole, but at this point, it’s a tantalizing possibility that we would be foolish to rule out. An earlier version of this article, previously published in January 2021, has been removed and replaced with this version by Dr.

Ethan Siegel.
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Are black holes hot?

Temperature – The more massive a black hole, the colder it is. Stellar black holes are very cold: they have a temperature of nearly absolute zero – which is zero Kelvin, or −273.15 degrees Celsius. Supermassive black holes are even colder. But a black hole’s event horizon is incredibly hot. The gas being pulled rapidly into a black hole can reach millions of degrees.
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How did scientists discover the first black hole?

In 1974 American astronomers Bruce Balick and Robert Brown pointed radio telescopes in Green Bank, W.Va., at the center of the Milky Way and discovered a dim speck they suspected was our galaxy’s central black hole. They found it in a slice of sky, known as Sagittarius A, within the constellation Sagittarius.
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Who first studied black holes?

A black hole is a volume of space where gravity is so strong that nothing, not even light, can escape from it. This astonishing idea was first announced in 1783 by John Michell, an English country parson.
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Grady A. Lowry