- 3395 - BLACKHOLES - more complicated than we thought? Blackholes are simple objects yet so complicated for science. Blackholes are simply so much mass concentrated in so small a space that nothing can escape because of the pull of gravity. Not even the light photons can escape the pull of their immense gravity.
-------------- 3395 - BLACKHOLES - more complicated than we thought?
- Blackholes have transformed from being a mere scientific curiosity into a key element of modern astronomy. Our understanding of blackholes is now central to our understanding of our universe.
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- Astronomers have long known that Einstein's theory of gravity allowed for an object to be so massive that light itself could not escape, but they initially doubted that blackholes existed in the Universe.
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- Today, however, blackholes are recognized as a standard result of the death of very massive stars. Astronomers have made the link between supermassive central blackholes to the formation and evolution of their host galaxies with the blackhole at the center.
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- 100 years ago astronomers thought that the Universe consisted mostly of stars. They shine with the colors of light that our human eyes can see, and to most of us, the picture of an astronomer includes a telescope turned to the heavens.
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- Today, however, we now recognize that a variety of objects shine at wavelengths that our eyes cannot see, from long wavelength radio waves to extremely high-energy gamma rays. All different forms of light from the lowest frequencies to the highest frequencies. Visible light is right in the middle from 400 to 700 nanometers wavelength.
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- We now know that there are a variety of other messengers carrying to us information about the Universe. Cosmic rays are energetic sub-atomic particles, with energies well above those that particle accelerators such as the Large Hadron Collider can produce.
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- In the most extreme cases, a sub-atomic particle can hit the Earth's atmosphere with as much energy as a fast-pitch baseball. Billions of neutrinos rain upon us every second. They are born from nuclear fusion in the Sun, from distant exploding stars, from the regions near supermassive blackholes.
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- Gravitational waves constantly wash over the Earth and the Solar System. These distortions of spacetime itself are generated by colliding blackholes, and potentially by the expansion of the Universe.
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- The detection of gravitational waves, along with their direct link to merging compact objects, marks one of the major breakthroughs in astrophysics over the past 10 years. The “ngVLA” observatory will be able to resolve and observe the motion of mergers of supermassive blackholes and neutron stars, both sources of gravitational waves.
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- Blackholes are notoriously hard to detect, since they are as black as the space surrounding them. We can only pinpoint them in special circumstances, like when they pull down gas from a neighboring star or merge together, releasing a flood of gravitational waves.
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- Researchers have determined that there are potentially millions of yet-to-be-detected small blackholes in our cosmic neighborhood. This would mean that about 1% of all the matter in the universe is bound up inside blackholes.
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- To make a blackhole, you need to make stars, because blackholes come from the deaths of stars. To model galaxy evolution over the billions of years of cosmic history start with galaxies that are the homes of stars.
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- Some galaxies can steadily form new stars year after cosmic year. Others may suffer merger events that trigger a round of incredibly high star formation, only for them to burn out and produce nothing of note ever again. Another key factor is the so-called "metallicity" of a galaxy, which is a measure of the amount of elements other than hydrogen and helium inside a galaxy, astronomers call these "metals.
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- With these building blocks, the astronomers had a model of the stellar population within galaxies, telling them how many small stars, medium stars and big stars appear in the universe. Then they needed to trace the evolution of those stars.
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- Computer simulations connect the properties of a particular star (its mass and metallicity) to its lifetime and eventual demise. Only a fraction of the very largest stars produce blackholes, and those simulations tell the astronomers what percentage of a galaxy's stars go lights-out every year.
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- Next, the astronomers track the evolution of binary systems, as blackholes can feed off of sibling stars, becoming engorged on their gas in the process. Thus a blackhole formed in a binary system will end up being larger than a blackhole born solo.
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- As the blackholes age, they continue to feed on any surrounding gas. Lastly, occasionally blackholes find each other in the darkness of interstellar space and merge together.
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- Putting all the pieces together, the astronomers were able to track the population of blackholes over the course of billions of years.
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- The largest blackholes, “supermassive blackholes“, are much rarer than their smaller cousins. The researchers found that in every cubic megaparsec of space (where a megaparsec is one million parsecs, or 3.26 million light-years), our universe hosts roughly 50 million solar masses worth of blackholes. If each black hole is a few times the mass of the sun, that translates to around 10 million individual blackholes in that same volume.
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- To put that in perspective, the total amount of mass contained by blackholes is about 10% of the mass contained in stars. So for all the stars you see in the night sky, there are a lot of blackholes lurking between them.
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- Supermassive blackholes are extremely rare, with each galaxy usually hosting only one of those monsters.
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- Altogether, blackholes account for about 1% of all the baryonic ( not dark matter) matter in the cosmos today. By far most of the baryonic matter is found in “loose nebulae“.
