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Space

Universe Teeming With Black Holes 102

Posted by timothy
from the so-is-my-heart-dammit dept.
Porfiry writes "For the first time, astronomers believe they have proof black holes of all sizes once ruled the universe. NASA's Chandra X-ray Observatory provided the deepest X-ray images ever recorded (a million-second exposure), and those pictures deliver a novel look at the past 12 billion years of black holes. Combining infrared and X-ray observations, the Penn State team found veils of dust and gas are common around young black holes. 'The discovery of this object, some 12 billion light years away, is key to understanding how dense clouds of gas form galaxies, with massive black holes at their centers,' said Colin Norman of Johns Hopkins University."
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Universe Teeming With Black Holes

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  • But not really surprising. I mean how old is the universe (not just cluster of local space that we've been able to see)? Why's it so surprising that there's tons of black holes out there?


    Chas - The one, the only.
    THANK GOD!!!
  • they have proof black holes of all sizes once ruled the universe

    Why do they always have to bring Microsoft into everything?
  • Time disappears into Linux with nothing to show for it's loss. Coincidence?
  • Ask Art about this on the "Wild Card" line
  • Seriously. How can a black hole disappear?

    If they once ruled the universe, how did they cease and desist?

    Black holes suck up matter/energy.

  • by Niggle (68950) on Tuesday March 13, 2001 @11:05PM (#364916) Homepage
    Black holes "evaporate" via a process known a Hawking radiation. Basically, it works as follows:
    1) A particle/anti-particle pair forms just above the event horizon.
    2) One of the particle gets sucked in, the other escapes.
    The energy to form the particle pair comes from the black hole itself, so that escaping particle carries off some energy. And E=mc^2 so it's exactly the same as if it had carried off some mass from the black hole.
  • You mean that incredible sucking sound has been coming from Redmond all this time?
  • They don't. Chances are they'll want this technology though, ruling the universe must sound interesting to them =] BTW: "The Chandra data show us that giant black holes were much more active in the past than at present,"
    In what way is a black hole active? does it play Zero Wing??
  • by IvyMike (178408) on Tuesday March 13, 2001 @11:06PM (#364919)

    Why's it so surprising that there's tons of black holes out there?

    I agree: it doesn't seem very surprising. But this leads us to the opposite question: Why's there so much non-black hole stuff out there? According to the article, black holes were much more active in the past. Why did the situation change?

  • If I wanted a limp biscuit's opinion, I'd badger the Pillsbury Doughboy.
  • Wouldn't it be nasa.gov?
    (nice try)
  • http://artbell.com/nasaufos.html
  • To mention badgering the Pillsbury Doughboy in a thread about black holes is ... um ... kinda kinky, IMHO. But hey, if that's your thing, I got no problems with it.
  • Still. You would need to have a bigger evaporation rate than sucking-in-matter-into-the-hole rate. But this might happen AFTER the entire galaxy is consumed? Or am I not thinking straight?
  • So presumably this was a lot of smaller exposures that were summed to total the 15.5 days that would normally take?

    I can't hold a camera steady for that long, what with all the crazy spinning going on and all...

    Oh, and the earth moving, too.

    Seriously, does anyone know how exactly that works? The article just says

    The images, known as the Chandra Deep Fields, were obtained during many long exposures over the course of more than a year[...]The group's 500,000-second exposure included the Hubble Deep Field North, allowing scientists the opportunity to combine the power of Chandra and the Hubble Space Telescope, two of NASA's Great Observatories. The Penn State team recently acquired an additional 500,000 seconds of data, creating another one-million-second Chandra Deep Field, located in the constellation of Ursa Major.

    -j

  • If they think this is enough to account for all that "Dark Matter" we always hear about?

    I think one of the more interesting things I've learned of late about black holes is they don't last for ever. Even something so powerful that nothing was thought to escape it will lose mass and eventually die, a strange fitting testament to a universe that we realize increasingly did indeed have a beginning, and will indeed have an end.
  • I think it's because in the past the universe had more matter for the black holes to consume. But eventually once they had consumed all the matter around themselves they became dormant/inactive and thus fairly hard to see.
  • Light is like RF.

    it can be absorbed. (A roof will block light)
    it can bounce. (a mirror will reflect it)
    it can travel forever.

    RF can be absorbed (your brain and that cell phone)
    It can bounce. (CB'ers know about skip)
    it'l skip when the wavelength hits a FLAT object larger than it's own wave length at 30MHz its like a giant 20' basketball
    It can travel forever in a straight line.

  • by Anonymous Coward
    light doesn't travel for ever does it.

    Yes it does... in a straight line anyhow. A little something called the Laws of PHYSICS. Do you think the beam of light changes its mind after 5 miles or something?

    otherwise those stars in the sky at night would make it day light all the time 24 hours a day.

    The light from distant stars is disappated by 1) gravity of astronomical bodies and 2) the atmosphere. You do realise that distant lightsources would appear DIM, don't you?

    also, do you have any evidence that the universe stops at some point, maybe a photo where the universe stops and beyond it is just, err, nothing? what is beyond it, maybe you could tell me that too.

    What's 'beyond' the universe is irrelevant and has no meaning, due to the definition of what a universe is. How could you possibly measure anything when you have no frame of reference? 'Beyond the universe' = no frame of reference.
  • It's funny, every time I read an article on black holes I read something like this:

    "These data will help scientists better understand star formation and how stellar-sized black holes evolve."

