Q & A: Black Holes

		def.: A dense, compact object whose gravitational pull is so strong that - within a certain distance of it - nothing can escape, not even light. Black holes are thought to result from the collapse of certain very massive stars at the ends of their evolution. Field Guide to Black Holes Chandra Images: Black Holes

Black holes, Light, Matter and Time

Q: What it looks like when black holes are made, how long it takes to make them, and how do they mess with the stream of time?

Q: If two objects were drifting towards a black hole at the same speed and distance from the black hole, if they had different masses would the heavier one get "pulled" in first?

Q: What if we, and everything that we have seen are inside of a very massive black hole and outside of it is a very unknown universe?

Q: How far are black holes from one another?

Q: I have always wondered if a black hole can move through space? And, if they trap everything around them how can we be sure they don't move, if we can't see it?

Q: Is it possible for a black hole to "eat" an entire galaxy?

Q: Can the recent discovery about black holes "recycling" fuel help us here on Earth?

Q: If light cannot escape black holes, how can we take pictures of them?

Q: Is there a large difference in the composition, density, or distribution between seyfert and spiral galaxies, assuming equal mass?

Q: Is our solar system in a black hole?

Q: Should it be concluded that black holes reach unimaginable limits of expansion?

Q: Is it possible that a system of two black holes could exist in orbit, such that at a point during their orbits their event horizons cross, causing an area of space to be within both event horizons? If so, what would happen to objects in this area?

Q: When a star and a black hole encounter one another, some of the matter in the star may enter the black hole while a lot of the star's matter may be spun off out into space. What becomes of the contents of two black holes that collide? Is some of the material returned to normal space and time?

Q: Could you explain the last announcement from Stephen Hawking about black holes?

Q: What are "ergosphere" and "stationary limit", and what is an "event horizon"?

Q: What does the exclusion principle state? When a star collapses into a black hole, why does the exclusion principle not apply?

Q: I would like to know if Sagittarius A* is exactly in the center of the Milky Way. If not, then where is it? I heard that it is not in the center because it balances the galaxy's density. Is this correct?

Q: If a black hole could 'eat' so many stars but still conserve their energy, how is it that the material the black hole is made from could withstand such an enormous energy?

Q: Could you please tell me which is more common in our Galaxy: white dwarfs or black holes? Why?

Q: I would like to know how black holes evaporate. What is meant by "Hawking Radiation"? Who proposed this theory that black holes evaporate and how? Also, after evaporating, where do black holes go or what do they form?

Q: I would like to know what exactly is in a black hole. Does anyone know? Is there a way to get a satellite near one to bring back images from inside the hole? What makes the black hole so devastating? The idea of them has always seemed so frightening.

Q: I found the information on the center of our galaxy most intriguing, however, none of it tells me what the "lifecycle" of this phenomenon at the center of our galaxy is, and how it affects the rest of the galaxy. Can you tell me more about that?

Q: If, within a given radius {proportional to mass}, nothing escapes the attraction of the Black Hole, won't the Hole continue to attain mass,growing ever larger? And if this is so, the 'event horizon' will also grow ever larger, consuming more and more of anything passing by or 'consumed' by the ever-expanding gravitational field? If so, then, eventually, why wouldn't the entire universe be 'consumed' by the presence of the millions of ever-expanding Black Holes?

Q: If nothing can escape from a black hole, then won't the whole universe eventually be swallowed up?

Q: Does the event horizon in a black hole face only 1 or all directions? In a three dimensional universe, a black hole would seem to form in a slightly round form. It seems hard to imagine a 3-d tear in space and time.

Q: If X-rays are produced by a high-speed collision between an electron and a proton and X-rays are observed to emanate from the cores of galaxies (among other places) why can't we speculate upon a proton star in the center? Why does theory predict that a black hole is accelerating matter that emits X-rays instead of a Protonic star whose electromagnetic strength is attracting electrons that in turn emit the X-rays?

Q: I am interested in determining if the overall total black hole mass content of elliptical galaxies is usually less than that of typical spiral galaxies. Detection of stellar mass black holes in distant elliptical's is currently very difficult...Nevertheless, your Chandra team has revealed X-ray evidence for some black holes in binaries, particularly in globular clusters, of certain elliptical's like NGC 4697. Does this suggest that there is essentially no difference between spirals and elliptical's in their ability to create stellar mass black holes?

Q: What do the team at Chandra think of the alternative argument for "Black Hole" type phenomena such as "Gravistars"?

Q: Is it possible that a black hole could become so isolated that it becomes essentially invisible?

Q: The temperature of a black hole is only a fraction of a degree above absolute zero. How is this possible when the black hole ingests everything within its grasp ?

Q: How is it possible to measure the density of a black hole, let alone a supermassive black hole.

Q: Can you tell me what the 15 or so points of light are that show on the NGC 720 photo on the left and why they are not on the photo on the right?

Q: How fast do gravitational waves travel?

Q: I always wanted to know that when two black holes same gravitational pull perfectly identical in physical, numbers, energy and everything, are facing each other what would happen?

Q: Why is time influenced by gravity?

Q: Black hole gravity is strong enough to trap light. So exactly how hard would the gravity pull on you and a spaceship near the core?

Q: I have always been told that black holes cannot be seen. Could you please explain this to me?

Q: When a black hole sucks a star-in-main-sequence what happens to it once inside?

Q: Do black holes have the ability to devour stars whole, instead of pulling matter off of them bit by bit?

Q: Are there any known emissions of any kind (X-ray or otherwise) from black holes?

Q: Since time slows down in a gravitational field, how would anything ever cross the event horizon in the life of the universe?

