Slashdot is powered by your submissions, so send in your scoop

 


Forgot your password?
Close
typodupeerror
×

Survey of Super Massive Black Holes Completed 169

Posted by Zonk from the now-we-know-where-not-to-go dept.
eldavojohn writes "NASA has announced the completion of a survey of nearby supermassive black holes. Every galaxy that revolves around a supermassive black hole within 400 light-years of our own galaxy has been cataloged. From the article: 'Called active galactic nuclei, or AGN, these black holes have masses of up to billions of Suns compressed into a region about the size of our solar system. The all-sky census, performed using NASA's Swift satellite over a nine-month period, detected more than 200 nearby AGN.' I'm starting to feel very lucky to have grown up in the Milky Way Galaxy."
This discussion has been archived. No new comments can be posted.

Survey of Super Massive Black Holes Completed More

Survey of Super Massive Black Holes Completed

Comments Filter:
  • The average density of a supermassive black hole can be very low, and may actually be lower than the density of water.

    I'm starting to feel very lucky to have grown up in the Milky Way Galaxy.

    He might as well be saying he feels lucky that he grew up in Kansas instead of Hawaii.
    • Considering our space boffins have a problem seeing large asteroids really close up -- not even one light second away -- http://www.cnn.com/2002/TECH/space/06/20/asteroid. miss/ [cnn.com] why should we believe that they have seen all the black holes many light years away?

    • Re: (Score:2, Insightful)

      by Tablizer ( 95088 )
      The average density of a supermassive black hole can be very low, and may actually be lower than the density of water.

      That sounds suspicious, especially coming from wikipedia. Something with a density that low could not likely bend light enough to keep it from escaping, even if very large.
             

      • Density of black holes (Score:5, Informative)

        by Harmonious Botch ( 921977 ) on Sunday October 08, 2006 @03:47AM (#16353399) Homepage Journal
        The average density of a supermassive black hole can be very low, and may actually be lower than the density of water.

        That sounds suspicious, especially coming from wikipedia. Something with a density that low could not likely bend light enough to keep it from escaping, even if very large.

        The singularity that bends light does not have that low density. It has an incredibly high density. But the AVERAGE density is the mass of the singularity divided by all that space inside the event horizon.

        • Re: (Score:1)

          by Beale ( 676138 )
          Bad Analogy O'Clock: Defining the size of a black hole by it's event horizon is like defining a river by its watershed. The actual physical object is a point in the middle, not the large sphere of non-escaping stuff around it.

          • Re: (Score:1)

            by gedhrel ( 241953 )
            By what definition of "actual" and "physical" (and "is")?

          • Re:Density of black holes (Score:4, Informative)

            by GeffDE ( 712146 ) on Sunday October 08, 2006 @09:13AM (#16354363)
            No, the actual physical object is the volume inside the event horizon. Why is it called a black hole? Because anything that entered the event horizon does not escape. So a black hole is the volume enclosed by the event horizon. The singularity is the extraordinarily dense pit of gravity at the center of a black hole. They are two different things. Defining the size of a black hole by its event horizon is...how it should be done, if you think about it. The "object" in the middle is was causes all the action to happen, but that doesn't make it the only part of a black hole.

          • Re: (Score:2, Interesting)

            by Omnifarious ( 11933 ) *

            The actual physical object is a point in the middle, not the large sphere of non-escaping stuff around it.

            So, you've seen this thing in the middle? What's it look like? Enquiring minds want to know!

            You are possibly a troll, but it's rather standard to define the size of a black hole by the size of its event horizon. This is largely because we can't actually know anything about what there is behind the event horizon. Maybe there's a singularity there, and maybe there isn't. What we know of physics s

      • Re:relativity (Score:5, Informative)

        by ajs ( 35943 ) <ajs.ajs@com> on Sunday October 08, 2006 @06:50AM (#16353897) Homepage Journal
        That sounds suspicious, especially coming from wikipedia.

