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Astronomers Find Star-Less Galaxy 608

Posted by CmdrTaco
from the arrange-a-transfer-from-la dept.
Wohngebaeudeversicherung writes "Astronomers have discovered a galaxy about 50 million lightyears away from earth that appears to be composed entirly of dark matter. This galaxy, dubbed VIRGOHI21 is rotating like a real galaxy, at speeds only explainable through massive amounts of matter, thought no single visible star could be detected."
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Astronomers Find Star-Less Galaxy

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  • by Anonymous Coward on Wednesday February 23, 2005 @12:20PM (#11756041)
    I suggest we donate one of our stars. How about Ben Affleck?
  • by Xpilot (117961) on Wednesday February 23, 2005 @12:21PM (#11756051) Homepage
    ...that I click on "Read More" to find out about matter that's invisible to us and all I get is:

    "Nothing for you to see here. Please move along."

    Brilliant.

  • by MORTAR_COMBAT! (589963) on Wednesday February 23, 2005 @12:21PM (#11756065)
    Astronomers have discovered a galaxy about 50 million darkyears away from Virgo that appears to be composed entirly of light matter. This galaxy, dubbed EARTHHI21 is rotating like a real galaxy, at speeds only explainable through massive amounts of matter, thought no single dark mass could be detected."
  • by ackthpt (218170) * on Wednesday February 23, 2005 @12:22PM (#11756069) Homepage Journal
    "Astronomers have discovered a galaxy about 50 million lightyears away from earth that appears to be composed entirly of dark matter.

    Should't that be 50 million darkyears?

    • by Anonymous Coward on Wednesday February 23, 2005 @12:37PM (#11756261)
      No, the speed of dark is still unknown, but it is expected to be a lot faster than speed of light. Because where ever the light goes, the dark is already there waiting for it.
      • by Anonymous Coward
        While you have a point about the dark already being there waiting for it, once the light gets there the dark never gets out of the way fast enough. So all we can conclude was that dark was pretty fast in the past, but is just sitting around picking its nose these days.
      • As in "How long does it take for a management chain to pass the blame"
  • FYI (Score:5, Informative)

    by Anonymous Coward on Wednesday February 23, 2005 @12:23PM (#11756092)
    It was found 50 million light years away using radio telescopes in Cheshire
    FYI : the radio telescope in Cheshire (that's in North West England), is Jodrell Bank [man.ac.uk]. Which some of you will remember from the following :
    The huge yellow somethings went unnoticed at Goonhilly, they passed over Cape Canaveral without a blip, Woomera and Jodrell Bank looked straight through them -- which was a pity because it was exactly the sort of thing they'd been looking for all these years
  • by funny-jack (741994) on Wednesday February 23, 2005 @12:24PM (#11756104) Homepage
    Maybe the entire galaxy is surrounded by particles of dust from a long-destroyed supercomputer?
  • by JPelorat (5320) * on Wednesday February 23, 2005 @12:24PM (#11756108)
    What the speed of dark is.
  • by Catiline (186878) <akrumbach@gmail.com> on Wednesday February 23, 2005 @12:25PM (#11756123) Homepage Journal
    Aha! It's intelligent life! They must have engineered millions of Dyson Spheres over all the stars of their galaxy!
  • by Angry Toad (314562) on Wednesday February 23, 2005 @12:26PM (#11756129)

    Isn't this what they've been telling us to look for for years now - the entire energy output of a galaxy caught and channelled for use by an intelligence that has spread throughout it's own galaxy?

    /not really serious

    • by Black Parrot (19622) on Wednesday February 23, 2005 @12:49PM (#11756412)


      > Isn't this what they've been telling us to look for for years now - the entire energy output of a galaxy caught and channelled for use by an intelligence that has spread throughout it's own galaxy?

      Such spheres still have to radiate heat, or else the inside of the sphere would become as hot as the star. The Wikipedia article says it would show up as stars emitting radiation with the blackbody spectrum.

