Black Holes | Universe Today

The search is on to detect the first evidence of gravitational waves travelling around the cosmos. How can we do this? The Laser Interferometer Gravitational-Wave Observatory (LIGO) uses a system of laser beams fired over a distance of 4 km (2.5 miles) and reflected back and forth by a system of mirrors. Should a gravitational wave pass through the volume of space-time surrounding the Earth, in theory the laser beam will detect a small change as the passing wave slightly alters the distance between mirrors. It is worth noting that this slight change will be small; so small in fact that LIGO has been designed to detect a distance fluctuation of less than one-thousandth of the width of a proton. This is impressive, but it could be better. Now scientists think they have found a way of increasing the sensitivity of LIGO; use the strange quantum properties of the photon to "squeeze" the laser beam so an increase in sensitivity can be achieved…
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Astronomers now know that essentially every galaxy has a supermassive black hole at its center. When the black hole is actively feeding on material, the surrounding region can blaze brightly - this is a quasar, aka an active galaxy. The Hubble Space Telescope has been used to image a set of exotic active galaxies, known as post-starburst quasars.
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According to Einstein's theory of general relativity, black holes are regions of space where gravity is so strong that not even light can escape. And in the 1970's physicist Stephen Hawking asserted that any information sucked inside a black hole would be permanently lost. But now, researchers at Penn State have shown that information can be recovered from black holes.
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Looking for Hawking Radiation in space is likely impossible with our current technology. But scientists here on Earth recently used flowing water to simulate a black hole and create event horizons, testing Stephen Hawking's famous prediction that the event horizon creates particles and anti-particles.
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Playing with black holes is a risky business, especially for a star that is unlucky enough to be orbiting one. Assuming an unfortunate star hasn't already had all of its hydrogen fuel and other component elements stripped from its surface, the powerful tidal forces will have some fun with the doomed stellar body. First the star will be stretched out of shape and then it will be flattened like a pancake. This action will compress the star generating violent internal nuclear explosions, and shockwaves will ripple throughout the tormented stellar plasma. This gives rise to a new type of X-ray burst, revealing the sheer power a black hole's tidal radius has on the smaller binary sibling. Sounds painful…
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Question: What is on the other side of a black hole?

Answer: There is no other side.

Science fiction has populated the idea that a black hole serves a portal to another world. If you could pass through, where does a black hole go? Perhaps you'll come to some other dimension, or re-emerge from some other part of the Universe?

No, a black hole only leads to death, for you, your spaceship, and another else that's unlucky enough to fall in.

Imagine you fell into a star like our Sun, there would be no question what would happen to you. The intense heat, gravity and pressure would kill you. If you compress more than 5x the mass of the Sun into a tight little area, you get a black hole. But the gravity, heat and pressure are all still there, just much more intense.

If you actually fell into a black hole, the tidal forces pulling at you are so extreme that the force on your feet is dramatically stronger than the force at your head. You would be stretched out and torn into pieces, and then those pieces would be torn into pieces. You would eventually be pulled into a stream of atoms, winding their way down to the surface of the black hole. For this process, scientists have a technical term: spaghettification.

Let's say you could survive this journey. Where does the black hole lead? No where. All of the mass of the star that came before the black hole is still there, pulling at you with all its gravity. This intense gravity would tear every molecule apart, and all the atoms. Protons and electrons would be crushed together to create neutrons, and then these would be crushed together even further into some kind of exotic form of superdense matter.

It's even possible that the heart of a black hole is single point of infinitely small size, containing the mass of many stars. This black hole is not a portal to anywhere, it's just a final destination.

Here's an article I did about how to maximize your time while falling into a black hole.

