Stories
Slash Boxes
Comments
Search

News for nerds, stuff that matters

Slashdot Log In

Log In

Create Account  |  Retrieve Password

Astronomers Make Important Dark Matter Discovery

Posted by Zonk on Tue Aug 15, 2006 11:26 AM
from the matter's-goth-sister dept.
Space Science
saudadelinux writes "To quote a press release on NASA's site, astronomers using the Chandra X-ray Observatory have discovered 'how dark and normal matter have been forced apart in an extraordinarily energetic collision.' There will be a briefing at noon, August 21 ET, on this discovery, with streaming media provided by NASA, and some details of the research posted on Harvard's Chandra site just beforehand."
+ -
story

Related Stories

[+] Dark Matter — "Alternative Gravity" Team Responds 215 comments
An anonymous reader writes, "Following previous results, an international team of astronomers answers, defending the case for a modification of the theory of gravity. This article presents an alternative to dark matter and states constraints on the neutrino mass. In short, dark matter is still not a necessity, provided that neutrinos weigh 2eV. This is allowed by what we currently know and should be tested in the KATRIN experiment in 2009."
This discussion has been archived. No new comments can be posted.
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.

Astronomers Make Important Dark Matter Discovery 50 Comments More /

 Full
 Abbreviated
 Hidden
More
Loading... please wait.
  • I don't know exactly why, but whenever I hear about dark matter, I'm reminded of Zippy The Pinhead.
    • I don't know exactly why, but whenever I hear about dark matter, I'm reminded of Zippy The Pinhead.


      The real question: Is NASA having fun yet?

    • Think that's bad? (Score:3, Informative)

      by jd (1658)
      In recent studies of deuterium in the galaxy, they're finding less than 1/25th of what they're expecting, and almost entirely in the wrong places. They therefore conclude that there must be MORE than what they expect, but in a place/form that is invisible.


      Will Hannibal Lector please stop eating the brains of astrophysicists.

      • IAAAstrophysicist, so perhaps a good chunk of my brain has been consumed already, but are you certain you mean *deuterium*? Is there a cite for this? I worked on galactic chemical evolution, and I'm a little out of touch with recent developments in the field, but this is news to me. Or maybe we're all really as dumb as you think we are.

          • Re:Think that's bad? (Score:4, Informative)

            by TrekkieGod (627867) on Tuesday August 15 2006, @03:12PM (#15913070) Homepage Journal

            I'm not an astrophysist, nor was I involved in the conversation before now, but I did read your linked article :)

            Thanks for posting it, btw. I was taking what the parent said for granted, and it sounded pretty bad, but now it looks like it was a combination of bad reading comprehension and badly worded writing. The article you linked to at least, doesn't claim scientists are finding less deuterium than they expected and therefore expect more. Quite the contrary, they're finding a lot more than they expected, and thus are deciding that their theories need to be changed. I quote:

            scientists had assumed that at least a third of the primordial deuterium present in the Milky Way was destroyed over time as it cycled through the stars...but FUSE found deuterium exists in amounts less than 15 percent below what was there originally.

            So, they thought there were massive amounts of deuterium was "destroyed" and that not as much was left. Destroyed is a pretty bad way of describing it, but they allude to it in the article that what they mean by it is, "was transformed into heavier elements by stellar fusion." Instead, they're finding out that the amount of deuterium in the galaxy now is only about 15% less than what they thought was the original amount available. They also mention it being in unexpected places, or rather, not distributed evenly, which they find unusual according to current theories.

            Nothing to complain about here. Seems to me that the astrophysicists still have their brains intact, and realize their theory needs to be tweaked if it doesn't match the evidence.

      • Re:Think that's bad? (Score:5, Informative)

        by The Great Pretender (975978) on Tuesday August 15 2006, @12:58PM (#15911602)
        There was a recent article in Discover [discover.com] that profiled a physist (Mordehai Milgrom) who had come up with modification on Newtons law to explain the planets orbits (forgive me, I'm a layman in this but it seems that dark matter started as a way to explain the weird plant orbits in extended galaxies - I encourage you all to correct me).