        It would sound more reasonable coming from Slashdot? What source of information on the Web do you think is more reliable? I've certainly fixed my share of errors on Wikipedia, but that's becuase I hunt them down, as do many others. That kind of fact-checking is almost non-existant on most of the Web, so if I'm going to trust any one source (and I don't) for such information, it would be Wikipedia.

        And, as others have noted, you were mis-understanding the definition of "average density". There's a fairly well-known calculation that states that a spherical volume of material with the density of water, and a diameter less than that of Jupiter's orbit would form an event horizon, effectively constituting a black hole. It's a nice visualization of a complex phenomenon. R. Huber has done the math for us [chestnutcafe.com] (pdf) if you want to check for yourself.

      • Re: (Score:3, Informative)

        by Impy the Impiuos Imp ( 442658 )
        Suspicious? Let's see. "The solar system"/supermassive black hole is about 16 light-hours across.

        57600 light-seconds

        10713600000 miles

        The sun is 800,000 miles across. So, width-wise, the solar system is

        13392 suns wide

        Volume is the cube of the linear width, so the solar system could fit

        2,401,797,132,288 sunc

        in its volume.

        Although the density of the core of the sun is very high, I'm thinking it's not so high that "billions" of suns would make such a volume be denser than water when that volume could hold tw

      • Re:relativity (Score:4, Informative)

        by Ckwop ( 707653 ) * on Sunday October 08, 2006 @10:36AM (#16354765) Homepage
        That sounds suspicious, especially coming from wikipedia. Something with a density that low could not likely bend light enough to keep it from escaping, even if very large.

        It's nice to see a skeptic; It's a virtue to be a skeptic and not a sin. However, in this case your skepticism is misplaced.

        The simplest black hole solution to the equations that govern General Relativity is Schwarzschild's solution. In this he shows that the radius of a black hole is directly proportional to its mass. Elementary geometry tells us that the volume of a sphere is proportional to the cube of the radius. Therefore, the density, which is just mass over volume, that is required to create a blackhole decreases the more mass you have.

        I find the figure fairly reasonable for the amount of mass these super-massive black-holes contain.

        Simon

  • 400 light years isn't that far... (Score:5, Informative)

    by mhotchin ( 791085 ) <<slashdot> <at> <hotchin.net>> on Sunday October 08, 2006 @02:50AM (#16353181)
    400 lightyears? Didn't the submitter read the article?

    It's 400 *million* light years.
    • Yeah, no kidding. I was reading the Slashdot summary and I was thinking "Exactly how many galaxies are we supposed to think are within 400 light-years of ours? Especially considering that the diameter of our galaxy is 100,000 light-years?"

      • Re:400 light years isn't that far... (Score:4, Informative)

        by CodeBuster ( 516420 ) on Sunday October 08, 2006 @04:02AM (#16353461)
        Indeed, the nearest major galaxy in the local group is actually the Andromeda [wikipedia.org] Galaxy at ~2.5 million light years distance, give or take a few thousand since the distance can only be measured relatively indirectly via Cepheid [wikipedia.org] variable stars. The Andromeda galaxy is also thought to be on a collision course with the Milky Way (although it is impossible to know for sure if they will actually collide because the tangential velocity of the Andromeda Galaxy with respect to the Milky Way is not known). So, assuming that some other disaster does not befall humanity in the meantime, which would certainly be miraculous given our recorded history and more recent events, we will know the answer in ~3 billion years or so (predicted time to impact or convergence rather since both galaxies are mostly empty space).
        • > since the distance can only be measured relatively indirectly via Cepheid [wikipedia.org] variable stars.

          Well, if you can get a rough estimate of the size of our galaxy, you could judge the distance to the Andromeda galaxy via angular size, assuming they are roughly in the same ballpark of size.

        • Re: (Score:2)

          by suitti ( 447395 )
          A new technique, involving looking for eclipsing binary stars in the target galaxy, has been used to measure the distance to m33. m31 is next. This technique is still based on the brightness of stars, but the intrinsic brightness is supposed to be better known.

          Also of interest is that proper motion has been measured for m33. No proper motion has yet been detected for m31.