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For the first time, the most extreme collision to occur in the cosmos has been observed. Galaxies are known to hide supermassive black holes in their cores, and should the galaxies collide, tidal forces will cause massive disruption to the stars orbiting around the galactic cores. If the cores are massive enough, the supermassive black holes may become trapped in gravitational attraction. Do the black holes merge to form a super-supermassive black hole? Do the two supermassive black holes spin, recoil and then blast away from each other? Well, it would seem both are possible, but astronomers now have observational evidence of a black hole being blasted away from its parent galaxy after colliding with a larger cousin.
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The cores of galaxies contain supermassive black holes, containing hundreds of millions of times the mass of Sun. As matter falls in, it chokes up, forming a super hot accretion disk around the black hole. From this extreme environment, the black hole-powered region spews out powerful jets of particles moving at the speed of light. Astronomers have recently gotten one of the best views at the innermost portion of the jet.
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The light echo of an X-ray flare from the nucleus of a galaxy has been observed. The flare almost certainly originates from a single star being gravitationally ripped apart by a supermassive black hole in the galactic core. As the star was being pulled into the black hole, its material was injected into the black hole accretion disk, causing a sudden burst of radiation. The resulting X-ray flare emission was observed as it hit local stellar gases, producing the light echo. This event gives us a better insight to how stars are eaten by supermassive black holes and provides a method to map the structure of galactic nuclei. Scientists now believe they have observational evidence for the elusive molecular torus that is thought to surround active supermassive black holes.
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Question: Why are Black Holes in the Middle of Galaxies?

Answer: The black holes you're thinking of are known as supermassive black holes. Stellar mass black holes are created when a star at least 5 times larger than the Suns out of fuel and collapses in on itself forming a black hole. The supermassive black holes, on the other hand, can contain hundreds of millions of times the mass of a star like our Sun.

Astronomers are now fairly certain that these supermassive black holes are at the heart of almost every galaxy in the Universe. Furthermore, the mass of these black holes is somehow tied to the mass of the rest of the galaxy. They grown in tandem with each other.

When large quantities of material falls into the black hole, it chokes up, unable to get consumed all at once. This "accretion disk" begins to heat up and blaze brightly in many different wavelengths, including X-rays. When supermassive black holes are actively feeding, astronomers call these quasars.

So how do these black holes get there in the first place? Astronomers aren't sure, but it could be that the dark matter halo that surrounds every galaxy serves to focus and concentrate material as the galaxy was first forming. Some of this material became the supermassive black hole, while the rest became the stars of the galaxy. It's also possible that the black hole formed first, and collected the rest of the galaxy around it.

Astronomers just don't know.

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Our Milky Way's black hole is quiet - too quiet - some astronomers might say. But according to a team of Japanese astronomers, the supermassive black hole at the heart of our galaxy might be just as active as those in other galaxies, it's just taking a little break. Their evidence? The echoes from a massive outburst that occurred 300 years ago.
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The consequences of two black holes colliding may be huge, the energy produced by such a collision could even be detected by observatories here on Earth. Ripples in space-time will wash over the Universe as gravitational waves and are predicted to be detected as they pass through the Solar System. Taking this idea one step further, what would happen if three black holes collide? Sound like science fiction? Well it's not, and there is observational evidence that three black holes can cluster together, possibly colliding after some highly complex orbits that can only be calculated by the most powerful computers available to researchers…
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According to new research, a galaxy with a quasar in the middle is not a good place to grow up. As active galactic nuclei (AGN) evolve, they pass through a "quasar phase", where the accretion disk surrounding the central black hole blasts intense radiation into space. The quasar far outshines the entire host galaxy. After the quasar phase, when the party is over, it is as if there is no energy left and star formation stops.
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Omega Centauri is a strange thing. It's been classified as a star, then a nebula, then a globular cluster and now it's thought to be a dwarf galaxy missing its outer stars. Why is it in such a mess? How can this oddball galaxy be explained? New research suggests it has an intermediate-black hole living in its core, giving astronomers the best idea yet as to where supermassive black holes come from. Omega Centauri might hold one of the most profound secrets as to how the largest objects in the observable universe are born…
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Black holes seem to have no upper limit; some weigh in at hundreds of millions of times the mass of the Sun. But how small can they be? Astronomers have discovered what they think is the least massive black hole ever seen, with a mere 3.8 times the mass of the Sun, and a diameter of only 25 km (15 miles) across.
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Primordial black holes are remnants of the Big Bang and they are predicted to be knocking around in our universe right now. If they were 10¹²kg or bigger at the time of creation, they have enough mass to have survived constant evaporation from Hawking radiation over the 14 billion years since the beginning of the cosmos. But what happens when the tiny black hole evaporates so small that it becomes so tightly wrapped around the structure of a fifth dimension (other than the "normal" three spatial dimensions and one time dimension)? Well, the black hole will explosively show itself, much like an elastic band snapping, emitting energy. These final moments will signify that the primordial black hole has died. What makes this exciting is that researchers believe they can detect these events as spikes of radio wave emissions and the hunt has already begun…
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It is widely accepted that supermassive black holes (SMBHs) sit in the centre of elliptical galaxies or bulges of spiral galaxies. They suck in as much matter as possible, generating blasts of radiation. Stars, gas and everything else nearby forms a compact "halo" and then falls to a gravitationally enforced death spiral. The greedy nature and the sheer size of these black holes have led to the idea that dark matter may supply (or may have supplied) the SMBH with some mass during its evolution. But could it be that dark matter may not be significantly involved after all? This might be one cosmic phenomenon dark matter can't be blamed for…
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As galaxies merge together, you might be wondering what happens with the supermassive black holes that lurk at their centres. Just imagine the forces unleashed as two black holes with hundreds of millions of times the mass of the Sun come together. The answer will surprise you. Fortunately, it's an event that we should be able to detect from here on Earth, if we know what we're looking for.
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Primordial black holes (PBHs) are getting mischievous again. These artefacts from the Big Bang could be responsible for hiding inside planets or stars, they may even punch a neat, radioactive hole through the Earth. Now, they might start playing interplanetary billiards with asteroids in our solar system.