      • by WhiplashII (542766) on Wednesday February 23, 2005 @01:07PM (#11756634) Homepage Journal
        This may or may not be true - for example, for my personal Dyson sphere I was displeased by the loss of energy caused by alowing the radiatated energy from the sun to spread over the large volume of my sphere (The effective temperature goes down as you get farther away from the sun), so I made my Dyson's sphere reflective on the inside - focusing the light towards two points on the top and bottom of the sphere. That lead my sphere to emit strongly from the top and bottom, but not at all from the sides.

        It increased thermal conversion effeciency by 50%, making me the envy of all the other Spheriods.

        • by Kehvarl (812337) on Wednesday February 23, 2005 @01:21PM (#11756781)
          If you then made one of those points perfectly reflective and radiated all extra energy out the one point, you could use it as a method of propulsion. You'll that the fastest spheroid around.

  • by 955301 (209856) on Wednesday February 23, 2005 @12:28PM (#11756161) Journal
    My favorite part of the article: Someone thought that circling the invisible galaxy in the picture was a helpful move.

    Personally, I think articles with discoveries this exciting need to be written with more enthusiasm [theonion.com]

    • My favorite part of the article: Someone thought that circling the invisible galaxy in the picture was a helpful move.

      Well, Ok, you may have spotted that galaxy immediatly, but I guess there are many less experienced readers who whould have had a hard time to find it if it hadn't been circled.
  • by ZeeExSixAre (790130) on Wednesday February 23, 2005 @12:31PM (#11756197)
    "Hey Joe... check this out... There isn't a visible star at all!"

    "Um, Bill? The lenscap is still on..."

  • by Anonymous Coward on Wednesday February 23, 2005 @12:33PM (#11756218)
    ...and it doesn't require exotic quarks, leptons, or baryons to work.

    Okay, that's an enormous (and highly unlikely) exaggeration, but I *have* thought of an interesting possibility. A Dyson Sphere surrounding several stars (or in a Type 3 civilization, an entire galaxy) would block visible light - the problem is it would glow in the infrared, so it wouldn't really be dark. Black holes are dark, but they tend to fling stuff around, and matter sucked into them gives off bursts of energy before they disappear.

    The solution: a dark bubble. At the center of our galaxy there is a supermassive black hole, which is (according to some estimates) roughly three million solar masses. A civilization putting a bubble around it would have 1 (earth) gravity a little beyond the orbit of Pluto, perhaps 40-45 A.U. or so. The problem is that you still would need to stick some stars around it to supply energy, and a Klemperer rosette would be pretty noticeable.

    Well, light falling onto a blackhole blue shifts, increasing its energy. Increase the bubble enough (remember, we're talking a civilization that can harness the energy of a galaxy), and the mass of the bubble itself starts to warp space around it. There comes a point where the size of the bubble and the mass that makes it up can be just under the Schwarzschild limit - a bit more massive and it would be a black hole - even without a central singularity. For humans, we'd want a bubble that has a surface gravity equal to earth's, and a blue-shifted energy equal to the average output from our sun.

    As a back-of-the envelope calculation, using v^2=2*g*R, where v is the escape velocity, g is the gravitational attraction at the earth's surface, and R is the radius from the center of mass, and setting v=c (the speed of light) for the maximum size, you get a bubble with a diameter just a bit under a light-year across (354 light days, if I figured correctly). The surface area would be about 3 square light-years, 2.6 x 10^26 square kilometers, or 5.2 x 10^17 times the surface area of the earth. The mass would be equivalent to 1.5 trillion suns - roughly twice the mass of our galaxy. Assuming you use buckytubes as the material of choice, you'd have a shell 7000 kilometers thick of solid buckminsterfullerene.

