How does a quark-gluon plasma exsist, when it's density is enough to support a star? No black hole creation?
600386
You don't need a black hole to be able hold itself together through gravity. Just look at the earth or the moon for example. They are nowhere near as dense as a black hole, yet they support themselves gravitationally.
205867
There weren't any. Look up the phrase "quark-gluon plasma".\n\nIt's like asking how much frozen water exists in the sun.
330240
A black hole isn't necessarily big or heavy. Any mass M which is compressed to \n\nSchwarzschild Radius: R = 2*G*M/c²\n\ngravitational constant: G = 6,6742/10^11 m³/(kg*m²)\nspeed of light: c = 2,9979*10^8 m/s\n\n\nwill collapse and form a black hole, theoretically. If you have such a thing and want to carry it around you have to isolate it from surronding matter because everything touching the event horizont R will fall into it. But that's science fiction. Rumours say that romulans use tiny black holes for their warp drives and call them quantum singularities.\n\nHawking Radiation\nhttp://en.wikipedia.org/wiki/Hawking_radiation
585565
Spectroscopy (splitting the light into its constituent colors) and photometry (counting up how much light there is).  We can measure how far away they are via redshift, and from that and brightness measurements calculate their absolute luminosity (how much energy it puts out per second). The size of the emitting area can have an upper limit placed on it by watching how fast it varies in brightness.  (Approximately the speed of light over the brightness change timescale).  \n\nSo, you are emitting "x" amount of energy in a volume of "y" size.  The number of stars necessary to produce that sort of energy collectively would have a mass large enough that this superdense cluster would be inside of its own Schwarzschild radius (ie be a black hole).  \n\nSo you need some more efficient way to produce energy than fusion in stars.  The only astrophysical phenomenon known to do that is the rapid loss of a large fraction of  gravitational potential of mass (drop something onto something dense enough that it would reach an appreciable fraction of the speed of light. As it interacts with other matter on the way in, it heats up and glows.)  This requires either black hole or neutron star type gravity.\n\nI suppose you could hypothesize a dense cluster of a zillion neutron stars all accreting matter, but that is pretty contrived compared to a single large blackhole.  You can probably show that their accretion disks would result in enough drag as they zipped around one another (and consequently through one another's accretion disks) in this small volume that they would all be coalescing and collapsing into blackholes in a pretty short timescale anyway.\n\nIn short, nothing so small and so bright could be anything BUT an accreting supermassive blackhole.
1034163
A Neutron star is in the phase before the black hole where the density is much less than that of a black hole where it is infinite. Neutron stars can have escape velocities and no event horizon. A neutron star is also a star with a density of  8×1013 to 2×1015 g/cm³ instead of infinite.
9631
I suppose you are referring to galaxies composed entirely or at least mostly of antimatter. None have been observed. If there were any, it would certainly be coming into contact with large amounts of matter at some sort of boundary. At that point, the collisions of the two would set off gigantic amounts of gamma rays, which we would be able to see. These have not, however, been observed. This is likely due to the fact that, for some reason as yet unknown, the amount of matter has increased hugely in the universe relative to antimatter since the big bang.
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As matter spirals into a black hole, it speeds up more and more until it approaches the speed of light, most researchers agree. The matter -- stars, gas, dust -- becomes superheated, and is called plasma. \n\nBut not everything heading toward a black hole goes in. Some energy is squirted out in two opposing jets, along the axis of the black hole's rotation. \n\nAstronomers have detected these ejection jets in radio waves and X-rays. They suspect that the infalling matter and the outflowing energy are related, all having to do with the violent interactions that occur right where matter reaches the point of no return, a sphere of influence known as a black hole's event horizon.\n\nStrong magnetic fields play into this interaction. The research  the scientists combined data about plasma swirling into a black hole with knowledge about how gravity and magnetic fields would affect it.\n\n"In this case, jets of pure electromagnetic energy are ejected by the magnetic field along the north and south poles, above the black hole," said David Meier, an astrophysicist at NASA's Jet Propulsion Laboratory who worked on the study. "The jets contain energy equivalent to the power of the Sun, multiplied ten billion times and then increased another one billion times."