      • "You humans, when're you gonna learn that size doesn't matter? Just 'cause something's important, doesn't mean it's not very, very small."

    • Re:400 light years isn't that far... (Score:5, Interesting)

      by forgotten_my_nick ( 802929 ) on Sunday October 08, 2006 @04:02AM (#16353455)
      Exactly.. here is a nice video to put the whole thing in perspective.

      http://www.youtube.com/watch?v=mcBV-cXVWFw [youtube.com]

      • Re: (Score:1)

        by jftitan ( 736933 )
        I've always been one looking up into the stars, but never have I heard or seen anything as awesome as this youtube clip. What I don't understand is... our universe is 250 billion lightyears in size? I thought we couldn't measure our universe? I mean I know our galaxy is... huge! and our solar system is roughly... less huge (HAHAHAH big numbers!)

        Have we been able to size our Universe? because if that has happened WTF has happened to all the news about it. "Tonight at 11! The universe gets a size, and

        • Re: (Score:3, Insightful)

          by empesey ( 207806 )
          > I thought we couldn't measure our universe?

          Really, we only have to measure half of it and multiply 2.

      • The narrator on the video keeps going on about look 78 billion light years into the universe but that is wrong. The universe only formed 13.7 billion years ago so the furthest we can see is 13.7 billion light years due to relativity. Inflation may mean the Universe is bigger bit we will not be able to see it if it is.

        In actual fact the WMAP probe is the furthest we have seen, NOT the Hubble deep field since that looks at the Universe ~300k years after the Big Bang before there were any stars, let alone g
    • If you're gonna say that, you need to do that Dr Evil pinky thing.
    • Maybe we should tag this article (and such future errors) 'erroneous' or something, so that they'll get fixed?

  • I'm starting to feel very lucky... (Score:5, Funny)

    by RyanFenton ( 230700 ) on Sunday October 08, 2006 @02:51AM (#16353185)
    I'm starting to feel very lucky to have grown up in the Milky Way Galaxy.

    Yes. Living near one of those super-massive black holes would certainly suck. Being one with everything around you sounds nice and radiant - but it leaves you all strung out over time, and it seems to take forever! The light at the end of the tunnel is you.

    Ryan Fenton

    • Re: (Score:2, Interesting)

      by Oronar ( 942125 )
      I guess it sucks for you then.

      Because there's a supermassive black hole at the center of our galaxy.
      http://en.wikipedia.org/wiki/Sagittarius_A* [wikipedia.org]
      • Ask not up whom the black hole sucks...it sucks up you.

        (Parent is right, btw. There's at least one multi-million solar mass black hole within 70K light-years of you. It holds the core of our galaxy together.)

    • Re: (Score:2)

      by ajs ( 35943 )
      It would not suck, and we do live near one. It's questionable how much living near an active galactic core would suck, but we'll find out eventually when something hefty gets munched by our galaxy's black hole.

    • Re: (Score:2)

      by Ruie ( 30480 )
      I'm starting to feel very lucky to have grown up in the Milky Way Galaxy.

      Our black hole is located near Sagittarius A.

  • 400 light years?!?! (Score:4, Informative)

    by philgross ( 23409 ) on Sunday October 08, 2006 @02:51AM (#16353187) Homepage
    That would be 400 million light years. 400 light years wouldn't get you out of our local arm of the Milky Way.

    • Re: (Score:3, Funny)

      by heatdeath ( 217147 )
      It's a good thing we have an army of a millionth of an editor keeping slashdot submissions high quality.
  • I can't be the only one that thought of the british band, "Muse" =D
    • I can't be the only one that thought of the british band, "Muse" =D

      Or goatse :-)
      • I was thinking about some african-american pornstar called jeannie pepper.
        Damn that one got real big in the last ten years.
    • Yeah - and it came up on iTunes for me just as I read the headline which was odd!
    • "I can't be the only one that thought of the british band, "Muse" =D"