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- Blackholes are extremely dense, with such strong gravitational attraction that even light cannot escape their grasp if it comes near enough. The term "blackhole" was coined in 1967 by American astronomer John Wheeler. After decades of blackholes being known only as theoretical objects, the first physical blackhole ever discovered was spotted in 1971.
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- Then, in 2019 the “Event Horizon Telescope” (EHT) collaboration released the first image ever recorded of a black hole. The EHT saw the blackhole in the center of galaxy M87 while the telescope was examining the event horizon, or the area past which nothing can escape from a blackhole.
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- Astronomers have identified three types of blackholes: stellar blackholes, supermassive blackholes and intermediate blackholes. When a star burns through the last of its fuel, the object may collapse, or fall into itself.
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- For smaller stars,those up to about three times the sun's mass, the new core will become a neutron star or a white dwarf. But when a larger star collapses, it continues to compress and creates a stellar blackhole.
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- Blackholes formed by the collapse of individual stars are small, but incredibly dense. One of these objects packs more than three times the mass of the sun into the diameter of a city. These stellar blackholes then consume the dust and gas from their surrounding galaxies, which keeps them growing in size.
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- Small blackholes populate the universe, but supermassive blackholes, dominate. These enormous blackholes are millions or even billions of times as massive as the sun, but are about the same size in diameter. Such blackholes are thought to lie at the center of every galaxy, including the Milky Way.
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- Once these giants have formed, they gather mass from the dust and gas around them, material that is plentiful in the center of galaxies, allowing them to grow to even more enormous sizes.
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- Supermassive blackholes may be the result of hundreds or thousands of tiny blackholes that merge together. Large gas clouds could also be responsible, collapsing together and rapidly accreting mass. A third option is the collapse of a stellar cluster, a group of stars all falling together.
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- A fourth option, supermassive blackholes could arise from large clusters of dark matter. This is a substance that we can observe through its gravitational effect on other objects; however, we don't know what dark matter is composed of because it does not emit light and cannot be directly observed.
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- Scientists once thought that blackholes came in only small and large sizes, but recent research has revealed the possibility that midsize, or intermediate, black holes (IMBHs) could exist. Such bodies could form when stars in a cluster collide in a chain reaction. Several of these IMBHs forming in the same region could then eventually fall together in the center of a galaxy and create a supermassive black hole.
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- These IMBHs may exist in the heart of dwarf galaxies (or very small galaxies). Observations of 10 such galaxies revealed X-ray activity which is common in blackholes suggesting the presence of black holes of from 36,000 to 316,000 solar masses.
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- Blackholes are also regions where gravity is strong enough to bend light, warp space and distort time. They have three "layers": the outer and inner event horizon, and the singularity.
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- The event horizon of a blackhole is the boundary around the mouth of the blackhole, past which light cannot escape. Once a particle crosses the event horizon, it cannot leave. Gravity is constant across the event horizon.
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- The inner region of a blackhole, where the object's mass lies, is known as it’s “singularity“, the single point in space-time where the mass of the blackhole is concentrated.
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- Astronomers must rely on detecting the radiation blackholes emit as dust and gas are drawn in. But supermassive blackholes, lying in the center of a galaxy, may become shrouded by the thick dust and gas around them, which can block these telltale emissions.
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- Sometimes, as matter is drawn toward a blackhole, it ricochets off the event horizon and is hurled outward, rather than being tugged into the center. Bright jets of material traveling at near-relativistic speeds are created. Although the blackhole remains unseen, these powerful jets can be viewed from great distances.
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- In 2015 the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves from merging stellar blackholes. LIGO's observations also provide insights about the direction a blackhole spins. As two blackholes spiral around one another, they can spin in the same direction or in the opposite direction.
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- There are two theories on how binary blackholes form. The first suggests that the two blackholes in a binary form at about the same time, from two stars that were born together and died explosively at about the same time. The companion stars would have had the same spin orientation as one another, so the two blackholes left behind would as well.
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- Under the second model, blackholes in a stellar cluster sink to the center of the cluster and pair up. These companions would have random spin orientations compared to one another. LIGO's observations of companion blackholes with different spin orientations provide stronger evidence for this formation theory.
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- If you fell into a blackhole, theory has long suggested that gravity would stretch you out like spaghetti, though your death would come before you reached the singularity.
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- Or, the quantum effects would cause the event horizon to act much like a wall of fire, which would instantly burn you to death.
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- Blackholes don't suck. Suction is caused by pulling something into a vacuum, which the massive blackhole definitely is not. Instead, objects fall into them just as they fall toward anything that exerts gravity, like the Earth.
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- Miniature blackholes may have formed immediately after the Big Bang. Rapidly expanding space may have squeezed some regions into tiny, dense blackholes less massive than the sun.