    Of course, this is the absolute maximum size and mass just before it becomes a black hole, so the actual construct would be a bit smaller and less massive, balancing surface gravity and blue-shifted energy hitting the surface. You'd also want to carve out mountain ranges and oceans for a bit of variety - a galactic Kansas would be kind of boring. For safety reasons, you would have to stick these bubbles in the empty space between galaxies, or just use all of the mass in one large galaxy (you'd have to be careful, though, to keep relativistic rocks from flying at the completed project). You'd have a sky that would look kind of like a slow-moving aurora, perhaps -- infrared would be shifted into visible light, visible stars would have their peak shifted to ultraviolet -- especially since the gravitational warping would slow down time considerably compared to the rest of the galaxy.

    To detect them, you'd have to aim telescopes at the "empty" parts of the sky and see if there was any gravitational lensing. If something was there that was far too massive to be a neutron star but didn't have the characteristics of a supermassive black hole, that could be a sign of it. The largest ones would have the gravitational mass of a large galaxy, so if a supercluster appears to be missing a galaxy's worth of stars that stellar motions demand, it might not be exotic matter but instead bubbles of normal matter from some vast engineering project.

    Of course, it might be too early in the evolution of the universe for a type 3 civilization to appear, or you might not be able to make a buckytube bubble big enough that would also support its own weight, so exotic forms of matter might still be necessary. One thing's for certain, though - a bubble like this would make Ringworld look as spacious as a phone booth.
    • by Anonymous Coward on Wednesday February 23, 2005 @02:11PM (#11757377)
      I have no idea what you are talking about, but I understand I should be impressed. Consequently, I shall memorize random bits from your post and reiterate them over the third bottle of red wine at 2:30 AM.
    • by Rorschach1 (174480) on Wednesday February 23, 2005 @02:21PM (#11757479) Homepage
      You'd also want to carve out mountain ranges and oceans for a bit of variety - a galactic Kansas would be kind of boring.

      Galactic Kansas would, however, be an awesome name for a rock band.

    • Well, light falling onto a blackhole blue shifts, increasing its energy.

      No, light reaching our eyes after travelling near a black hole is redshifted, decreasing its energy. See this Wikipedia article [wikipedia.org] (search for "red-shifted") if you're unable to reason about it yourself: intuitively, a light wave coming at us from the vicinity of a black hole (where the gravity is significantly stronger at the "tail" of the light wave than at the "head" of the light wave) would be stretched out, not squished together.

      • except the OP's pov is effectively inside the black hole, not outside. from inside the black hole, the light falling on top of you would indeed be blueshifted.

        so there's no problem with that plan at all.
    • The maximum size sphere you describe would require 1.6x10^15 jupiter masses of carbon. If every star in our galaxy (200 billion if I remember right) had a solar system, and every solar system had 10 (!) planets the mass of jupiter, and every planet was made of pure carbon, you would need all the carbon of about 80 such galaxies to build that bubble. Then again if there were that many such planets in the universe, it'd be obvious what "dark matter" was.
  • by GillBates0 (664202) on Wednesday February 23, 2005 @12:34PM (#11756221) Homepage Journal
    Twinkle twinkle little star
    How I wonder where you are.
    Lightyears away in VIRGOHI21 so far
    Oh why can't I see you, you naughty naughty star.
  • by njfuzzy (734116) <ian@[ ]-x.com ['ian' in gap]> on Wednesday February 23, 2005 @12:37PM (#11756252) Homepage
    Why is nobody considering that no light is escaping this galaxy because of some sort of hitherto undiscovered crunchy candy shell?

    Seriously, though.... Just because no light gets out doesn't mean no light is produced.

  • by vivin (671928) <vivin DOT paliath AT gmail DOT com> on Wednesday February 23, 2005 @12:37PM (#11756260) Homepage Journal
    Dark Matter is matter that cannot be directly detected through emitted radiation. But you can detect it through its effect on surrounding bodies. The effect is usually gravitational.

    The concept of Dark Matter evolved from the "missing mass problem". You can estimate the amount of mass in a cluster of galaxies based on the motions of other objects around the object in question. When you compare this mass to the mass based on the total brightness (visible mass) of the galaxy, you can find a huge discrepancy. This is the "missing mass".