      Nope, you aren't. Me and my GF had a laugh when we saw the headline. "Glaciers melting in the dead of night and the superstars sucked into the supermassive..."
    • 1 : what prick modded you offtopic? meh,

      2: I think I need to give these guys a bell as there's a supermassive black hole on my desk right now ^^

  • We Live in a (semi-)Active Galaxy (Score:3, Informative)

    by idsfa ( 58684 ) on Sunday October 08, 2006 @02:52AM (#16353199)
    Hate to break it to you, but there's a >million solar mass black hole at the center of our galaxy. We're not considered an "Active Galaxy" only because it is on a diet [nasa.gov].
    • Hate to break it to you, but there's a >million solar mass black hole at the center of our galaxy. We're not considered an "Active Galaxy" only because it is on a diet.

      Hate to break it to you, but, er, that information's actually a little out of date...

      Hey, where the hell did all the puppeteers just go?

      -- B. Shaeffer

  • They are black and holey

  • Why is he feeling lucky? (Score:4, Interesting)

    by maroberts ( 15852 ) on Sunday October 08, 2006 @02:54AM (#16353213) Homepage Journal
    Almost every major galaxy including the Milky Way has been found to have a supermassive black hole at its core. The only lucky part is our sun not being near to the core of the galaxy, not which galaxy it is in.
    • Yeah, I was going to comment on that same thing... We got an aprox. ~2.6 billion solar-mass black hole according to our latest calculations. (From amongs other things observing stars orbiting rather close to it)

    • Re: (Score:2)

      by Entropy ( 6967 )
      He is probably feeling lucky because the supermassive blackhole at the center of our galaxy is not an AGN .. not active. Not "feeding". Of course, given that the article says only a few percent are active, it's not exactly "lucky". *shrug*
    • That's like saying "Isn't it lucky we live on a planet which has water to drink!"; it's not "lucky", we could only have evolved on a planet which had water to drink.
      • This is known as the Anthropic Principle [wikipedia.org].

      • Re: (Score:1)

        by gomoX ( 618462 )
        If we were unlucky enough we could have evolved on a planet were the timing for our understanding of supermassive black holes and the annihilation of our solar system were perfectly synchronized. Actually, given the amount of different "universes" there are out there (observable universes) this is very likely to happen somewhere at some point.
  • Our galaxy is about 100,000 light years in diameter [hypertextbook.com]. Every galaxy that revolves around a supermassive black hole within 400 light-years of our own galaxy has been cataloged.

    Given the size of our galaxy, just how many other galaxies are within 400 lightyears of us, AGN or not? Or am I just massively confused here?

    • Re: (Score:1)

      by Tablizer ( 95088 )
      just how many other galaxies are within 400 lightyears of us

      Thousands, according to this website [galaxieclub.com].
             
  • In an era where there's no funding for anything, where I'd like the secrets of the universe revealed in my small lifetime, I'm genuinely excited that observations and projects like these are being conducted. Thank you NASA. I'll add that I wish that NASA's budget wasn't so tied to defense subsidy. Science for science's sake is a dream I hope we achieve soon.

    • Re: (Score:1)

      by gomoX ( 618462 )
      That's not gonna happen. The axis of evil doesn't wan't you to know the secrets of the universe, because they are *evil*. They must be terminated. Now give me all your science budget for my military program please.
    • > In an era where there's no funding for anything

      An odd statement given the US government is spending $2 trillion (with a T, not a B or M) per year, a rate that, adjusted for inflation, exceeds per capita any other year in history except for one year during WWII, in which we were engaged in two major war fronts simultaneously and were building a major capital ship per week.
    • To quote Star Trek (specifically Q, in the last episode of TGN), the future is "not mapping stars and studying nebula but charting the unknown possibilities of existence."

      This isn't science for science's sake. Figuring out how things work is science for science's sake. This is science for scientists that are hunting for something to figure out; it's science for accountancy. I'm not sure that this isn't worse than science for practical applications.