        "Mordehai Milgrom never wanted to be a heretic. Twenty-five years ago, while poking around for a meaty research problem, he found one that changed the course of his career--and that might yet transform our most fundamental understanding of the universe. His ideas, long relegated to the fringes of physics, where all but cranks fear to tread, have finally become too intriguing for his mainstream colleagues to ignore. Milgrom's heresy? He denies the existence of dark matter, the shadowy and thoroughly hypothetical stuff generally held to make up 80 percent or more of all matter in the universe. Even though dark matter has eluded all attempts at detection, most cosmologists are convinced it must be out there."

        So potentially there may not be any dark matter and the vast money being spent on it's pursuit is being wasted. For the record I don't believe in string theory either. I have to say that I would love to subscribe to the simplicity of Milgroms ideas, but it's just a gut check that fitting the theory to the data is better than creating a fudge factor - which dark matter ultimately seems to be.

  • Nothing to see, move along (Score:5, Insightful)

    by dreamchaser (49529) on Tuesday August 15 2006, @11:28AM (#15910905) Homepage Journal
    How about waiting for the 21st and THEN posting a story. There is literally nothing of substance yet. Oh wait, this is Slashdot. We'll just have it posted again in two days, then on the 21st, then on the 25th, etc.
  • If you shine a torch at some dark matter what does it become?

    Isn't dark matter just all the none illuminated items in the universe?
    Rocks and stones and humans and plants and animals and silicon and paper and all these things are what I would consider dark matter, I might be wrong but someone could add some illumination on the subject I would be most grateful.

    • Re:Question. (Score:5, Informative)

      by dreamchaser (49529) on Tuesday August 15 2006, @11:30AM (#15910929) Homepage Journal
      A small portion of it is rocks, dust, etc. Prevailing theories hold that much (most) of it is made up of non-baryonic matter which has yet to be observed.

        • Re:Prevailing theories (Score:4, Insightful)

          by dreamchaser (49529) on Tuesday August 15 2006, @01:17PM (#15911788) Homepage Journal
          It *is* possible that future advances in astrophysics and cosmology will nullify the dark matter argument. It's just as likely that there *is* some sort of mass carrying matter out that that we have yet to identify. Either way it just shows how much we have left to learn.

    • Re:Question. (Score:5, Funny)

      by Silver Sloth (770927) on Tuesday August 15 2006, @11:35AM (#15910973)

      Humans, at least alive ones, are not at zero degrees K, and therefore radiate energy, not much, but some. We might be said to be dim matter.

      http://en.wikipedia.org/wiki/Dark_matter [wikipedia.org]This link will tell you more.

    • Re:Question. (Score:5, Informative)

      by SupremoMan (912191) on Tuesday August 15 2006, @11:38AM (#15911004)
      Not at all sir. http://en.wikipedia.org/wiki/Dark_matter [wikipedia.org]This should enlighten you a bit.

      In cosmology, dark matter refers to matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation (light) to be detected directly, but whose presence may be inferred from gravitational effects on visible matter such as stars and galaxies.

      It's a blanket term used for stuff in the universe we think is there but haven't seen because we can not detect it's presence.

        • Re:Question. (Score:5, Insightful)

          by Mike Peel (885855) on Tuesday August 15 2006, @12:20PM (#15911302) Homepage
          "And this is different from believing in God... how, exactly?"

          We look for explanations of what's going on, not just saying "it's God. Don't go there." Think of dark matter as a placeholder, not the end product. Over time, we should find a reasonable explanation of what's causing the discrepancy, at which point it will just become part of the "normal" physics.
          • Ever read Roger Zelazny's "Lord of Light". In one of the chapters there's a story about battling an enemy that looks like a demon, is strong as a demon, is fast as a demon, etc.. It's not a called a demon, however. One character asks why they make the distinction when it doesn't matter how they go about fighting it (i.e., if it walks like a duck). The other character responds that it is all the difference. To say that it's a demon would be equivalent to "bowing down to the unknown". I.e., dispensing with s

        • Re:Question. (Score:4, Funny)

          by farker haiku (883529) on Tuesday August 15 2006, @12:26PM (#15911341) Journal
          And this is different from believing in God... how, exactly?

          Apparently, when you seperate dark matter from normal matter you get an extraordinarily energetic collision, whereas when you seperate a Christian from God you get a rational thinking being.
          • whereas when you seperate a Christian from God you get a rational thinking being.