    So, how close are they to to understanding these big black thinggies in the sky? Every time they get a pretty picture of the night sky that is bigger & better they say the same thing, how I see it. Anyone else feel the same way?
  • Chandra is a spacecraft so I suppose its quite easy to keep it still.
  • Considering the average particle density of the universe (IIRC, it's something on the order of 1 proton/km^3), the amount of mass taken away by Hawking radiation when compared to the intake of a small black hole is not insignificant.
  • by Alpha State (89105) on Tuesday March 13, 2001 @11:36PM (#364934) Homepage

    How do black holes form? Normally when matter coalesces it rotates, forming a galaxy , cloud, solar system, etc. I believe the accepted theory on formation of black holes is that a massive star supernovas, exerting huge compression on it own core and collapsing the matter into a black hole which then consumes the rest of the star.

    As there were presumably no old stars to supernova at the beginning of the universe, how did these form? Possibly they are remnants from the big bang or perhaps there were huge amounts of matter which collapsed quickly shortly after the big bang, although these should also leave microwave imprints.

    It's also worth noting that black holes could solve the convex/concave universe problem. It's been postulated that there is "dark matter" we cannot see accounting for the rest of the mass of the universe. If there are lots of small black holes out there it could explain this. This could prove that the universe will eventually collapse back in on itself creating a new big bang, instead of expanding forever.

    Now, can anyone tell me whether this is definitive proof of the existence of black holes, or could these signals be produced by any type of dense matter?

  • and you can see the Andromeda Ascendant.

    I had to say it.

  • Okay, so we're teaming with stars, the universe is teaming with black holes. My bet is that the universe goes for pulsars next; if so, planets will be our next choice.

    When it comes down to nebulae, we'll probably do the usual "I don't care if it's my turn, you can have him." "I don't want him!" thing. Nobody likes the fat kid. We'll get stuck with them anyway; it's not so bad, they're not entirely useless.

    The universe will probably win though. It's a lot older than us.
    ---
  • I still dont get how black holes can crunch matter and enrgy into infinite nothing ? it's just a weak idea , i mean i know it's not suposed to make much sense , but i would rather buy other older theorys like , all the stuff comes out in a somewhere else sooner or latter , like a space fold, or into another dimension, i just dont want to believe the crunch to infinite nothingness, i t seems like a lame way of getting out of explaning where all the " stuff " go's. last dumb thought on my side if there is infinite nothingness, inside a black hole way past the event horizon is there infinite " everything " ? all at once ?
  • how do we actually know if this is the truth , the history of science is riddeld with , breaking theorys that months or years later are dispoved by smarter or more astute people, i am not saying this is the case here , and maybe i have watched to much tv, look at hawkings in the early 90's a few years later he discredited his findings himself ( i saw that on discovery channel, again to much tv, but then again anything i learnt of any worth in life came from tv and movies ).
  • Actualy when they get too much energy, due to the laws of conservation of matter and energy, they finaly explode forming a new galaxie. Most of the black holes are from the original big bang and are part of the expanding universe. They are busy re-collecting small amounts of matter and energy. I don't expect any to explode soon as most of the material needed from the original explosion is still scattered far and wide.
  • What if black holes are the " rivits " of the fabric of the universe, or anchors ther emust be more to it , because if the universe was teeming with them , and lets say that in the beggining teeming phase the universe was a great deal smaller , there fore more black holes in less space , each exerting a vast amount of gravity , would they attract or repel each other like magnets ? and if they repled , would it enhacne the push from the big bang , or act as anchor weights to slow down the furious fast explosion, maybe they were used in the beggining to make sure the intial " bang " never totaly ripped itself up , kind of held it in cheque ? Damit i know what this means , no sleep for me for a week again !
  • On a contrary, it's pretty damn hard. But it's still easier than keeping Earth off spinning..

    Psi
  • If the universe were infinite, we would only see a bright white sky at night ...

    There are entire books devoted to the subject of why this statement isn't true.

    Thanks for playing.

  • I know. I always see something along the lines of...

    This data will help [fill in the type of scientist] understand [fill in the subject].

    Yet, at the same time I'm always hearing about how much they don't know, and how they're not so sure about such and such.

    In this case... how can the universe be teeming with black-holes if some people aren't even sure black holes exist [rediff.com]?

    I think a lot of them say this kind of crap because it makes it seem like all that money spent on research isn't wasted.

    I personally don't feel that it is wasted, mind you. I just wish that every time they made some kind of "cool announcement" it had something more substantial than "we think we may have found something that will lead us to future understanding of a theory we might come up with based on recent findings."

    "Everything you know is wrong. (And stupid.)"
  • by Niggle (68950)
    Yes, the intake rate will exceed the loss by Hawking radiation in a lot of cases. There are a couple of cases where this won't happen:

    1) If there isn't much matter around. Say, after it's eaten everything nearby or if it drifts into inter-galactic space.

    2) It's a small black hole. These won't eat as fast, and energy densities are larger around smaller black holes. This leads to higher rates of particle/anti-particle generation and increased Hawking radiation. Small black holes should evaporate much faster than large ones.
  • Um, excuse me? Dormant? We're talking about a gravitational singularity. It's not like it times out after not collecting any matter for a century or two.

    Now yes, after a large amount of time of no matter coming into the event horizon of a black hole, the accretion disk will 'erode' (for lack of a better term) because no new matter is replenishing it.

    Even when that happens, though, the black hole still will emit x-rays and such, so it is still detectable.

    Kierthos
  • Probably not. Isn't Dark Matter supposed to account for something along 90+% of the 'missing' mass of the universe?

