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Computer Model Points To the Missing Matter

Posted by kdawson on from the on-a-whim dept.

eldavojohn writes "There exists a little-known problem of missing regular matter that has perhaps been overshadowed by the mysteries of dark matter and dark energy. Computer models show that there should be about 40% more regular matter than we see... so where is it? From the article: 'The study indicated a significant portion of the gas is in the filaments — which connect galaxy clusters — hidden from direct observation in enormous gas clouds in intergalactic space known as the Warm-Hot Intergalactic Medium, or WHIM, said CU-Boulder Professor Jack Burns... The team performed one of the largest cosmological supercomputer simulations ever, cramming 2.5 percent of the visible universe inside a computer to model a region more than 1.5 billion light-years across.' This hypothesis will be investigated and hopefully proved/disproved when telescopes are completed in Chile and the Antarctic. The paper will be up for review in this week's edition of the the Astrophysical Journal."

5 of 97 comments (clear)

  1. Not Dark Matter by iamlucky13 · · Score: 5, Informative

    Since I'm sure the question will be asked, no this missing mass is not dark matter, as both the summary and the article are clear to emphasize. I wanted to repeat that. The primary evidence for dark matter is the galactic rotation curves. The article is talking about gaseous normal matter that we believe exists, but hasn't spotted yet. This missing gaseous matter is nowhere near sufficient in mass to explain the gravitational effect of dark matter and is being looked for on a scale larger than galaxies. The missing mass is an estimate 2% of the mass of the universe, whereas dark matter is an estimate 25%.

    Also, I though it interesting that the is a very interesting rendition of the nearby universe. It's not related to the article, but it does show the filamentary structure the article talks about.

    1. Re:Not Dark Matter by explosivejared · · Score: 2, Informative

      Right on, the matter the article discusses matter that should be there as pointed out in the Dirac equation. The universe should, based on theory, be made up of a certain percentage of baryons (three quark particles).

      --
      I got a catholic block.
    2. Re:Not Dark Matter by fnordboy · · Score: 2, Informative

      Ok, fair point - there are a lot of little, dense things like brown dwarfs and planets that we can't currently observe. However, these can only be a tiny component of the "dark" stuff that we don't see. If brown dwarfs or planets comprised a significant chunk of the dark matter, it would be detected by gravitational microlensing events, and those observations suggest that dense baryonic objects (such as stars, brown dwarves, etc.) aren't a big (which is to say, dynamically important) component of the galactic halo.

      Also, with respect to dust, it's actually quite easy to detect it in the interstellar medium, in both emission and absorption. It doesn't ALWAYS emit radiation, and doesn't do it spontaneously, but when dust is bombarded by light from nearby stars, it tends to re-emit in the infrared and radio. So it's incredibly easy to detect it in both of those bands, and use it to learn things about galaxies. It blocks optical light, of course, so you can see it in nearby (and not so nearby) gas-rich galaxies.

      I see by the link below your name that you're from Berkeley, or at least probably have some berkeley ties. You should go talk to Chris McKee in the astronomy department if you think dust is more of a pain than it's worth - he'll set you straight!

    3. Re:Not Dark Matter by iamlucky13 · · Score: 2, Informative

      Sorry if I'm misreading your post, but what I was saying in my original post is that the matter the article is dealing with is a completely separate issue in astronomy from dark matter. You seem to be interpreting it as saying dark matter is probably actually normal matter. I won't get into that debate here but just want to clarify that this is not what either the paper or I was suggesting.

      Dark matter was detected gravitationally and generally believed to be non-baryonic. The matter in question has not been detected at all, but is thought to exist based on the current models of how the universe was formed. Dark matter appears to make up 25% of the mass/energy in the universe. The matter the article discusses in only about 2%.

      Also, from my interpretation of the article and prior reading, it shouldn't be dust, but simply vast clouds of mostly hydrogen and some helium gas. This stuff would reside in the huge volumes of space between the galaxies and would never have achieved sufficient densities to collapse into stars where it could be fused into the heavier atoms necessary to form space dust. At the distances, densities, and temperatures involved, it would be undetectable with our current technology.

      And of course, there is free gas and dust that we are able to see in the Milky Way and neighboring galaxies, but this also is a separate issue.

  2. Re:missing matter != dark matter? by Bryan+K.+Feir · · Score: 2, Informative

    There's this story from a while back, which pointed to at least one case where the non-baryonic dark matter reacted differently from the baryonic matter. There was a galactic collision, and the non-baryonic matter sort of coasted on while much of the baryonic gas slammed together in the middle. Since non-baryonic dark matter reacts only to gravity, there are ways to distinguish between the two...