            Not at all. Irrational people will continue to believe what they always have, and continue to be irrational, whether or not religon is involed. It just gets popularly scapgoated, by people who have some ax to grind in the first place.
        • "And this is different from believing in God... how, exactly?"

          There is no secondary 'effect' that infers the existance of god.

          Be that as it mey, what this means is 'we have observed and effect, now we are looking for the cause.
          They seem to be making head way.

          Something falling is an effect of gravity. Oberving that effect is what lead to discovering all the cool stuff about gravity.

        • Re:Question. (Score:5, Insightful)

          by Anonymous Coward on Tuesday August 15 2006, @12:35PM (#15911406)
          Because the flow of information is reversed- scientists infer the nature of dark matter from indirect observations of secondary effects. If there wasn't evidence from these secondary effects, then these inferences would be wrong, and scientists would have to come up with a new theory. Sure, there are some scientists who have a lot invested in dark matter, just as there were many prominent scientists who built their careers on the study of luminiferous aether or phlogiston. Time, and science, proved them wrong.

          Religionists, OTOH, believe in a Supreme Being a priori, and attribute whatever they cannot otherwise explain to the "mysterious ways" of the divine. The edifice of cosmology would withstand the discovery that there is no dark matter. Would religion be able to withstand the discovery that there is no God?

        • And this is different from believing in God... how, exactly?
          Believer: There's something we can't explain. God did it.

          Scientist: There's something we can't explain. Let's try to figure out what it is.

          Believer scientist: There's something we can't explain. Let's try to figure out what God did.
        • By "not seen", we just mean that it doesn't *glow* like stars, not that it can't be detected at all. In fact, we detect it by the gravitational influence it has on neighboring luminous matter as well as lensing the light of background objects. We can study its large-scale nature and distribution fairly well, just not the composition or small-scale structure yet.
        • Because next week, we'll have a better answer.

          And next year, even better.

          And next century, better still.

          You may now switch argument tactics to "How can you trust science if it keeps changing its answers! Religion has been giving the same answer for thousands of years!"

    • 'Dark' is a code word for 'We don't know.'

      Seriously.

  • Together again (Score:4, Funny)

    by Petskull (650178) on Tuesday August 15 2006, @11:30AM (#15910925)
    Now dark and normal matter will be one big family again, obviously with court supervision.

  • Measure DM (Score:5, Funny)

    by MECC (8478) on Tuesday August 15 2006, @11:36AM (#15910975)
    As long as NASA doesn't try to measure DM in metric units, everything should go just fine.

  • In Soviet Russia, dark matter discovers YOU!

    Although In Soviet Russia, the presentation would probably be posted before the story.

  • Please record (Score:5, Funny)

    by 4solarisinfo (941037) on Tuesday August 15 2006, @11:41AM (#15911020)
    Due to recent events at NASA, we'd appreciate everyone helping out by recording the stream of the event, and puttting it... well somewhere you can find it later.

  • Warp 1 Mr. Sulu (Score:4, Funny)

    by OakDragon (885217) on Tuesday August 15 2006, @11:42AM (#15911033) Journal

    Cool! Now I can get started on my warp engine!

    Yours, Zephram Cochrane

  • The importance (Score:4, Funny)

    by eebra82 (907996) on Tuesday August 15 2006, @11:44AM (#15911050) Homepage
    So what's the matter, NASA?

  • We like to refer to it as "matter of color."

  • Shouldn't that be "NASA Announces *Announcement Of* Dark Matter Discovery"?

  • Dark Matter (Score:4, Funny)

    by Lost Penguin (636359) on Tuesday August 15 2006, @12:57PM (#15911594) Homepage
    Isn't this what a light bulb absorbs till it's full, and then you must throw it away?