    Although, how did they get that figure (or whatever the real figure is) at all? It's not like we can point to a spot in the sky and say the universe ends there. So how do they (they being the astronomers and astrophysicists) know how much mass is missing? (Sounds like I really need to pick up that book by Hawking...)

    Kierthos
  • by rde (17364) on Wednesday March 14, 2001 @01:19AM (#364947)
    Even when that happens, though, the black hole still will emit x-rays and such, so it is still detectable.

    If the black hole is wandering through the universe having eaten its host galaxy, it'd be damn hard to detect. Even if it's emitting Hawking radiation, this would in no way compare to the emissions of, eg, Cygnus X-1. 'Detectable' is the operative word, here; Chandra is looking back twelve billion years; it's not going to detect anything that isn't (wasn't?) truly spectacular. Sissy Hawking radiation would be damn hard to detect in our own galaxy, let alone one that died before the sun formed.
  • Hmm, that seems to clear something up for me. I had always had the impression that it is the escaped particle that accounts for the "evaporation" and my thought was always, "but wouldn't the particles/antiparticles entering balance each other out?" But if it's _energy_, I guess that answers that...

    --

  • by Anonymous Coward

    You've got it right.

    There are a number of problems too, not just holding the telescope still. You also have to worry about 'overexposing your film' so to speak. Most detectors are some sort of CCD these days (like in a digital camera, only better), and if you let them expose too long, you'll saturate the pixel values.

    I'm not too sure about x-ray observations, but typical optical exposures run from 600-1400s, depending upon the sky brightness, wavelength of the exposure, detector, etc. X-ray count rates tend to be very low (literally on the level where you can count photons), so I would assume they would be longer, but still not a megasecond.

  • by paranormalized (278300) on Wednesday March 14, 2001 @01:45AM (#364950)
    Probably not. Isn't Dark Matter supposed to account for something along 90+% of the 'missing' mass of the universe?

    Although, how did they get that figure (or whatever the real figure is) at all? It's not like we can point to a spot in the sky and say the universe ends there. So how do they (they being the astronomers and astrophysicists) know how much mass is missing? (Sounds like I really need to pick up that book by Hawking...)

    Two words: gravitational lensing...

    Ok, imagine for a second that you're looking at a distant galaxy. Since matter bends light, you get an image of it from one angle. Now, suppose you look for galaxies at an angle just slightly different from the first angle. You see a galaxy. Upon inspection, it looks eerily like the first galaxy... in fact, neighboring galaxies seem to have 'clones' like the first galaxy too! What is going on?!?

    What's happening is you're experiencing a 'lensing' effect by some matter that you can't see, allowing you to see one galaxy from many different angles. You plug the numbers into your computer model of the universe, try to figure out how much matter would produce said effect, (by laws of general relativity), and lo and behold, you get this figure for large amounts of invisible matter!

    Now, what I'm interested in is how many galaxies have 'eaten' all their surrounding dust. If there was any dust, the black hole would compress it to unimaginable degrees as it drew said dust in, producing x-rays of incredible magnitude... some of the brightest/most energy-producing objects in the universe are thought to be such super-holes. So, either those billions of black holes have mostly 'evaporated', (see another poster's explanation of the process), or they have sucked up all nearby gasses/dust... this discovery is going to produce some interesting fodder for the cosmologists. (and no, a cosmologist doesn't worry about makeup, guys, and the modeling careers of universes. Well, maybe some of them do, but that's not their job ;)

    -----
    IANASRP- I am not a self-referential phrase
    -----

  • For those of you who don't know, LYGOS is this project designed to detect and measure 'gravity waves'. Last I heard of it, it was scheduled to be starting sometime soon. If the universe has so many black holes, as this evidence suggests, then they ought to be producing lots of gravity waves... so, have they been collecting data yet? How soon before we get 'gravity wave images' of the universe? Any professional astronomers here? Thanks!

    -----
    IANASRP- I am not a self-referential phrase
    -----
  • by noz (253073)
    "...astronomers believe they have proof black holes of all sizes once ruled the universe."

    A brilliant example of the correct use of scientific language to correctly and accurately describe something.

    Send slaps to timothy [monkey.org] (We all love the work you do *s*).
  • This is not how these particular black holes disappeared.

    Think about it, the mass of a proton, say is on the order of 10^-27kg. The mass of a small black hole is on the order of a few solar masses. One solar mass is 10^30kg. This is a difference of 57(!) orders of magnitude. That is, you have 10^57 protons in a 1 solar mass blackhole. Compare this to the fact that the Universe is only 10^17 seconds old.

    Even if the particles are entirely protons (which they are not, most are much smaller), you would have to be losign particles at an incredible rate just to have this thing evaportate on the Hubble time, much less on a fraction of that. Hawking radiation dosen't even come close to that.

  • Do you have a reference for this?

  • So presumably this was a lot of smaller
    exposures that were summed to total the 15.5
    days that would normally take?


    Yes. The press release says it is the sum of 11 exposures.


    As to the length of individual exposures, for optical detectors (CCDs) you are normally limited by the amount of high-energy cosmic rays collected by the detector, which spoil the data. Thus, individual optical images are rarely longer than one hour.


    With X-ray detectors, you can usually seperate low-energy X-ray photons from high-energy cosmic rays. The limiting factor is the orbit of the spacecraft (if the target ever is behind the earth during the orbit), pointing limitations (the telescope should look at least XYZ degree away from the sun), and radiation in the Van Allen belt around the earth. Uninterrupted exposures of several hours or even days are quite common for x-ray space observatories.