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As a star gets older it fuses lighter elements into heavier ones. Every moment of a stars life is a delicate balance of the energy from the fusion reactions tryong to blow the star apart while the gravity of the star's mass tries to crush it inward.\n\nThere will be a point in every star's existance that the energy of nuclear fusion is no longer enough to maintain the balance and a new equilibrium of sought. When our sun runs out of hydrogen in roughly 5 billion years it will have to switch to helium and become a red giant star for example. When the star runs out of fusionable elements, it "dies". Depending on how much mass the star had is what happens next.\n\nIn the case of the largest and most massive of stars the result is very dramatic. Without fusionable elements, the gravity crushes the mass of the star down to a size so small that the velocity required to overcome the gravitational pull and escape the surface of the star is greater then the speed of light. Nothing can move faster then light, thus nothing can escape this star.\n\nThis is what a black hole is. You know how the shuttle has to be moving about 11 kilometers a second to escape Earth's pull? If the Earth was a Black Hole, the shuttle would have to be moving faster then the speed of light to escape. This is impossible.\n\nAs for whether or not they exist, it's true that they are hard to spot. However if you watch the matter surronding a black hole there are signs. In Cygnus X-1, there is an object "eating" a blue giant star that may just be a black hole. In fact, astrophysicists have hypothesized that any single star that has more mass then about 45 Suns will eventually become a Black Hole. The theory is that if these stars are left alone, becoming a Black Hole is inevitable.\n\nAs for what happens to light, we know that light goes in, it doesn't come out, and as it gets close it shifts toward red. That's about it.
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A star is a big mass of gas. It originated as a hydrogen cloud  that started contracting because gravity pulled it together. When this happens the interior gets denser and hotter. Dense enough and hot enough for fusion reactions to start. The latter produce heat and light that pushes outwards.\n\nThe result is an equilibrium between gravity and the light radiation. The star stabilizes and stays stable for billions of years. The sun is in this stage.\n\nHowever, when the hydrogen is burnt up, the outward pressure is taken away and gravity takes over again. If the mass of this burnt out star is big enough, then there is nothing to counteract gravity.\n\nThe mass of the star will be more and more concentrated in a smaller and small volume. Gravity at the surface will become so strong that not even light can escape from it. \n\nThat is a black hole.
378154
It is not a star going supernova that creates a blackhole. Its the collapsing of its core that does. Just wanted to clear that up.\n\nA blackhole is created when a star is so massive (at least 20 times that of our Sun) that the bonds between the atoms, or molecules, are no longer strong enough to fight against the force of gravity.  This causes the star to collapse in on itself, and eventualy create a blackhole.\n\nThere are some beliefs that a blackhole could lead to a parallel universe.  But this gets a bit hazy in details, as no one knows for sure, and its currently impossible to prove or disprove.  A blackhole has an "event horizon", that once you have passed through you cannot get back out, nor can you see past it from the outside.  Because of this event horizon, it is very unlikely that you could get out of the blackhole into another universe .....\n\nHowever ..... A theoretical astronomical body called a white hole has been predicted, although its existence has not yet been proved.  It is the opposite of a blackhole, in that instead of "sucking" up all the matter in its path, it spews it out instead.  IF this exists, then there is a chance that a white-black hole pair could be a gateway to another universe, or another part of our universe.  But I can't stress enough, this is purely theoretical, and absolutely NO proof has been found yet.
13556
There are theoretically two ways in which black holes can form.  Stellar (star) sized black holes have to be above the Chandresekhar limit of 3.2 solar masses, and are formed through the gravitational collapse of stars. They can form whenever conditions are right. These are the types of black holes that astronomers infer from binary X-ray sources and the like.\n\nMicro black holes, on the other hand, can only have been formed in the initial moments of the Big Bang, when intense pressures during cosmic expansion could have collapsed masses smaller than our sun into singularities.  According to Dr. Stephen Hawking's theory of black hole evaporation, all singularities lose mass, through a type of evaporation (the actual mechanism, having to do with vaccum energy and particle/antiparticle pairs is a bit complicated) with smaller black holes evaporating faster than large ones.  By this logic, most micro-holes would have evaporated out of existence in the thirteen billion years the universe has been around, while the larger micro-holes (things with the mass of, say, Neptune) should still be around, though hard to spot.
