• mpc755
    Ghostly galaxy without dark matter stuns astronomers

    The galaxy is "missing dark matter" because it is too diffuse to displace the dark matter to such an extent that it causes the light to lense around it.

    Dark matter fills 'empty' space, strongly interacts with visible matter and is displaced by visible matter.

    It's not that there is no dark matter connected to and neighboring the visible matter. It's that the galaxy is not well defined enough to displace the dark matter to such an extent that it forms a 'halo' around the galaxy.

    A galaxy's halo is not a clump of dark matter traveling with the galaxy. A galaxy's halo is the state of displacement of the dark matter.
  • TimeLine
    Yeah, I saw this and was pretty astonished because it changes the idea of how the universe and galaxies are formed. Galaxies contain characteristics such as thin and thick disk, bar(s), galactic nucleus etc, and in this instance there appears luminous (stellar) halo without any dark matter.

    Going on what you are saying about DM, galaxies lens the light between our observations here on earth and the cosmic microwave background (CMB) and provides us with a greater understanding of larger scale structures as well as dark matter as the latter must exist to ensure that galaxies themselves to do collapse or evaporate and thus hold form. The best way to describe dark matter is an unknown, non-luminous material that we cannot directly see. Einstein’ theory elucidates that matter and energy are two different states, therefore dark energy and dark matter can also be treated with the same separateness, although our understanding of either phenomenon remains problematic. The temperature fluctuations in the CMB have enabled scientists to measure the existence of cold dark matter (CDM) where measurements of the brightness and intensity of the radiation field is explained using temperature. So Dark Matter must exist to hold galaxies together and for the perturbations in the CMB, but Dark Energy is the source of the cosmological constant or the energy that enables both expansion and acceleration of the early universe.

    There are different type of DM as mentioned, including Hot Dark Matter – which differs from Cold Dark Matter because the former’ speed and movement are caused by neutrino particles and are faster or more energetic.Hot dark matter would not have permitted larger scale structures to have adequately formed because of the high speeds. There is also Warm Dark Matter that no one really cares about, nevertheless it contains inert or sterile neutrinos as well as properties called gravitinos and that the theory is the medium between hot and cold matter that would ultimately balance the theoretical combination of general relativity with the theory of supergravity.

    A Dark Matter Halo was observed when the outer edge of a spiral galaxy contained matter that moved at the similar speeds to the matter within the inner part of the galaxy, which contradicts gravitational laws since the outer edge should in fact be moving slower and thus this is explained in the form of dark matter, matter that does not directly need light to interact. When you look at elliptical galaxies, DM halos are more dense in the centre of the galaxy but this suggests that it does not envelop the galaxy despite dark matter halos being the material that envelops galaxies and galaxy clusters to balance the gravitational pull that would otherwise cause an evaporation or collapse. Dark matter halos are apparently formed through gravitational instability. According to inflationary cosmology, inflation is pushing Ω to 1 with Ω being the mass density divided by critical mass density, thus the asymptotic curvature of the universe is being exponentially flattened. During this process of expansion, a small volume of dark matter expands with the universe as it reaches critical mass density, before it turns and collapses to form "viralized dark matter halos" and continues to grow either by "accreting material... or merging with other halos."

    There are three types of matter, namely that of dark matter, ordinary matter (baryons) and photons or “light” and as the early universe expands and cools as hydrogen is formed through ‘recombination’ which is where charged electrons and protons bound together to form hydrogen atoms. The CMB is during this period of recombination had photons separate and no longer bound by matter, the strength of these oscillations or perturbations is measured and the height of these oscillations measure dark matter and the smaller or more compressed, the more dark matter over regular matter. In this instance - as in with this galaxy - there is more regular matter.

    So this changes shit.
  • Jonathan AB

    There is so much sophistry being said about 'dark matter'.
    There is nothing complex about it at all.
    The amount of matter in a galaxy used to be estimated by the amount of light
    the galaxy emitted based on quite crude statistics. Then, because of gravitational
    lensing, it was realized that there was just more matter than the stats had previously
    suggested. Its nothing more than that. To somebody in another galaxy, objects
    like the Earth would be effectively 'dark matter' because they do not emit light.
  • Janus
    To somebody in another galaxy, objects
    like the Earth would be effectively 'dark matter' because they do not emit light.
    Jonathan AB

    That would seem to be a wrong conclusion, insofar as objects such as the Earth reflect light.
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