  • rotation can also be fast enough that the equator portion of a collasped object is outside the event horizon and the polar areas inside; resulting in a visable object that would look like core was removed. This object would radiate matter from the equators like any other object.
    Also if a massive object were to orbit a black hole the tidal effect from the second object could distort the event horizon enough for matter to physicaly escape.
    If you take c and devide by Hubble's constant you get 18.6 billion light years, curiously close to the size of the observed universe which is in the 12 billion light year area.
  • By and large they are still there, they have just cleaned out most of the matter in their immediate vicinities, so that they are no longer very easy to detect -- bloack holes are mainly detectable by the energy given off by the matter in the process of falling in, which gets VERY hot.

    Black holes do radiate Hawking radiation, but most big ones radiate less than they absorb from the cosmic microwave background (let alone any remaining infall), so they are mostly still growing. Only when the universe is much, much, much older will they radiate away their mass and evaporate.

    It now seems that most large galaxies have a pretty big (millions of solar masses) central black hole. One theory is that the black hole came first and the galaxy accumulated around it.
  • .. mean that we soon can create our own univserve?
  • by stevelinton (4044) <sal@dcs.st-and.ac.uk> on Wednesday March 14, 2001 @02:15AM (#364959) Homepage
    These black holes may have formed from large clumps of matter relatively soon after the big bang, or from very early, super-large, short-lived stars. They could then have grown by absorbing matter from their vicinities in the relatively dense universe of the time.

    It seems unlikely that black holes make up much of the dark matter in the universe, although they could be a part. We know by looking at the way galaxies rotate and move, that most of the dark matter is in galaxies, but reasonably evenly distributed through them rather than collected at the center. If this was small black holes we'd notice their Hawking radiation. If it was bigger ones, we'd notice their gravity in various ways.

    Finally the X-ray signatures could possibly be other small and very hot objects, but we don't know of anything that could be that small and that hot except matter falling into a black hole.
  • They don't disappear. Black Holes are only detected indirectly, by the radiation of matter falling into them (a significant fraction of that matter can be radiated away rather than ending in the BH, which makes BHs very efficient cosmic power plants).

    As soon as there is no matter left in the surroundings of the BH, it will become 'quiet', i.e. undetectable. When looking at distant galaxies, we look back in time, when the universe was younger, and galaxies with BHs still had much gas and dust in their central regions to feed the BH, resulting in the spectacular energy output of Quasars. Once this supply has ended, the BH would become virtually undetectable, and from a distance, the galaxy would appear just as a 'normal' galaxy like the Milky Way (which is known to have a BH in its centre).

    By the way, BHs can also radiate away via Hawking radiation, but this will take much longer than the current age of the Universe for massive BHs like those in the centres of galaxies.

  • by Random Walk (252043) on Wednesday March 14, 2001 @02:37AM (#364961)
    ESO [eso.org] has also issued a press release [eso.org] on this topic, which IMHO is better than the NASA press release (more facts, less marketspeak).
  • Think about it for a second. Try to imagine the sheer volume of matter (at least the stuff we can see) present in the known universe. Even if truly VAST quantities of it were formed into super-massive stars and, eventually, black holes, there's still a massive amount of matter left over.

    My personal views about a cascading cyclic universe aside.


    Chas - The one, the only.
    THANK GOD!!!

  • by Kibo (256105) <moc.liamg#wan> on Wednesday March 14, 2001 @03:10AM (#364964) Homepage
    Oddly stars that burn out very quickly are the ones that leave black holes.

    A star is basically a diffuse cloud of gas that collapses in on itself due to its own gravity right? Fine. Let's just consider the life cycles of stars then. A typical star, such as our sun, will 'live' about 10 billion years. Right now, and for the past 5 billion or so years it's been burning hydrogen, to make helium. This takes a fair amount of energy and in return releases quite a bit. Helium on the other hand releases much more, but also requires a great deal more pressure. When the hydrogen runs out, the sun will then ignite the helium burning phase and pretty much expand to somthing like the orbit of venus and make the earth look not unlike mercury. In a zone surrounding the helium burning core, hydrogen burning will still continue, but now the burning of helium provides most of the star's energy. And where this hydrogen burning phase lasted billions of years, the accumulated helium will last a few hundred million. But our sun is an unremarkable star. After it is done burning helium it will generate a small nova revealing its white hot core and, in time, a beautiful planitary nebula. Let's consider what might happen if we could add more gas to our sun.

    With more gas, there would be more gravity, so there would be more pressure over a greater volume so hydrogen burning would be more prolific. Hmmmm, by adding more fuel, we're increasing the rate at which it is consumed. So our billions of years of hydrogen burning might be short a billion. So we'll reach the following phase of helium burning sooner, and it too will proceed more quickly. Now we might be able to go beyond helium burning, and burn carbon. In fact this is what the super large stars do. A star of great mass, like a red super giant might be up to 10 billion km in diameter and would not be unlike an onion with different zones of fusion. And this star would be at the end of a life that progressed very quickly. Some lasting only a hundred million years or so, 1/100th the life span of our sun. But what happens at the end of a stars life? It's the energy from the nuclear fusion that literally holds stars up. Without it they collapse. Some stars collapse on an iron core that is so large, that the pressure inside the core forces some electrons into the interiors of all the protons in the iron core of the star. This produces a super nova, but the core, now a vastly smaller ball of neutrons with a 1 km iron crust is what remains. Even neutrons have their limit. They cannot bear an infinite burden. If the core were to be about 2 to 3 times the mass of the sun, it would be so great as to exceed the ability of neutrons to resist gravitation. So a black hole would be born. At least that's the short course.