Knocking around lumps of rock may not sound very threatening when compared with the small black holes' other accolades, but what if a large asteroid was knocked off course and sent in our direction? This could be one of the most catastrophic events yet to come from a PBH passing through our cosmic neighborhood…
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We can all guess what would happen should a massive black hole drift into our solar system… there wouldn't be much left once the intense gravitational pull consumes the planets and starts sucking away at our Sun. But what if the black hole is small, perhaps a left over remnant from the Big Bang, passing unnoticed through our neighborhood, having no observable impact on local space? What if this small singularity falls in the path of Earths orbit and hits our planet? This strange event has been pondered by theoretical physicists, understanding how a small black hole could be detected as it punches a neat hole though the Earth…
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Researchers at St. Andrews University, Scotland, claim to have found a way to simulate an event horizon of a black hole - not through a new cosmic observation technique, and not by a high powered supercomputer… but in the laboratory. Using lasers, a length of optical fiber and depending on some bizarre quantum mechanics, a "singularity" may be created to alter a laser's wavelength, synthesizing the effects of an event horizon. If this experiment can produce an event horizon, the theoretical phenomenon of Hawking Radiation may be tested, perhaps giving Stephen Hawking the best chance yet of winning the Nobel Prize.
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Gravitational waves are predicted by Einstein's 1916 general theory of relativity, but they are notoriously hard to detect and it's taken many decades to come close to observing them. Now, with the help of a supercomputer named SUGAR (Syracuse University Gravitational and Relativity Cluster), two years of data collected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) will be analyzed to find gravitational waves. Once detected, it is hoped that the location of some of the Universes most powerful collisions and explosions will be found, perhaps even hearing the distant ringing of celestial black holes…
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It's one of the big mysteries in astronomy. There are stellar mass black holes and the supermassive variety, but nothing in between. Where are all the intermediate mass black holes? Astronomers theorize that they could be located in globular star clusters, but nothing definitive has turned up yet. A team of researchers think they've come up with a new way to detect intermediate black holes - a way to see them for billions of light-years.
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Occasionally, stars minding their own business around the supermassive black hole at the center of our galaxy get chucked out of the Milky Way, never to return. Fraser wrote about the discovery of two of these exiled stars, hurling away at the mind-blowing speed of over 1 million miles an hour. A recent study of another shows that not all of them originate in the center of our own galaxy.

New results from astronomers at the Carnegie Institute show that one star rocketing away from the Milky Way hearkens from the Large Magellanic Cloud, our neighboring galaxy. There have been ten such hypervelocity stars discovered, but where this one came from was quite a conunudrum. Read more…

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Supermassive black holes are thought to lurk at the heart of most galaxies. Scientists have long believed that only the galaxies with thick central bulges could pull together enough mass for a supermassive black hole to form. But NASA's Spitzer Space Telescope has turned up evidence that even skinny galaxies, with no central bulge, can still form these galactic monsters.
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