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no, but i can tell you what we think it is:\n\nit is a star whose gravity is too great for the nuclear fusion in its core to negate.  it collapses in on itself and goes supernova.  then it is a neutron star.  if the gravity is still too great, it collapses some more and becomes a black hole.  its gravity is so strong that light itself cannot escape it (thus it is 'black').  they are suspected to be at the center of many galaxies, especially quasars and other active galaxies.  one is believed to be at the center of our own galaxy, the milky way.\n\nonce again, no one has really seen one, just the indirect evidence that one exists (strange star orbits, gas being sucked into nothing, strange bursts of some kind of rays (can't remember what kind) coming out of the poles, etc.\n\neverybody is pretty convinced that they exist.  its just kinda hard to prove.\n\nps the idiot down there who said black holes are dead galaxies has no clue what he is talking about. please ignore him.  and its not the size of an atom, its an infinitely small point, the swartzchild point.
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I am not quite sure what your asking.\n\nWhen the star is forming, it starts out as a gigantic cloud of mostly Hydrogen. As the stellar material coalesces, the material begins to heat up and the pressure at the center of what will become the new star increases dramatically.  The material becomes denser and is pulled together by its own gravity, heating up as the pressure rises.  Gravity is working to pull the star together, and eventually the ball of gas becomes so massive, that the pressure and heat at its core are sufficient to undergo nuclear fusion.  In order to counteract the force of gravity, the Hydrogen at the stars core undergoes fusion, in the process, producing Helium and a lot of energy.  It is this energy produced from nuclear fusion at the stars core that keeps the star from collapsing in on itself.
631703
Black holes aren't holes in the sense that you're thinking of. A black hole is a region of spacetime (it has 3+1 dimensions like everything else) that has an event horizon (a spherical region) that nothing can escape from.\nTaking the rubber sheet analogy (this is 2+1 dimensional, two spatial dimensions, 1 time dimension), suppose there is a spherical mass placed on the stretched sheet. Depending on how massive that mass is, the sheet around the mass will be circularly distorted, creating a potential energy well. You can roll smaller masses by it. If you roll the smaller mass with too little tangent velocity, it will spiral into the larger mass. If you roll it with a great enough tangential velocity, it may change direction, but it will go right through the potential energy well.\nA black hole has a certain region of its potential energy well (the region inside the event horizon) where no velocity you give a particle will be enough to get it back out of the energy well; all particles entering the event horizon will spiral into the singularity at the center. Part of the reason for this is the limit placed on massive particle accelerations of only being able to accelerate up to the speed of light in vacuum. It is interesting to note that outside the event horizon (assuming a non-spinning black hole), gravity behaves classically. Ie., if the Sun were to collapse into a black hole (which it doesn't have the mass to do), the radius of its event horizon would be less than the current radius of the Sun, so the solar system would continue as usual; the gravitational field outside the event horizon is unchanged.\nAlso, a black hole need not be caused by the death of a star. Primordial black holes are hypothesized to be black holes that formed during the chaotic spacetime of the early universe.