    Check out Black Holes by Jean-Pierre Luminet from Cambridge University Press ISBN 0521409063.

  • As far as astronomers know, black holes have a bimodal mass distribution, that is, they basically come in two sizes. There are stellar black holes, and supermassive black holes.

    Stellar black holes are formed through total gravitational collapse of very massive stars; stars with more than, say, 30 solar masses. This event is known as a hypernova and produces a gamma-ray burst (GRB), which can easily be seen from billions of light-years away (other GRBs may be produced by mergers of neutron-star pairs, or a neutron star and a black hole). Stellar black holes commonly have masses between roughly 3 and 20 solar masses at formation, but can of course grow by swallowing gas. A well-known example of a stellar BH is Cygnus X-1.

    Supermassive black holes (SMBH) reside in the centers of many galaxies (in all larger galaxies, it is thought) and have masses between, say 100 000 and 10 billion solar masses. The one in the center of the Milky Way is rather smallish for a SMBH with "only" 2.6 million solar masses, and is fairly inactive right now. Active SMBHs are observed as the central "engines" in Seyfert galaxies, Radio galaxies, Quasars and Blazars. The differences between these are primarily due to the angle from which it is observed, and how much gas and dust is around. The larger the SMBH mass, the larger the luminosity it can sustain.

    The ratio between the mass of the central SMBH and the mass of the bulge component of stars in the galaxy has turned out to be astonishingly constant, about 0.5 percent IIRC. This indicates a connection between the formation of the SMBH and the formation of the bulge stars, which happened when the galaxy formed.

    No one really knows for sure how SMBHs form. They are too large and the Universe is too young for them to have been early stellar BHs that simply have grown by swallowing gas. Some think that dense clusters of tens of thousands of stellar BHs and/or neutron stars in the galaxy cores collapsed together and merged in one big crunch. If so, this would be the most energetic events in the Universe, excepting the Big Bang itself. Others think that the SMBHs were formed directly in the Big Bang, and that the galaxies formed around them - that the SMBHs were "gravitational seeds" for galaxies, sort of.

    Actually they seem to have found a few examples of mid-size BHs now, with masses between 100 and 10 000 solar masses, in the cores of globular star clusters. They could conceivably have formed in the same way as SMBHs, only in a smaller scale. And then there might exist tiny BHs formed in the Big Bang, now decaying thru emittance of quantum Hawking radiation, but AFAIK no one has found their very special gamma ray burst signature yet (observed GRBs do not fit).

    As to Dark Matter, most scientists agree on that it cannot be dominated by inactive BHs, because then we would have much more gravitational lensing than we observe.

    /Dervak

  • In accordance with the 'computer scientists not doing anything for other scientists'. One can assume that the astronomers were using computers and related equipment at least for some portion of this "discovery". Meaning that apparently computer scientists ARE helping the scientists and engineers of the world.
  • I would think that the telescope slewing across the sky would not allow for exposures of this length?
  • Actually Chandra is a space-based telescope, very similar to Hubble, but not as famous because it's working perfectly.

    In space, you don't have to worry about the Earth spinning.

    Check out http://chandra.harvard.edu
  • I still dont get how black holes can crunch matter and enrgy into infinite nothing ?
    From my understanding of the operation of a black hole, matter and energy do not become "nothing". They are simply reduced to zero volume. Because we have no direct observation of the behavior of matter under such extreme conditions, we can't say with any certainty exactly where it goes except to a singularity (You can fit a great deal of zero-volume matter/energy into a single point).
  • You should expand on this a little (expand being a strange word to use when talking about black holes). According to Hawking's "A Brief History of Time" black holes do indeed 'evaporate' emitting Hawking radiation as they do so. I leave the details to the reader, mostly 'cos I've only got a BS.c. in physics, and can barely understand the stuff myself.
    -----------------
  • (Infinite space) I always shared that viewpoint, until I was forced out of it by what seems to be the current belief in science:

    Steven Hawkins, a renowned scientist who has written several books on black holes, space, and the like states in "Brief History of Time" space is not infinite. It's a hard to follow book because such a vast amount of concepts are explained (I haven't finished it, yet.) Basically, I'll explain this as layman as possible: The Universe, while not infinite, continues to expand, but it will oneday cease to expand and begin to collapse unto itself when gravity becomes strong enough. An interesting book, but quite trying to read front to back if you haven't taken a lot of science/physics classes/chemistry. As I said before, I always believed space was infinite; I still find it a difficult theory to grasp . . .
  • No, sorry that's a General Products #3 hull.
    -----------------
  • You are looking at images of stellar members, that may have formed (roughly) 7.5 billion years before the formation of the earth. "Far out! man"
  • That is the whole point! Any scientist worth his salt knows damn well that, given long enough, 99.999% of any modern theory will be 'disproved'.

    That is one of the fundamental properties of science itself: the ability and willingness to change. This happens in real life too, you know: think about what you knew at 4 years old. Then what you knew at 13. Then at 25. Then at 40.

    Knowledge is continually updated, and supposed 'facts' are often just an interpretation of reality based on rather miniscule amounts of data.

    Of course, contrast this with the usual nemesis of science: Religion. In religion, you are TOLD what the facts are, and they NEVER change, no matter what new information is learned. Crazy scientists should just do that, according to people like yourself.