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- If a star passes too close to a blackhole, the star can be torn apart.
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- Astronomers estimate that the Milky Way has anywhere from 10 million to 1 billion stellar black holes, with masses roughly three times that of the sun.
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- In February, 2021, physicists revised their estimates of the properties of the cosmic monster sitting in the heart of the Cygnus X-1 system, which also happens to be the first blackhole ever confirmed to exist. Originally discovered nearly 60 years ago, the Cygnus X-1 blackhole was found to be 50% more massive than previously thought, making it 21 times the sun's mass, and spinning very close to the speed of light, setting a new record for blackhole rotation. The blackhole in Cygnus X-1 is located about 7,200 light-years away and is slowly consuming a blue supergiant companion star.
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- When a star wanders too close to the edge of a blackhole, gravitational forces will pull it apart into long strands that get sucked down the blackhole's center. This process, known as "spaghettification," produces light as the stellar material heats up via friction, allowing astronomers to capture the grisly act in all its glory.
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- In May, 2021, researchers for the first time spotted a star being shredded and devoured in this way by a black hole weighing an astounding 30 million times the mass of the sun and located in the center of a galaxy 750 million light-years from Earth.
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- In June, 2021, researchers with the Laser Interferometer Gravitational-Wave Observatory (LIGO) watched two gigantic blackholes merge into a single entity and analyzed the ripples in the fabric of space-time called gravitational waves created as the black holes spiraled toward each other at high speed.
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- The resulting blackhole's surface area was larger than the first two combined. In addition to providing amazing data, the findings help prove a 1971 conjecture from British astrophysicist Stephen Hawking known as the “blackhole area theorem“.
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- The theorem states that it is impossible for the surface area of a blackhole to decrease over time, a law Hawking derived using both Einstein's theory of general relativity as well as his understanding of entropy.
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- According to quantum mechanics, blackholes should be able to shrink and evaporate, and so it's unclear how to square that with Hawking's law that their surface area must also always increase.
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- Along with blackholes, neutron stars are one potential end result of a massive star's death, when the star explodes as a supernova and leaves behind a remnant. While LIGO had previously seen hints of potential blackhole-neutron star mergers, it wasn't until this year that two signals conclusively proved such mergers were happening.
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- Both detections occurred in January 2020, roughly 10 days apart. The first involved a blackhole with about six times the sun's mass devouring a neutron star one and a half times the sun's mass, while the second involved a blackhole about nine times the mass of the sun and a neutron star about twice as massive as the sun.
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- The intense energy emanating from the black hole creates a huge flow of gas that blows away the interstellar matter that is the material for forming stars.
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- June, 2021, astronomers showed high-speed winds being blown from a 13 billion-year-old galaxy, one nearly as old as the universe itself. This is the earliest detected example of galactic wind, which is burped out of supermassive black holes as they consume surrounding gas and dust.
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- The powerful winds, traveling at roughly 1.1 million mph propel material all over the galaxy and likely hinder star formation. This suggests that galaxies and their blackholes have an ancient and very tight bond.
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- In July, 2021, astronomers captured X-rays flaring from a supermassive blackhole in the center of a spiral galaxy called “Zwicky“, which is 1.8 billion light-years away. The researchers not only detected light coming from the front of the blackhole, but they also managed to find strange echoes of light that they initially couldn't place.
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- These lights turned out to originate from the back of the blackhole, meaning that the mammoth entity was warping the fabric of space-time so much that light photons were being pulled from one side of the blackhole to the other.
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- Despite being thought of as dark, blackholes give off large amounts of energy as they feed on surrounding material, which heats up and radiates as light. Wandering blackholes might settle in our galaxy. These rogue blackholes could make up 10% of the universe's total black hole mass.
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- In December, 2021, telescopes captured evidence of the closest blackhole pair to our own planet, a duo spinning around one another some 89 million light-years away from Earth in the constellation Aquarius.
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- The previous record-holding blackhole pair is located five times farther away than this one. Both members of the duo are heavyweights, the larger has a mass of almost 154 million suns, while the smaller is 6.3 million times more massive than our star.
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- They orbit one another with a separation of a mere 1,600 light-years, indicating that they will merge into one giant black hole 250 million years from now.
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- A tiny galaxy orbiting our own at a distance of about 820,000 light-years appears to contain an oddity. The ‘Leo I” dwarf galaxy, which is 50 times smaller than the Milky Way, hosts an outsized blackhole, one with almost the same mass as the blackhole in the Milky Way's center.
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- Astronomers are baffled as to how such a large blackhole came to reside in such a small galaxy. If blackholes do not baffle you do not understand the problem.
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January 5, 2022 BLACKHOLES - more complicated than we thought? 3386
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