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Thread: Largest cosmological structure

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    Largest cosmological structure

    What is the largest cosmological structure that can be seen in the universe, where it appears that everything is connected by gravity and rotating around it self or toward something seen or unseen? How big is that structure?
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    It would be a galaxy cluster, I think. Superclusters are generally not bound in the way you mean. So probably RX J1347.5−1145 or something like that, and as for size it would be of order 10Mpc

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    Quote Originally Posted by Shaula View Post
    It would be a galaxy cluster, I think. Superclusters are generally not bound in the way you mean. So probably RX J1347.5−1145 or something like that, and as for size it would be of order 10Mpc
    Are the superclusters not bound because expansion is assumed?
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    Quote Originally Posted by Copernicus View Post
    Are the superclusters not bound because expansion is assumed?
    A quick hunt and here is a paper on how they test bound vs not bound: https://arxiv.org/pdf/1404.1308.pdf
    It also has a section of the Shapely Supercluster as bound and hence the largest known bound structure.

    They don't 'assume' expansion - they use the observed redshift differences as indicators of the difference in velocity between the components of the clusters and use that to bootstrap a velocity dispersion distribution. Then they simulate what happens over time using the estimated or observed mass distributions of the target.

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    The most recent simulation:
    https://www.space.com/most-detailed-...imulation.html

    Could filaments (which contain superclusters) be considered structures?

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    Quote Originally Posted by publiusr View Post
    Could filaments (which contain superclusters) be considered structures?
    They are structures but not gravitationally bound structures.

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    Quote Originally Posted by Shaula View Post
    They are structures but not gravitationally bound structures.
    Thank you.
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

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    Have you considered GRGs (giant radio galaxies)?

    WP is of some help; briefly, the largest are ~5 Mpc end-to-end, though most of the largest are not continuous (at least in the radio to the sensitivity of contemporary observatories).

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    Quote Originally Posted by Jean Tate View Post
    Have you considered GRGs (giant radio galaxies)?

    WP is of some help; briefly, the largest are ~5 Mpc end-to-end, though most of the largest are not continuous (at least in the radio to the sensitivity of contemporary observatories).
    This confuses me. I thought we were talking of structures that were many galaxies in size.
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    Quote Originally Posted by Copernicus View Post
    This confuses me. I thought we were talking of structures that were many galaxies in size.
    The/your OP is ambiguous; to me quite unclear.

    GRGs are, or can be, far bigger than any individual galaxy. Some may extend beyond the boundaries of the galaxy cluster they originate in.

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    Quote Originally Posted by Jean Tate View Post
    The/your OP is ambiguous; to me quite unclear.

    GRGs are, or can be, far bigger than any individual galaxy. Some may extend beyond the boundaries of the galaxy cluster they originate in.
    Thanks! Sometimes I have difficulty figuring what to ask, sometimes I leave it more up to interpretation to see where the question can go. I am really wondering if some gravitationally bound structures are so big, that they could obscure anything looking like a center of the universe. If there was a center to the universe.
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    Quote Originally Posted by Copernicus View Post
    Thanks! Sometimes I have difficulty figuring what to ask, sometimes I leave it more up to interpretation to see where the question can go. I am really wondering if some gravitationally bound structures are so big, that they could obscure anything looking like a center of the universe. If there was a center to the universe.
    What do you mean by "looking like a center of the universd"? Could you give some technical details?

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    Quote Originally Posted by Hornblower View Post
    What do you mean by "looking like a center of the universd"? Could you give some technical details?
    I was wondering if there was a possibility of a 500 million light year, or so, gravitationally bound structure. It was just more or less a curiosity thing.
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    Quote Originally Posted by Copernicus View Post
    I was wondering if there was a possibility of a 500 million light year, or so, gravitationally bound structure. It was just more or less a curiosity thing.
    The Laniakea Supercluster is the size you're looking for, but I believe that current thought is that it appears to not be gravitationally bound. I don't know how solid that conclusion is (I believe that Laniakea was initially thought to be bound), so I suppose it's at least in the realm of possibility that further study would change that. I don't think there's any a priori reason why such a structure could not exist, and the smaller superclusters that make up Laniakea do seem to be gravitationally bound.
    Last edited by Grey; 2019-Dec-05 at 02:42 PM. Reason: Fixed link.
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    As publiusr and shaula implied above, it is possible for for there to be something that is not gravitationally bound to be called a structure. It would need to have been something the boundaries and materials of which were influenced by anisotropies and forces in the early universe. Perhaps jets, or collapsing filaments and sheets, or non-uniform ending of inflation, or some other effect. We can look at and identify structures like Laniakea, but until we see a statistically large sample of them we might be grasping at straws to guess wheat formed them. This puts them at the wild, fun, speculative edge of cosmology.
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    Quote Originally Posted by antoniseb View Post
    Perhaps jets, or collapsing filaments and sheets, or non-uniform ending of inflation, or some other effect at the wild, fun, speculative edge of cosmology.
    In terms of the longest "solid?" structure--perhaps cosmic strings?
    http://www.space.com/cosmic-strings-...spacetime.html

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    Quote Originally Posted by publiusr View Post
    In terms of the longest "solid?" structure--perhaps cosmic strings?
    http://www.space.com/cosmic-strings-...spacetime.html
    So amazing.
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

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