  • by Caid Raspa (304283) on Wednesday March 14, 2001 @05:07AM (#364975)
    This is a little bit technical, but you asked for it.

    Chandra has two instruments, ACIS (Advanced Camera for Imaging and Spectroscopy) and HRC (High Resolution Camera). Almost all results going to the general public are made with ACIS. ACIS allows simultanoeus imaging AND spectroscopy. HRC was intended for really high resolution spectroscopy OR imaging.

    ACIS is working nominally, and the Chandra team deserves all the credit for this. However, you do not hear that much about HRC. Why is that?

    This is well documented: Have a look at the Chandra User Manual [harvard.edu]. See section 7.8.2.

    Quote: The anti-coincidence shield of the HRC-S is not working because of a timing error in the electronics. The error is not correctable. As a result the event rate is very high and exceeds the total telemetry rate limit. So, they can not tell particles from X-rays.

    The same in plain english: We are detecting more background than our data transfer can handle. The instrument is f*ked due to a silly electronics design error. We are very sorry, but that is all we can do about it.

  • Black holes suck

    Black holes suck, suck big time, right ? So how can they be so rare today yet teeming in the past ? This extreme physics makes my head want to explode :)

  • There is an interesting article on the same site. They may have discovered how blackholes come into creation.

    http://www.sciforums.com/showthread.php?s=15005939 4ffd628fa19e5ebdb0150148&threadid=2709 [sciforums.com]

  • by Anonymous Coward
    And if you take the estimated mass of the universe and calculate the schwartzchild radius for a black hole of that mass, it's curiously close to the size of the known universe. We are all inside of a black hole right now!
    Cosmological solutions tend not to be like black hole solutions. See the FAQ [corepower.com]. More than that, we don't even really know how to define the notion of a "black hole" in a closed universe, since the standard definition involves whether light inside a region "escapes to infinity". Closed universes don't have an infinity to escape to.
    So maybe the steady state theory for galaxy formation is correct after all.
    Uh, no. Even if we were inside a black hole, particles falling into black holes don't make the interiors of black holes look like steady-state universes.
  • ... and they're doing very well - over budget and waaay behind schedule, but not bad considering that they have to eliminate vibrations from footfalls and distant trucks before they can begin to detect what they're looking for. (The displacements are of the order of a fraction of an atomic diameter.)

    You can read their latest news here [caltech.edu], if you so want.

    (Yes, IAAPA)

  • Reasonably accurate description (according to Hawking's book), but insufficient to explain the evaporation of these holes.
    Quotes from the book (p107-108)
    1) "A black hole with a mass a few times that of the sun would have a temperature of only one ten millionth of a degree above absolute zero. This is much less than the termperature of the microwave radiation that fills the universe (2.7 deg) so such black holes would emit even less than they absorb."

    2) "Moreover, the lower the mass of the black hole, the higher its temperature."

    Therefore super massive black holes have very low evaporation rates and absorb more energy than they emit (at least until this point in time). In an expanding universe that would change far in the future.

    Most of the other explanations down the thread are even worse though - 'they grow until they [spontaneously] explode'!?! Please.
  • Not quite. Here [colorado.edu] is a much better description of what may go on. The current estimates for the age of the universe doesn't give enough time for any black holes to have evaporated away yet. Only black holes with significantly less mass than the Earth could have done so in ~15 billion years. More importantly, there is still matter for black holes to vacuum up, making it even more difficult for them to radiate faster than they can absorb material. Where did they all go? Check the center of your nearest galaxy.
  • I propose that there have been multiple "big bangs" within the same section of space. Then the stellar-sized black holes can be left over from a prior creation (they didn't quite get enough time to evaporate).

    It's silly. There's no real evidence. But I don't know why it couldn't be true. And it gets away from worrying about stars that are older than the universe.

    Caution: Now approaching the (technological) singularity.
  • Well, you're oversimplifying a bit. Yes, there's a major problem with HRC. But the instrument isn't totally useless - they've done a number of clever things to salvage as much science from it as possible, as indicated if you read a bit further in the manual. Yes, it's nowhere near what it was supposed to be, but to say "We are very sorry, but that is all we can do about it." just isn't accurate.
  • Will it have an end? Current thinking seems to think it will expand forever - instead of the "Big Crunch" that everyone was hoping for! Give it long enough and individual atoms will expand to become light-years wide. Shame, as the "Big Cruch" idea nicely fits in with my belief of infinite universes in a never ending cycle of bang/crunch. I'll have to pin my hopes on there being an infinite number of parallel universes instead (I'm bored of this universe. Perhaps in the next I'll be as rich as a king). hehe.
  • in my dryer. it seems to only suck up left socks though. i contacted nasa, they said they would send someone over. he hasn't gotten here yet though.
  • Just because it will expand forever, doesn't mean it won't have an end. Eventually everything will just disipate into heat. Eventually every sun will die and every black hole will fade, and the universe will be a cold, dead place. Even assuming that the human race was still around and we created artificial energy sources powerful enough to sustain us, eventually (WAY WAY WAY in the future) we'd use that all up as well. Even if you could use any raw material for fusion (ala the Delorian at the end of Back to the Future), eventually that will be used up as well. Eventually, it will all end.
  • You have to take into account that most scientists are very careful about their statements.