      Which do you think kills the imagination faster? Busy-wo

  • Family Feud? (Score:3, Funny)

    by KewlioMZX ( 992347 ) <kewlio-origin AT simguy DOT net> on Sunday October 08, 2006 @03:12AM (#16353275) Homepage Journal
    100 black holes surveyed, top 5 answers on the board...

  • Wrong (Score:5, Interesting)

    by WhiteSpade ( 959060 ) on Sunday October 08, 2006 @03:23AM (#16353315)
    The article says that it is every super massive black hole within 400 million light years. Also, as for being "lucky" to be in the Milky Way, our Galaxy has a super massive black hole at the center of it. Actually, we are a very typical galaxy. We are slightly larger than the average and we are a spiral galaxy (there are more elliptical galaxies and irregular galaxies than spiral). We are very typical. Also, as for being lucky about not being closer to the center of the galaxy (someone above mentioned that as well) if we were closer to the black hole at the center, it would not mean much. We are in an orbit around it and thus we won't be falling into it any time soon, even if we were closer to it. We do, though, have a great location in the galaxy. We are far enough out that we can look across the plane of our galaxy (only at some wavelengths because dust obscures a lot) and get a good view of it. We also can look out pretty well too. And to make things even cooler, our solar system actually bobs up and down through the main plane of the galaxy. It take about 30 million years to complete a complete cycle, but in 5 or so million years we will have a pretty cool view from above of the Milky Way. I don't remember exactly what the angle is that we would be viewing the galaxy from, not huge, but enough to be useful. The point of all this is that the advantage of this survey is to have a complete list of super massive black holes so as we are testing out theories we can apply these theories (and how they measure up) across not only a wide data set, but also a very complete set. There is so much left to be learned about black holes and this catalogue will certainly help.

    • Re: (Score:2)

      by jamesh ( 87723 )
      One good thing about being out where we are (the unfashionable end :) is that there should be less crap flying around to crash into us, eg like other solar systems.
    • It probably says a lot about me that I just thought "Wow! Only 5 million years! I can hardly wait!"

      24 years down, 4,999,976 to go!
  • Now if they will announce a completion of a survey of super Miniature fundamental particles...

  • "NASA has announced the completion of a survey of nearby supermassive black holes. Every galaxy that revolves around a supermassive black hole within 400 light-years of our own galaxy has been cataloged.

    I'm sure they didn't get every galaxy... You know how things go with censuses; there were probably some galaxies that didn't care about it and claim the form they sent back was lost in the mail or something.

  • The other galaxies are nowhere near as tasty!

    But, today I learned an interesting fact about the milky way bar [wikipedia.org].
  • Unfortunately, the survey everything but a a success. From the many questionnaires sent out by NASA, none of the black holes returned a completed form. Fortunately, NASA seems to learn from its mistake. The next questionaire will have much less and easier questions which should dramatically increase the response ratio.

    • Re: (Score:1)

      by Ed_1024 ( 744566 )
      Ah but they DID fill in the questionnaires - unfortunately the postmen can't make it back past the event horizons. Maybe they should start examining the Hawking Radiation for replies...

  • There are no black holes (Score:5, Interesting)

    by viking80 ( 697716 ) on Sunday October 08, 2006 @03:53AM (#16353413) Journal
    First, the diameter of a "black hole" is proportional to its mass. The sun, for example, must be compressed to a diameter of about 3km to become a black hole. A black hole with the mass of billion suns would have a dameter=3 billion km or 1000 times our solar system. The density of this black hole would be "low" as in much thinner than air. (Do the math yourself. Mass of sun is 2x10E30kg)

    Anyway, as a region of space gets denser, time slows down, and as the density approaches the density required to become black hole, time just freezes.

    What you will see when looking at a "black hole" is just a region of space with the eventual event horizon of the hole just frozen in time, and as you move outside, time goes through the "molasses" stage, and as you get further away, gets normal.

    The black hole will not form in any finite time since time there just stopped!

    For the observer falling towards the "hole", time in the rest of the universe just speeds up. In a matter of minutes the universe will age billions of years, and the observer will first hand know the ultimate fate of the universe in a distant future.