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LAYMAN'S THEORY\n\nBlack holes are objects so massive and compact that no physical body or signal—not even light—can escape from their gravitational pull once it has crossed the so-called "event horizon" around the black hole (for a black hole of the mass of our sun the event horizon would have a radius of just 3 km, hence black holes are comparably small objects in astronomical terms). Besides the frequent stellar mass black holes (which are thought to be generated at the death of stars about 10 times or more massive than our sun) there is a second class of black holes, which reside in the centers of almost all galaxies and are a million to billion times as massive as our sun. Such so-called supermassive black holes are thought to be the central engine of "Quasars," the most distant and luminous objects known in the universe. Their electromagnetic emission is thought to arise when gas heats up to temperatures of million of degrees before falling beyond the event horizon of a supermassive black hole. In order to find evidence for the existence of such objects, one has to show that so much matter is concentrated in such a small volume that all alternatives to black hole can be excluded—e.g., dense clusters of dark astrophysical bodies such as planets, neutron stars, etc. This is a difficult task in extragalactic systems because of their incredibly large distance. The center of our home galaxy, the Milky Way, however, is about 100 times closer than our next major neighbour galaxy, the Andromeda galaxy. Therefore the undertaking of finding strong direct evidence for the existence of supermassive black holes is most easily done in the Milky Way. For probing the gravitational field at the center of the Milky Way one can use stars as test particles. Imagine the following scenario: If our sun did not give off any light, we would still know of its existence because the gravitational pull of the Sun (along with the angular momentum of the Earth) makes our home planet move around it once a year. In a similar way we have observed the movements of stars close to the supposed supermassive black hole, called Sagittarius A*, in the center of our Milky Way for over a decade. A star was found that moves around Sagittarius A* once every 15 years. By inferring the properties of its orbit with the help of Kepler's laws it was straightforward to show that the (dark) object that forces the star onto its orbit must have about 3.5 million times as much mass as our sun. Furthermore, this mass must be concentrated into a volume just about three times as large as our solar system. Since there is no other known physical object with these properties that can be stable over a significant length of time (compared to the lifetime of our galaxy of about 10 billion years) we concluded that the Sagittarius A* is indeed a supermassive black hole.
914906
Its a remain of a exploded star. After explosion, under it own gravitational force, it compacts so much that after certain point its escape velocity crosses the speed of light. So even light cannot escape from it. Thats why its called Black Hole.\nCheck out this URL and get to know more of this interesting thing of this Universe.\nhttp://en.wikipedia.org/wiki/Black_hole
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A neutron star is one of the few possible endpoints of stellar evolution. A neutron star is formed from the collapsed remnant of a massive star after a Type II or Type Ib, or Type Ic supernova.\n\nA typical neutron star has a mass between 1.35 to about 2.1 solar masses, with a corresponding radius between 20 and 10 km (they shrink as their mass increases) — 30,000 to 70,000 times smaller than the Sun. Thus, neutron stars have densities of 8×1013 to 2×1015 g/cm³, about the density of an atomic nucleus.[1] Compact stars of less than 1.44 solar masses, the Chandrasekhar limit, are white dwarfs; above three to five solar masses (the Tolman-Oppenheimer-Volkoff limit), gravitational collapse occurs, inevitably producing a black hole.\n\nDue to its small size and high density, a neutron star possesses a very high rotation speed, as one revolution can take anything from one seven-hundredth of a second to thirty seconds and a surface gravity 2×1011 to 3×1012 times stronger than that of Earth. One of the measures for the gravity is the escape velocity, the velocity needed for an object to escape from the gravitational field to infinite distance. For a neutron star, such velocities are typically 150,000 km/s, about 1/2 of the velocity of light. Conversely, an object falling onto the surface of a neutron star would strike the star also at 150,000 km/s. To put this in perspective, if an average human were to encounter a neutron star, he or she would impact with roughly the energy yield of a 100 megaton nuclear explosion (a power equivalent to twice the tsar bomba, the biggest nuclear weapon ever detonated).\n\nA black dwarf is a theoretical astronomical object, constituting the remains of a Sun-sized star which has fused all of its original hydrogen and helium fuel to heavier elements such as carbon, oxygen and nitrogen and subsequently lost its remaining energy due to radiation. In other words, a black dwarf is a white dwarf that has cooled down so that it no longer emits heat or light. None are known to exist in our universe, as the time taken for a white dwarf to cool to such a degree is hypothesized to be longer than the age of the universe.\n\nEven at the time when black dwarfs exist they may be extremely difficult to detect, emitting very little thermal radiation (if any) at a temperature not much above that of the cosmic microwave background radiation. They may be detectable through their gravitational influence.\n\nBlack dwarfs should not be confused with brown dwarfs, which are formed when gas contracts to form a star, but does not possess enough mass to initiate and sustain hydrogen nuclear fusion. "Brown dwarfs" were at times called "black dwarfs" in the 1960s.\n\nBoth black dwarfs and white dwarfs are degenerate dwarfs.\n\nI hope this helps you out in your science class young lady.  Aloha.