# Dark Matter & Black Holes

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#### clpc

##### Guest
I am just an interested person with an idea that is probably totally wrong but I would like to know for a fact whether I am right or wrong.<br />Is it known for a fact that a galaxy that has what is considered to be a black hole at its center spiraling inwards, could it be spiraling outwards?<br />If it's possible that a galaxy is spiraling outwards then the big black (hole or disc) at the center could be the mysterious dark matter that we dont seem to be able to find.<br />This is just a case of looking for a simple answer to a complicated problem.

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#### tfwthom

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Maybe this will help..........<br /><br />Black Holes FAQ<br />by Ted Bunn<br /><br />What is a black hole?<br />--------------------- <br />Loosely speaking, a black hole is a region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull. Since our best theory of gravity at the moment is Einstein's general theory of relativity, we have to delve into some results of this theory to understand black holes in detail, but let's start of slow, by thinking about gravity under fairly simple circumstances. <br />Suppose that you are standing on the surface of a planet. You throw a rock straight up into the air. Assuming you don't throw it too hard, it will rise for a while, but eventually the acceleration due to the planet's gravity will make it start to fall down again. If you threw the rock hard enough, though, you could make it escape the planet's gravity entirely. It would keep on rising forever. The speed with which you need to throw the rock in order that it just barely escapes the planet's gravity is called the "escape velocity." As you would expect, the escape velocity depends on the mass of the planet: if the planet is extremely massive, then its gravity is very strong, and the escape velocity is high. A lighter planet would have a smaller escape velocity. The escape velocity also depends on how far you are from the planet's center: the closer you are, the higher the escape velocity. The Earth's escape velocity is 11.2 kilometers per second (about 25,000 m.p.h.), while the Moon's is only 2.4 kilometers per second (about 5300 m.p.h.). <br /><br />Now imagine an object with such an enormous concentration of mass in such a small radius that its escape velocity was greater than the velocity of light. Then, since nothing can go faster than light, nothing can escape the object's gravitational field. Even a beam of light would be pulled back by gravity and would be unable to escape. <br /><br />The idea of a mass co <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

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#### clpc

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Thanks for that.... it helps a great deal.

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#### toothferry

##### Guest
Are you proposing that instead of a black hole at the center of a galaxy sucking everything in that instead there is a dark matter region spitting new matter out? now that's an interesting hypothesis. <br /><br />just through observation atronomers already see examples of what galaxies looks like thousands of years ago, millions of years ago, and also billions of years ago. But what exactly will a galaxie like the milky way look like millions or even billions of years from now?

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#### venera

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aren't jets emmited from black holes?

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#### alokmohan

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Thaks for the reference.

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#### pistino

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Is it possably for as black hole come and destroy the earth.

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#### tfwthom

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In the news.......<br /><br /><br />Black-hole breakfast <br />New research finds black holes gobble neutron stars in one quick gulp.<br />Robert Adler<br /><br /><br />May 26, 2005<br />What happens when a neutron star edges too close to a black hole? Recent studies applying relativistic instead of Newtonian rules show that, under most circumstances, neutron stars plunge directly into black holes without forming an accretion disk. These new findings will help astronomers trying to understand gamma-ray bursts (GRBs) and listening for gravitational-wave signals from such events.<br /><br />Theorists first tried to analyze the encounter between a neutron star and a black hole using Newtonian physics — far easier to apply than relativity. Their studies suggested the black hole would strip mass from the neutron star while it remained in a stable orbit. This would form an accretion disk, and the transfer of mass would push the star into a higher orbit. Some studies showed neutron stars "bouncing" into eccentric orbits that would generate repeated bursts of gamma rays and gravitational waves. In most cases, GRBs and gravitational waves would appear over an extended period of time.<br /><br />M. Coleman Miller, an astrophysicist at the University of Maryland, has now tracked neutron star-black hole tangos under relativistic rules, with strikingly different results. He built on recent work by theorists Alessandra Buonanno (University of Paris), Stuart Shapiro (University of Illinois at Urbana-Champaign), and Fred Rasio at Northwestern University, among others. The study will appear in The Astrophysical Journal Letters. <br /><br />Miller tells Astronomy that in Einstein's rubbery space-time, rather than forming accretion disks and orbiting black holes for extended periods, neutron stars plunge "promptly" into black holes. <br /><br />How promptly? According to Miller, once a neutron star ventures closer than 3 times the radius of a non-spinning black hole, it will vanish within a millisecon <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

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#### alokmohan

##### Guest
Cming to original title.What is dark matter is not defined.Black hole may be one of them.Brown dwarf,WIMPS ,and so many other candidates.

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#### alokmohan

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But we hould seriously know it.

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##### Guest
I think the invisible force/matter in the center of a gallaxy may just be a preasure zone, or anti gravity.<br /><br />I don't think it contains invisible matter like you think. I know the center of a gallaxy like a hurricane acts different in the middle.<br /><br />I knew black holes existeted since I was born, seems... You just can't tell what a black hole consist of. <br /><br />It grows in its gravity pull untill it gives out. That's when it has a reverse reaction. <br /><br />It has to reverse, cause it will get soo tight it no longer can increase in gravatational pull and implode on itsself.<br /><br />It will still be a larg black whole again someday. This is how our Universe lives and keeps changing. <br /><br /> Exploding and reloading...

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#### emperor_of_localgroup

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SpaceInvador, sorry to say, I most often read your incoherent posts and laugh or smile. But once in a while I do see some 'meat' in your posts.<br /><br />What you just said about 'end of a black hole' was what I have been holding in my mind for sometime now. A practical object does not turn into sigularity, only an imaginery object can. This is what we expect in our everyday life as long as the real object is part of THIS universe. That is why I accept any theory beyond event horizon with a question mark in my head. Sooner or later, for this reason or that reason that we still dont know, a black hole, if any, must explode or implode before it reaches singularity. That is a scene from a more realistic world. <div class="Discussion_UserSignature"> <font size="2" color="#ff0000"><strong>Earth is Boring</strong></font> </div>

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##### Guest
Why do all who have the greatest of minds get laught at? I know I jump around a little or alot in my description of things and my spelling is horrible. <br /><br />I'm trying to learn how to think outloud/in writing without confusing you and myself.<br /><br />And, don't be sorry I screw-up or don't know what the heck I'm talking about. I think we all have something to learn, even from me.

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#### sporda

##### Guest
This may be far fetched but how hard would it be to artificially create a sun/star the size of a baseball or bigger and if it were destroyed would it supernova like a nuclear bomb, end in a black hole, or become somthing else like a neutron star, quasar, pulsar, or something else?

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#### lunatio_gordin

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Not as much disagreement as you'd like to believe.

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#### lunatio_gordin

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Well, There *was* a problem with that a while ago, I remember reading about it. BUt i think it's been straightened out, for the most part. I'll check my books and get back with it. <br />EDIT:<br />I can't seem to find my book. disappointing...<br />Anyway, i did find this:<br />There was never too much problem with the idea of the age of the universe vs. the age of the solar system. The scenario as I have always understood it is this:<br /><br /> * Stars form fairly rapidly, in only a few million years.<br /> * Big stars, those which eventually explode, are short-lived. <br /><br />So picture this: a few million years to form a big star from a cloud of primordial hydrogen and helium; then a lifetime of not more than a few million years, followed by a violent explosion which synthesizes all the elements up through who-knows-what -- at least to uranium, probably further. Finally, another few million years to reform and condense into our solar system, which has an age of some 4.5 billion years.<br />http://www.madsci.org/posts/archives/feb98/887762110.As.r.html

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