    Also, when expressed in everdays language, the statements tend to sound more diffuse because that language is not exact enough. I often observe this effect when reading about my field of science in newspapers: I can hardly understand what they mean - I wonder how lay people could ?
  • 500,000 seconds? I could have made this image in about 15 seconds in PhotoShop....
  • mod it you bastards.. a different viewpoint is good.
  • The April Scientific American has an article explaining how a new class of mid-sized black hole is being studied. One theory is that these IXOs (Intermdiate-luminosity X-ray Objects) are the result of the dying of the first generation of stars, which may have been giants because of the simpler structure of the universe.
  • X-ray CCDs don't work the same way that optical do. You don't integrate for long exposures on the CCD chip. Instead the chip is read out very rapidly (100-10000's of times a second depending on the mode).

    The hope is that in any one CCD pixel only one X-ray photon will have fallen during the short exposure - the energy of this photon can be measured by the number of electrons in the pixel.

    Using this method the instrument effectively measures for quantities for each photon: x,y position on the chip, arrival time and energy.

    As the information is this detailed the information spacecraft star trackers (which measure the position drift of the spacecraft) can be used to convert the x,y into Right Ascension and Declination (essentially the position on the sky) of each X-ray photon, which then makes reconstructing into a coherent unblurry image realitively simple

    As an aside to this some of you might have noticed the flaw in the CCD design, which is that if a X-ray source (i.e. a black hole) is too bright then the chances of more than one photon landing in the CCD pixel even when the CCD is read out 10000 times a second is quite high. This problem is caused "pile up", which means that Chandra is pretty bad at looking at bright sources.

    Hope this help!

  • Actually, light from distant stars isn't disappated by anything that doesn't scatter it-- Dust, gases, etc...

    Distant stars appear less bright because light intensity, like most phenomena, drops with the squre of the distance from its source. From a power perspective (and your eyes are power meters, for all intents and purposes), if a star has an output of a hundred trillion megawatts (kinda puny, isn't it-- 100e18 W) and that power is emmitted evenly in all directions, than the power at a receiver (your eye) is directly proportional to the ratio of receiver size to sphere-size, where sphere-size is the size of a sphere with radius equal to the distance between power source and receiver.

    For a star four light-years away, r=9.467e15 meters. Your pupil has a surface area of approximately 1 square cm, or 314e-6 m. That means that your eye is capable of receiving only (280e-37)% of the power that the star produced. For our hundred-trillion-megawatt star, that's 28e-18 W, or -165.5 dBW. That's pretty dim.

    For a sense of scale, if we are on the surface of that star, and it's radius is 1.3e6 km (1.3e9 m, which means that the power output of the star is only 4.7 Watts per square meter), our eyes can detect 14.8e-6 W, or -48 dBW. Obviously *much* brighter.

    In any case, it's obvious that perceived brightness is more a function of distance than anything.

  • by Anonymous Coward
    I think they prefer to be called African American holes BTW.
  • by Captn Pepe (139650) on Wednesday March 14, 2001 @10:06AM (#364994)
    Multiple Big Bangs are allowed -- see Big Crunch. The trouble is, no information is preserved across the singularity, so you can't have structure -- not even singularities like black holes -- come out on the other side.

    Now, in principle you might be able to have a big bang spontaneously occur in our universe, creating a subuniverse -- see Multiverse. Michael Turner has been a big proponent of this lately. However, if this occurred it would either destroy our universe by inflating a huge bubble in it (so points in spacetime that were previously close together would now be separated by billions of parsecs) or you wouldn't see it happen because the new subuniverse would be hidden behind an event horizon (masquerading as an ordinary black hole) and thereby NOT distorting our metric to hell.

    Either way, you don't get an "overwriting" of our universe with a new one. Unless you have a false vacuum decay or something, which is an entirely different issue, and probably a load of crap.
  • In fact, the Hawking lifespan of a stellar black hole is about 10^60 years.

    There might be primordial black holes evaporating now; they started out as sub-earth mass black holes. Nobody's seen this happen yet; see my earlier post.
  • Damn straight. Hawking radiation is thermal, and for a stellar black hole it is in the neighborhood of a nanokelvin above absolute zero -- so the thing is STILL colder than the microwave background.

    Lensing studies have actually detected a few quiescent stellar black holes wandering free in our galaxy, relatively close by at that. Except for the lensing, we detect absolutely nothing from where the black holes should be.
  • These black holes may have formed from large clumps of matter relatively soon after the big bang, or from very early, super-large, short-lived stars. They could then have grown by absorbing matter from their vicinities in the relatively dense universe of the time.

    It seems unlikely that black holes make up much of the dark matter in the universe, although they could be a part. We know by looking at the way galaxies rotate and move, that most of the dark matter is in galaxies, but reasonably evenly distributed through them rather than collected at the center. If this was small black holes we'd notice their Hawking radiation. If it was bigger ones, we'd notice their gravity in various ways.

    No! You were doing great up to the comment about the Hawking radiation. As several people have pointed out, Hawking radiation for stellar black holes is in the neighborhood of a nanokelvin above absolute zero -- colder than the microwave background.

    You actually can have a galactic dark halo composed of black holes, but lensing studies rule out most of the possible mass ranges. Earth-mass primordial black holes are still a candidate, but since they only form by fairly exotic processes a couple of seconds after the big bang, nobody takes them seriously.

    The bit about the super-massive primordial stars is very possibly right on. An upcoming issue of Astrophysical Journal Letters is going to have an article on Pop. III massive black holes, which formed from >100-solar mass stars that formed at the center of primordial density fluctuations. This is very cool -- not only do the resultant black holes do a nice job of nucleating galaxies, but they shine brighly in the early universe before aggregating through mergers into a central supermassive black hole. Neat, yes?