    Wikipedia [wikipedia.org] provides more information.
    • by Anonymous Coward on Wednesday February 23, 2005 @01:02PM (#11756567)
      ...with my tax return?

      IRS Auditor: We've added up all of the income your employers have reported for you and it is much greater than what is reported on your tax form. How do you explain that.

      Me: While you can usually detect income through tax forms, some types simply don't register. I believe that it is called...dark income.

      IRS Auditor: I believe that it is called...tax evasion.

      Me: gulp...
  • Get the paper here (Score:3, Informative)

    by Anonymous Coward on Wednesday February 23, 2005 @12:40PM (#11756293)
    The preprint [arxiv.org].
  • More detailed info (Score:5, Informative)

    by Agent Orange (34692) <christhom @ g mail.com> on Wednesday February 23, 2005 @12:50PM (#11756421)
    More detailed information can be found in the paper, which has been accepted for publication in a letter to the Astrophysical Journal.

    Find it here [adelaide.edu.au].
  • by balaam's ass (678743) on Wednesday February 23, 2005 @12:54PM (#11756473) Journal
    Oh.
  • by VoidPoint (634537) on Wednesday February 23, 2005 @01:01PM (#11756562)
    Astronomer: Now, you see here, this empty spot on the map? Well, sir, that is the very first Dark Matter galaxy ever discovered.

    Congressman (skeptical): Well, I dunno...I don't really see anything there.

    Astronomer: Oh, one moment...let me circle it for you!

    Congressman: Yes, yes I see it!

    Astronomer: Now I was wondering, Congressman...how much additional funding might we get for this discovery?

    Congressman: Hm. I'm not sure we have additional funds for such an admittedly amazing find. Now, if you had TWO dark matter galaxies, we'd have something to discuss.

    Astronomer (uncapping pen): Funny you should mention that...

  • by Anonymous Coward on Wednesday February 23, 2005 @01:06PM (#11756617)
    Some common objections to dark matter I constantly see whenever the topic comes up on Slashdot:

    Can't dark matter just be brown dwarves or black holes or something? Why do scientists postulate crazy exotic invisible particles?

    Dark matter [wikipedia.org] is postulated to come in two kinds, Massive Compact Halo Objects (MACHOs) and Weakly Interacting Massive Particles (WIMPs). MACHOs are things like brown dwarves, etc.; WIMPs are the new kind of matter. We have already detected some MACHOs through gravitational microlensing experiments (looking for them by how they gravitationally deflect light). But if all the dark matter were MACHOs or something else mundane and baryonic, we would have detected more of them by now. That leaves WIMPs. Also, MACHOs and WIMPs have different physical properties (e.g., they cluster differently, and thus seed the formation of the large-scale galactic clusters we see today in different manners), and an all-MACHO universe doesn't cluster right, though it works out if you let some WIMPs into the mixture.

    Ordinary neutrinos don't do the trick, either; we evidently need some new kind of particle. We don't know what WIMPs are, but some have postulated axions, neutralinos or other supersymmetric particles, WIMPZILLAs, solitons, sterile neutriono (that only interact gravitationally), ...

    Dark matter is unscientific; it can't be tested or falsified.

    Dark matter theories can be tested indirectly by observing the different predictions they make for galactic rotation curves, early-universe structure formation, cosmological expansion, etc. Already such observations have excluded a number of dark matter theories. And there are experiments underway that try to directly detect them, similarly to how we detect neutrinos.

    Dark matter is just epicycles all over again, a fudge factor to preserve a wrong theory of gravity.

    Once upon a time, irregularities were noted in the orbit of Uranus. It could have been postulated that the laws of gravity were wrong. Instead, it was postulated that an unseen bulk of matter was perturbing Uranus's orbit. Eventually, that bulk of matter was seen: the planet Neptune.

    On the other hand, once upon a time, irregularities were noted in the orbit of Mercury. It was postulated that maybe a new planet caused them (Vulcan), but that turned out to be wrong; instead, a new theory of gravity was needed (general relativity).