  • Nice visual demonstration that dark matter exists (Score:5, Informative)

    by riptalon (595997) on Tuesday August 15 2006, @01:28PM (#15911877)

    I would assume this is the Bullet Cluster (1E 0657-56) combined X-ray and weak lensing results that Maxim reported [harvard.edu] at the Six Years of Science with Chandra Symposium [harvard.edu] last November. The interesting bit is that in this merging galaxy cluster the hot gas (~ 30%) has collided and been brought to a stop while the dark matter (~ 70%) haloes which are collisionless have passed through each other and are offset from the gas. By plotting the weak lensing image (which shows the total mass) over the X-ray image (which shows the baryons/gas) you can therefore see the existance of dark matter, since the mass is in a totally different place from the gas you can see in the X-ray. This isn't a fundamentally new result but it is a very nice visual demonstration of the existance of dark matter. Rotation curves of galaxies and the temperatures of galaxy clusters had proved it already but with this you don't need to do any maths you can just see it. Page 25 of this 6.5 MB pdf [harvard.edu] is the one you want for the image.

  • Actual NASA Picture of Dark Matter (Score:3, Funny)

    by Kent Simon (760127) on Tuesday August 15 2006, @07:13PM (#15915442) Homepage
    Actual NASA Photograph of their Dark Matter discovery can be found Here [imageshack.us]

    • Not at all (Score:5, Insightful)

      by Moraelin (679338) on Tuesday August 15 2006, @12:22PM (#15911316) Journal
      It's never been about how many planets are enough, and it's not just about Pluto. It's about how you define a planet.

      It's, in a nutshell, about science: attempting to actually classify and understand the universe. Just proclaiming "ok, I hereby do dub Pluto a planet" is ok for everyday life, but a bit too vague for science. It's like you can talk generically about "radiation" in casual conversation or in super-hero comics, but to a scientist that's uselessly vague. A scientist will be more interested in what _kind_ of radiation (i.e., the exact particle), at what energies, etc.

      The same happens in astrophysics. You can't just say "ooh, that's a pretty star", because that doesn't give you much to work with. Is it a planet? An asteroid? A comet? A star? A nova? A white dwarf? What? There are very good reasons to split hairs there, because out of such splitting hairs comes the understanding of what they are and how they work.

      E.g., from the splitting of hairs as to how we classify stars came such categories as "white dwarf." In turn, that let us wonder about how big a white dwarf can be, which gave us the Chandrasekhar limit. In turn that told us that when a star goes over (actually it later it turned out that when it's just right under) that limit, it goes *KABOOM* in a spectacular Type Ia supernova. Since it happens at the exact same point, it tells us that every Type Ia supernova is exactly the same as any other one. Which in turn lets us use them to measure distances and velocities in distant galaxies. And from those came a bunch of other astrophysics stuff.

      _That_ is why for science it's important to worry about such distinction. Sure, you can get through your everyday life without ever worrying about the difference between Pluto and an asteroid, or between a Type Ia and a Type 1b supernova. But for scientists, it's an entirely different situation.

      The informal proclaiming which is what also doesn't scale. When you deal with a whole universe worth of stuff, you have a continuum of things, ranging from individual nuclei all the way to the super-massive black holes in the centre of galaxies. And there are trillions of trillions of them. You can't just go proclaiming for each and every single one of them if it's a planet, an asteroid, or what. You need some rule you can apply there.
        • Congratulations, you have just argued that there are Ten planets. That Ceres should be a planet "because it already has years of tradition in the cultures".

          Ceres was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables for about five decades, until several other asteroids were discovered. You are arguing that Pluto should continue to be listed as a planet for the SOLE reason that it has the same "tradition in the cultures" for about seven decades.

          [Ceres/Pluto] is merely

    • **SPOILER** (Score:5, Informative)

      by drxray (839725) on Tuesday August 15 2006, @12:35PM (#15911401) Homepage
      They're referring to the Bullet Cluster. It's a merging system where a small cluster is passing through a large cluster leaving a shockwave that looks like a bullet's wake, hence the name.
      Dark Matter is collionless, i.e. the DM from the smaller system hasn't been slowed down by the collion and just zooms through. The gas is slowed down. So, the DM and gas are no longer in the same place. We can see the gas in an X-ray telescope (Chandra) and detect the mass by the gravitational lensing effect on the background galaxies.
      This is the first time that this has been shown, and it basically disproves the entire category of theories that DM is an illusional caused by us not understanding the action of gravity at long ranges (MOND).

      Abstract from a conference talk about this. [cosis.net] (PDF)

All trademarks and copyrights on this page are owned by their respective owners. Comments are owned by the Poster. The Rest © 1997-2009 Geeknet, Inc.