Q: I read in a book that an average adult astronaut would die if he/she was sucked into a black hole miles before the person was even near the black hole. Is that because the amount of gravity being sucked in by the black hole is crushing the person?

Q: The way that I understand it, the reason a black hole looks "black" is because its gravity is so great, that light cannot escape it. In order for light to become "trapped", does its speed have to change?

Q: How can black holes that are as massive as you describe be positive influences in the cosmos?

Q: During stellar gravitational collapse, what could be the impact generated by the variation of gravitational forces on the space fabric?

Q: Is the light of the black hole "images" from your web site X-ray light from inside the black hole?

Q: What kind of radiation is used to gather information on black holes, and how?

Q: "The gravity of a black holes falls off inversely as the square of the distance?" Sorry what does that mean exactly?

Q: How can an X-ray telescope observe X-rays from a black hole? I thought nothing could escape from a black hole.



Accretion Disks and Jets from Black Holes

Q: Could you explain why a black hole without an accretion disk can not have a magnetic field? Is it possible that the mass within a black hole could generate a magnetic field, but the field lines have been drawn in beneath the event horizon by the intense gravity?

Q: A magnetic field is produced by a circulating charge, so if the net charge is zero a black hole should not have any magnetic field, so how could a a black hole have a magnetic field to produce the jets seen rushing away from them?

Q: How do the jets from a black hole interact with the surrounding space?

Q: How can gas fall into a black hole and also blown away from it at high speed?

Q: Could Chandra see magnetic pulses coming from black holes?

Q: What is ADAF (Advection Dominated Accretion Flows)?

Q: Could the rotation of XTE J1550-564 around the galaxy affect its jets in any way?



Origin and Evolution of Black Holes

Q: My question is what happens when two black holes with the same mass, size and everything encounter each other? Question two, what is a quasar?

Q: What would be the driving force behind the creation of Black Holes?

Q: How long does it take a star to form a black hole after its death?

Q: What are black holes made of?

Q: What ultimately happens to black holes?

Q: I have read that the universe, at its inception, may have included billions of black holes that don't appear to exist currently. If that is the case, have some or all of these black holes ceased to exist at some point?

Q: Are there truly 100's of billions of suns locked up in just one black hole?

Q: Do all black holes have to be massive objects? Do all black holes have to be dense?

Q: I have read your Q & A on what happens to a star when it goes into a black hole, but where does the star go to? Surely it can't just disappear, could a black hole be something like a star gate or worm hole?

Q: How does a black hole consume matter? What happens to the matter it consumes?

Q: Do Black Holes ever run out of energy? If so, what happens to the Black Hole when the energy runs out?

Q: Were galaxies born out of the supermassive black holes at the edge of the galaxy?

Q: Could a black hole fill up? What would take place? A small Big Bang, or would it just disappear?

Q: What is the life cycle of a black hole? Do they implode? Explode? What happens to them at the end of the "big Bang"?

Q: If matter was so dense at the time of the Big Bang, how come it didn't form a black hole?

Q: Could a black hole in our galaxy ever be strong enough to suck our solar system into it?



Specific Source

Q: How long would it take for scientists to notice the effects of the NGC6240 merger in our galaxy and/or in other galaxies?

Q: I was hoping you could tell me the date scientists confirmed the presence of the black hole in the center of the Milky Way?

Q: What is the meaning of the "*" in Sagittarius A*?

Q: In the Chandra image of XTEJ1118+480, are we observing the center spectral diagonal line as a line or are we seeing the line as the outside edge of a flat plane?

Q: Can you tell me what is the distance between the XTEJ1118+480 black hole and its companion star?

Q: In regard to the recent black hole flare, something occured to me. If light cannot escape the black hole, what happens to it? Is it bright somewhere within? Or are the photons destroyed or changed?

Q: Does Chandra indicate more Quasar/Super Massive Black Holes like PKS 0637-72 than previously were thought to exist in the early years of the universe? Studies I have read theorize the universe will fizzle out after a "Black Hole" era.

Q: Who is involved with the analysis of the black hole at the center of our galaxy? Who will be in charge of naming this object?

Q: In your story of Mid-sized black holes the comment was made, "The black hole found in M82 packs the mass of at least 500 suns into a region about the size of the Moon." How is this possible?

Q: I have read that the Chandra X-Ray Observatory has detected a powerful black hole in our galaxy and that it is pulling Earth, the Sun and our entire solar sytem toward it at more than a million miles per hour. Is this true?

Q: When was the fact that there is a black hole at the center of our galaxy established as a fact?



Miscellaneous

Q: Could some catastrophic event such as a black hole tearing a star apart or the universe exploding be headed our way - without our knowledge?

Q: Does our galaxy contain a black hole and, if so, what do scientists know about it? Why does this phenomenon exist?

Q: How do black holes affect our solar system?

Q: Will the collision of the two supermassive black holes REALLY damage the entire universe? Will it affect Earth?

Q: Who proposed black holes exist?

Q: Could the supermassive black holes discovered at the center of nearly all visible galaxies possibly make up for the lack of mass observed in the universe? And since so little is know about the interior regions of a black hole, where the majority of physics and mathematics may not even be applicable, could the computations of the mass of these large bodies be miscalculated?

Q: If it is true that the magnetic field of a black hole is so strong that even light can't escape it, what will happen when one black hole comes under the influence of the magnetic field of another black hole?

Q: Are worm holes traversable?

Q: I have a theory that black holes produce a spout of energy at the north magnetic pole... Could I be correct?

Q: Could it be that a black hole is really a place where things get "sucked in", reduced to thier most basic components, and "spit out" across the universe?

Q: Are there any good books on black holes that are not too technical?