    • Re: (Score:1)

      by 72Nova ( 935275 )
      So here is a common misconception. The "size" of the blackhole that you are talking about is it's Swarzchild radius, which has nothing to do with where the mass actually is. Nearly all of the mass is compacted into a tiny volume at the center. The Swarzchild radius is simply the point at which anything that comes closer will inevitably fall into the center, and has no way of escaping. Black holes do form in finite amounts of time. An observer, or any mass, which is falling into the blackhole will not
    • That is considering the observer's vantage point remains stable until the end of the universe...

      I expect that if you were close enough to a black hole to experience time outside going by whizzingly fast WITHOUT you being torn apart by gravitational forces it would indeed be quite a show, but just as likely some other object would whiz right into you billions of years hence and your lookout would end.

  • On Purpose? (Score:3, Insightful)

    by tokki ( 604363 ) on Sunday October 08, 2006 @03:54AM (#16353415)
    I wonder if the editors purposefully put factual errors in there just to sit back and watch the orgie of "OMG NO THATS WRONG" comments that invariably follow. 400 light years? Of course it's a mistake. Is there anyone who reads /. that doesn't know that 400 light years is a little close for a galaxy? Of course, there are those that get positively horny over the propsect of correcting factual errors.

    Because hey, trivia = intelligence, right?

    • Re: (Score:2)

      by Tim C ( 15259 )
      Is there anyone who reads /. that doesn't know that 400 light years is a little close for a galaxy?

      Yes, I'd expect most of the readership to not realise that in fact. This is a general techy website, not an astro one. Would you expect most people here to know how solar cells work, or how to construct a thermocouple?
      • Yes, I'd expect most of the readership to not realise that in fact. This is a general techy website, not an astro one. Would you expect most people here to know how solar cells work, or how to construct a thermocouple?

              Perhaps not. But I'd expect someone who is consolidating this information to at least do rudimentary fact-checking so as to not spread misinformation.

      • Re: (Score:2)

        by tokki ( 604363 )
        You really don't think that something that anyone who payed attention in 7th grade science class (which would be just about any /. read) would pick up a little bit of a sense of galactic scale? I think you underestimate the comprehensive ability of the readership, or you overestimate yours (or both).
  • Was that the Fleet of Worlds [wikipedia.org] that just zoomed past?
  • It seems to me that humans wouldn't have evolved on Earth if these super massive black holes were not located at just the right distance.

    It reminds me of the series finale of Star Trek TNG.
  • Read Me now! [electric-universe.org]

    Yes, it does make a difference. (-:
  • So it wasn't aliens abducting people and probing their asses all these years.

  • The catalog (karma whoring) (Score:3, Funny)

    by nyri ( 132206 ) on Sunday October 08, 2006 @06:14AM (#16353801)
    Every galaxy that revolves around a supermassive black hole within 400 light-years of our own galaxy has been cataloged.

    The whole catalog:
    1. Our own galaxy
  • 400 light years is a tad close for Active Galactic Nuclei...
  • That's not a Super Massive Black Hole. It's a space station!
  • They black holes who answered the survey overwhelmingly disapprove of the Bush Administration. Most blame Bush directly for their woes. "George Bush doesn't care about black holes" was a common sentiment.

    Blame for Dick Cheney was surprisingly sparse, despite the gravitas he added to Bush's presidential bid in 2000.
  • The survey was apparently completed so quickly because it simply consisted of the question "How much do you suck?"

  • 'Called active galactic nuclei, or AGN, these black holes have masses of up to billions of Suns compressed into a region about the size of our solar system. The all-sky census, performed using NASA's Swift satellite over a nine-month period, detected more than 200 nearby AGN.'

    This is wrong. Active Galactic Nuclei are not the same as supermassive black holes. AGN are cases where one of these supermassive black holes is actively accreting on a large scale. The result is an accretion disk which shines brigh

Slashdot Top Deals

Get hold of portable property. -- Charles Dickens, "Great Expectations"

Close