  • I wasn't personally advocating the theory at all. I simply posted the link because it was a quick "anti-blackhole" argument... accurate or not.

    The point of MY post wasn't about the validity of black-holes.

    It was simply used to illustrate a point.

    The fact is, almost every single time some picture of some such new little sparkle is taken, scientists are very quick to yell about how useful this new information is and how they've learned so much.

    If they've learned so much, we wouldn't be seeing articles such as the one you seem to feel so strongly against.

    "Everything you know is wrong. (And stupid.)"
  • In a related article [yahoo.com] astronomers say that as many as 300 billion black holes may have once dominated the early universe. I'm not challenging this statement, but where did they go? I always thought that black-hole-ness was pretty much the end of the line for any chunk of matter. Shouldn't they still be there?
  • Yes! Now I know why the karma whores do what they do: the rush man, the rush!

    Now I'm 4 steps closer to that all important 25, when one gets to post at 2 by default... Actually, I don't like that system, so the 1st post I make when I get there will be a critique of karma and a suggestion to make it 'spendable'...

    Oh, and please please please please don't mod me down as offtopic... I'd hate to lose karma just 'cause I did an 'end zone celebration'... I'll try to be more restrained in the future...
    /me tries to hold in the excitement...

    /me fails....

    Woo hoo! In your face signal 11! Who's the karma whore now, yeah? yeah? I'm talking to you, dude.... ;)

    -----
    IANASRP- I am not a self-referential phrase
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  • In a word, no. Only black holes in the last fraction of their life-span produce enough Hawking radiation to be noticed, and there is no obvious source for black holes small enough to be decaying now.
  • To follow up on the previous, Chandra has star trackers which allow the telescope to point pretty well, though not to Hubble like accuracy. Chandra is also on an orbit (unlike Hubble) which allows it spend a long time away from the earth, this means you can point at something for a long time and not worry about the earth getting in the way.

    The second thing to note is that Chandra is an X-ray telescope. Each individual X-ray photon is detected and its position and time of arrival (along with energy) are logged. So, all you have to work out is where the telescope was pointing when the event landed, and you can reconstruct the image.

    I love working in a field where you name individual photons.

  • Then but what happens with the one that goes in?


    ---
  • There are actually several ways to come up with some estimate of how much mass is dark -- ie, "missing," though I hate that term.

    The key thing is that, for a given system, you come up with some way to determine the total mass, and then compare that with the luminous mass (ie, the stuff you can see) -- that's really all it comes down to. The trick, of course, is in figuring out a way to get that estimate of the total mass.

    There are several possible solutions. If you're looking at some systems (like, say, a cluster of galaxies), you can look at the "velocity dispersions" of the component galaxies, and from those (and using the assumption that the cluster has more-or-less virialized) get an estimate of the total mass that is "pulling" on each galaxy. You can also use gravitational lensing, as suggested by another poster. With clusters, you actually have another (very spiffy) option, which is to look at the X-ray emission from the hot gas between the galaxies in the cluster -- the temperature of the gas, which relates to the X-ray luminosity, is also related to the mass of the cluster.) The results with all of these methods suggest that a great deal of the mass in large clusters of galaxies is non-luminous.

    In our own galaxy (and others), you can do a similar sort of analysis and come up with the same sort of result (that much of the mass must be dark). (Here, the usual procedure is to form a "rotation curve," which shows the velocity as a function of radius from galactic center; if you do this, you find that the radial velocity "flattens out" and stays that way for much longer than we'd expect unless there is a substantial "dark" mass in a halo surrounding the galaxy.) It's a little dangerous to make comparisons like these, since it's possible that the source of "extra" mass may be different on large (ie cluster) and small (ie galaxy) scales, but the basic idea is the same: that a big, big chunk of the matter in the Universe is probably not luminous.

    A large answer to a short question. :-)

  • Suppose I'm sitting on my porch, taking a long exposure of something many miles away. (Err, I live on a mountaintop, and it's dark. Or something like that.) And suppose that while I'm taking the picture, I pace nervously back and forth across my porch, holding the shutter open all the while, but keeping my camera pointed at that distant object the whole time. No problem, right? The object will appear to change slightly as I view it from different angles, but if the distance between me and it is much much greater than the width of my porch, the effect is negligible.

    Same sort of deal here. Chandra can remain pointed to reasonably high accuracy on something as it moves in its orbit. Sure, it's moving (and so is the Earth, and so is the distant object, etc.), but as long as the telescope remains pointed at the object in question, you're fine.

  • WOW! 300 Billion early-universe black holes. At 12 billion years ago, that puts the age of the universe at a few billion years old. That would be enough time for some early supermassive objects to form, collapse under their own G's, create SMBH's and then evaporate?I could see how this would be possible if the universe was the size it was today but at roughly 20% the size, the SMBH's would have greater probability of 'eating' regularly, unless, the rate at which energy condensed to matter was slower than the rate at which SMBH's need 'food' to remain. If this was the condition, then the SMBH's would eventually evap and the cosmic sea could fill with cooling energy/matter. I don't believe it was such a high #. PB
  • but basically we are all just specualting nobody really knows
  • also a good point , but it just seems like these guys come out and say these things then pretend that this is the be all and end all , a little humility on there behalf would be nice to see , but then they would probably lack credability in there claims , so i supose that is the stance they have to take just to get recongnition and validation of some kind
  • No, do you really care ? i didnt think so

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