    The moral: you can attempt to explain away the observations with either dark matter or a new theory of gravity; both are scientifically valid approach. The problem with the latter is that it has proven extraordinarily difficult to produce a modified theory of gravity that is consistent with all observations, whereas there are dark matter theories that appear to do the job. Believe me, scientists don't ignore the possibility of a new theory of gravity any more than they ignore the possibility of a new type of matter; it's just that new theories of gravity don't seem to work as well as new theories of matter in explaining the observations.

    What about MOND?

    MOdified Newtonian Dynamics [umd.edu] is the leading candidate for a non-dark matter alternative, modifying the laws of gravity. (Note that this page is by MOND's inventor, and may be biased.) However, it has had trouble with a number of observational tests; you can search the astro-ph arXiv [arxiv.org] for critiques of MOND. In particular, although it seems to work for galactic rotation curves, it's hard to get it to also work for cosmological expansion and structure formation. It's also very difficult to make it into a theory compatible with observed tests of relativity.

    What about Bekenstein's MOND theory?

    Bekenstein recently proposed a relativistic version of MOND called
  • by Anonymous Coward on Wednesday February 23, 2005 @01:32PM (#11756904)
    Here is the accepted Astrophysical Journal Letter regarding this discovery.

    http://xxx.lanl.gov/abs/astro-ph/0502312 [lanl.gov]

    (Note: Be on guard for confusing astronomical conventions, like measuring almost everything logrithmically with decreasing numbers representing increasing brightnesses.)

    To sum up: Astronomers discovered a large mass of rotating Hydrogen gas towards the Virgo Cluster. From the gas dynamics they were able to estimate the mass of the system, and found it to be comparible to the mass of a galaxy. When they went to look at the optical light given off by stars, they found they couldn't find nearly the amount they should for a normal galaxy, hence the 'star-less galaxy' title.

    Current Cold Dark Matter (CMD) models of galaxy formation predict that these 'star-less' masses of dark matter should exist in the universe. While other candidates have been discovered in the past, this is the only (currently) viable candidate now known. If it holds up to subsequent analysis, it will provide observational support for the CDM formation models.

    A few quick points --
    - Dark matter is simply non-luminous matter (matter that does not emit light at any wavelength).
    - Yes, black holes are a form of dark matter (baryonic).
    - No, this is not an 'anti-matter' galaxy.
    - Current Dark Matter theories lean towards it having a non-baryonic source (i.e. not being made up of 'normal' matter).
  • by GPS Pilot (3683) on Wednesday February 23, 2005 @01:58PM (#11757210)
    TFA says this object is "a mass of hydrogen atoms a hundred million times the mass of the Sun."

    It may be unusual that none of this hydrogen has ignited in a fusion reaction, but that doesn't change the fact that hydrogen atoms are baryonic matter, quite common here on earth. (There are quadrillions of them in my body right now.)

    Later, TFA says "according to cosmological models, dark matter is five times more abundant than the ordinary (baryonic) matter that makes up everything we can see and touch."

    So this object is "dark" in the sense that it doesn't emit visible light, but it's not Dark Matter.

    Or am I missing something here?
  • by bradbury (33372) <(Robert.Bradbury) (at) (gmail.com)> on Wednesday February 23, 2005 @04:05PM (#11758635) Homepage
    Cool... We may have finally observed a collection of Matrioshka Brains [aeiveos.com].
    This would qualify as a Kardashev Type III civilization.

    But don't suggest this to the astronomers or astrophysicists because they are so friggen sure that the universe is *dead* and nothing they observe could be explained by the activity of advanced technological civilizations... They obviously haven't read any of the work by the Lineweaver group pointing out that 75% of the stars in the galactic habitable zone are older (in some cases much older) than the Sun. [Ref: astro-ph/0401024 [arxiv.org]].

    Roll the open source and nanotechnology development efforts forward by a few hundred million years and project what the universe would look like...

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