we all know that a black hole is a body so heavy that nothing cannot escape it's boundaries, not even light, because the escape velocity from a black hole is larger than C, but we also know that stars are only able to light up and produce fusion if they are massive enough and the pressure is strong enough for atoms to fuse. as far as I know there is no rule for a maximum pressure, beyond wich the atoms would not fuse. and when a massive star colapses it either becomes a neutron star or a black hole, and in my opinion the only difference between a neutron star and a black hole is the weaker gravity from a neutron star. what are your thoughts on this, is a black hole still fusioning atoms and producing light? just because the light will never escape the event horizon doesn't mean it isn't producing light.
http://www.astronomy.ohio-state.edu/~ryden/ast162_5/notes21.html Presumably, since black holes are "denser" and "smaller" they will emit at higher temperatures than neutron stars - hence further into the x-ray and higher wavelengths -no light. (Probably).
A lot of black holes are surrounded by remnants of their parent star. That material could absorb X-rays and re-emit visible light.
A lot of black holes? How many do we actually know exist? What radius is this material? Since nothing can escape from a black hole how do the x-rays exit?
Try to puzzle out why the black hole at the core of the Sombrero galaxy is a huge emitter of radiation and the one at the center of our galaxy seems to be a blank. I think ours hasn't been fed lately. The Sombrero galaxy looks like it constantly irradiates its daughter planets at a very high intensity. It also has a planetary nebula type of debris ring around the glowing area which makes it look like it's a supernova remnant instead of a galaxy. Something big got sucked in there and got destroyed. I mean, horribly big. Simply this: Even accepting the idea that a black hole prevents all radiation from escaping, there are a few loopholes. One is that there can be enough mass in the accretion disk under enough heat and pressure to radiate heavily. Another is that stellar size black holes are Kerr-Newman type, not a point source at all, so they can have zones right in the middle that radiation and matter can escape from. Also, Oli, you're the one that said that black holes would emit at higher frequencies than we can see. Those higher frequencies energize matter by simply heating and ionizing it, and that can create a glow at lower frequencies.
No I didn't, read the OP, we were discussing what radiation would be produced that WOULDN'T escape the event horizon.
Since most of the galaxies that we have observed have black holes and they are in a state of flux from active to inactive, we are just starting to learn the truth about them. Astronomers theorize that black holes are the single most thing that could have actually started a galaxy to begin with and they can spew out stuff as well as digest it which is something new that has been found recently. Only time will tell us more about these black holes so let us wait and see what they uncover.
Yeah? Depends on what evidence you are prepared to accept as being a black hole. Could be as low as 14 known, 1 per galaxy is extravagant. WTF is an "inactive" black hole?
Well, outside the event horizon can be huge amounts of matter that are under extreme stress. By current theory black holes can emit radiation from outside the event horizon this way.
Using doppler measurements, many galaxies MUST have a black hole at their center to account for the rate at which the stars in the core move. These black holes have been found in every type of galaxy. Some have been known to have 2. And these are just the cores, there are probably many more in each galaxy in general. 1 per galaxy is WAY underestimating. A black hole not currently consuming matter.
'kay, the NASA site needs updating: That was all I found. Please Register or Log in to view the hidden image! Again, thanks. I thought they'd gone and added another property while I wasn't looking. Please Register or Log in to view the hidden image!
A black hole is a singularity, yes? So doesn't it basically have infinite gravity, which would collapse anything into a singularity, which would prevent fusion? Would it basically destroy the protons? They wouldn't be torn apart into their constituant quarks, they'd basically become so massive that they punched holes in spacetime and -- weird shit would happen. Good question!
Oli, your link is about x-ray binary black holes, stellar-mass black holes with a companion. He is simply stating there are 17 known binary systems with a less than three solar-mass companion (stars or neutron stars) and three with companions of greater than 3 solar masses, most likely both members being black holes. ALL spiral type galaxies are thought to contain central supermassive black holes, and they are being found in other type galaxies as well. As star_kindler posted, some galaxies contain more than one supermassive black hole (most likely from merging galaxies) and many, many stellar-mass black holes.
Xev, Schwarzschild mathematics predict a non-rotating black hole with a singularity at the center where the math breaks down. That type would have to be formed from a non-rotating star (none known) when it collapsed, or have lost its rotation over a great period of time due to gravitational energy losses. The Kerr black hole is a rotating black hole, the type thought to actually exist in the universe. The Kerr black hole does not contain a point-like singularity as in Schwarschild black holes, but possibly a ring-shaped singularity. There is much debate as to the exact properties of the rotating black holes. Many studies are currently focused on them and some observations do not seem to correspond with older theories. For example, some black holes are observed to emit massive amounts of energy in the form of 'jets' from their poles.
2-inquisitive: Okay, but that's not necessarily what I was asking. The electrons would have been forced away by the pressure of the collapsing star, proton-neutron fusion would probably then occur and form deuterium nuclei, but what would happen as the pressure continued to increase? Wouldn't those nuclei have mass approaching infinity once beyond the event horizen?
Xev, Yes, I don't know an exact answer to your question. That was the reason I didn't quote the question itself, but the specific black hole model you were presumably using, the Schwarzschild model of a non-rotating black hole. This is the point I was trying to address in my previous post. In the non-rotating Schwarzschild model, particles fall straight to the core, forming the singularity you speak about. It is an idealized model that relies on perfect symmetry during the collapse to form the point singularity. In the rotating Kerr black hole, particles don't fall straight to a central point (singularity), but orbit (revolve around) the core at greater and greater speeds as the star collapses. The 'singularity' formed would probably be in the form of a thin ring just inside the event horizon, rotating at near light speed. I don't know if a proton and a neutron could be pressed together to occupy the same space (I gather that is what you mean by fused), but I remember the Pauli exclusion principle prohibits two neutrons in the same state from occupying the same space. I think the Pauli exclusion principle applies to all fermions, but someone more knowledgeable in QM would have to answer. In short, I believe the Schwarzschild model of a non-rotating black hole is not physical, as it ignores too many variables such as rotation, and relies on a perfect symmetrical collapse to form the point-like singularity. Of course, that statement is just my personal opinion, but I think most physicists well-versed in black hole mechanics and observation feel the same. I think you meant to say the density of a point singularity would approach infinity. The mass of a star does not change due to collapse into a black hole, except for losing mass from the outer layers that are ejected during the collapse. For example, if it were possible (its not) for the total mass of our sun to collapse into a black hole, the Earth's orbit would not be altered. The Earth would not feel an increased gravitational pull, or be affected in any way except for lack of radiation from the nuclear fusion happening in our sun. There is one further point I would like to make. Many seem to think of a black hole as something like a giant vacuum cleaner, sucking in everything within its grasp. That is not true, and in fact there can be stable orbits within the black hole's accretion disk, just as there are stable orbits around our sun. That is generally the way supermassive black holes are located, by observing its effects on the stars that are orbiting it. There is a feature of black holes known as the minimum radius of the last stable orbit that is very near the event horizon. Any particle that moves inside this radius must eventually fall onto the event horizon and disappear from the view of an outside observer. The particle will be moving at very near the speed of light in this last stable orbit.
