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Waspie_Dwarf

Hubble Focuses on "the Great Attractor"

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Hubble Focuses on "the Great Attractor"

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A busy patch of space has been captured in this image from the NASA/ESA Hubble Space Telescope. Scattered with many nearby stars, the field also has numerous galaxies in the background.

Located on the border of Triangulum Australe (The Southern Triangle) and Norma (The Carpenter’s Square), this field covers part of the Norma Cluster (Abell 3627) as well as a dense area of our own galaxy, the Milky Way.

The Norma Cluster is the closest massive galaxy cluster to the Milky Way, and lies about 220 million light-years away. The enormous mass concentrated here, and the consequent gravitational attraction, mean that this region of space is known to astronomers as the Great Attractor, and it dominates our region of the Universe.

The largest galaxy visible in this image is ESO 137-002, a spiral galaxy seen edge on. In this image from Hubble, we see large regions of dust across the galaxy’s bulge. What we do not see here is the tail of glowing X-rays that has been observed extending out of the galaxy — but which is invisible to an optical telescope like Hubble.

Observing the Great Attractor is difficult at optical wavelengths. The plane of the Milky Way — responsible for the numerous bright stars in this image — both outshines (with stars) and obscures (with dust) many of the objects behind it. There are some tricks for seeing through this — infrared or radio observations, for instance — but the region behind the center of the Milky Way, where the dust is thickest, remains an almost complete mystery to astronomers.

This image consists of exposures in blue and infrared light taken by Hubble’s Advanced Camera for Surveys.

ESA/Hubble & NASA

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This is an incredible image...

It's indescribable how small I feel right now.

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This"Great Attractor" is amazing.... wonder if its a SUPER SUPER SUPER massive black hole, Waspie what is your thoughts on this?

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If it's real and not a consequence of some measurement bias, then it would be outside the visible universe (beyond the threshold where space is expanding from us faster than light) and would almost certainly be a super-galaxy cluster.

This would mean that the homogeneity of the universe at really large volumes that we have always assumed is not correct, with a variety of cosmological consequences. The recent discovery of a large cluster of quasars also seems to put that homogeneity in some question, although on a smaller scale.

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If it's real and not a consequence of some measurement bias, then it would be outside the visible universe (beyond the threshold where space is expanding from us faster than light) and would almost certainly be a super-galaxy cluster.

This would mean that the homogeneity of the universe at really large volumes that we have always assumed is not correct, with a variety of cosmological consequences. The recent discovery of a large cluster of quasars also seems to put that homogeneity in some question, although on a smaller scale.

I don't understand what you meant by that Frank... I thought the Universe was roughly 14 billion LYs in radius... This cluster is "only" 220 million LYs away, so how could it be outside the visible universe?... Please explain if you have the time (please use small(ish) words so my brain won't overload :) )

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I don't understand what you meant by that Frank... I thought the Universe was roughly 14 billion LYs in radius... This cluster is "only" 220 million LYs away, so how could it be outside the visible universe?... Please explain if you have the time (please use small(ish) words so my brain won't overload :) )

Talking here about two different things, both of which seem to indicate that previous ideas about the size range at which homogeneity takes over may be too small. Actually I don't think either is going to do that, but the future will tell.

The "great attractor" is not the cluster of quasars recently identified. It is something beyond the range of what we are able to see, so all we can see is its gravitational effect on galaxies in that part of the sky. I forget off the top what the diameter of the "visible universe" is but it is something larger than the age of the universe as the universe has been expanding all that time. Beyond that we have no idea how far the universe may go on, if not forever, but we will never be able to know because its out of our range -- the light from such places will never reach us. Remember that light takes a finite time to get from one place to another, so that as we look out in space we also look back in time, and can never see beyond the Big Bang.

The reason I mentioned the cluster is that it also is bigger than what had up to now been presumed the maximum size of a single object. So it, too, in a much smaller way, could bring the homogeneity idea (aka "Copernican Principle" into question. Actually I doubt any such thing.

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The "great attractor" is not the cluster of quasars recently identified.

Isn't the ``great attractor'' the supergalaxy cluster (as indicated in the wiki) and what you are referring to is the (somewhat disputed) phenomenon of ``bulk flow'' or ``dark flow'' (see here or here)?

I'm not arguing with your points about how ``bulk flow'' could refute the idea of large-scale homogeneity, only that the post here refers to studying the supergalaxy cluster specifically, not the wide-scale motion of galaxies.

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Stephen Baxter, a British sci-fi writer, wrote a book series (or a series of books linked together because they take place in the same universe) called the Xeelee Sequence. In it, the Great Attractor is a massive constriction made by the Xeelee to escape the current unverse since their enemies, the Photino Birds (creatures made of dark matter) were speeding up the heat death of the universe. Cool book series. Cooler that the Hubble is finally taking a peek.

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If it's real and not a consequence of some measurement bias, then it would be outside the visible universe (beyond the threshold where space is expanding from us faster than light) and would almost certainly be a super-galaxy cluster.

I'm not sure how you have come to this conclusion. If it is travelling away faster than light then so is it's gravitational affects. Edited by Rlyeh
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I'm not sure how you have come to this conclusion. If it is travelling away faster than light then so is it's gravitational affects.

The great attractor is beyond our threshold, so we are not being attracted to it; what we see are the effects on galaxies on that end of our universe that are closer to it. For these objects the great attractor is not on the other side of their threshold.

Good question though.

Edited by Frank Merton

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The great attractor is beyond our threshold, so we are not being attracted to it; what we see are the effects on galaxies on that end of our universe that are closer to it. For these objects the great attractor is not on the other side of their threshold.

Not really. For us to see something it must be in our ``causal past'', i.e. our light cone. If an object is in our causal past, then the causal past of that object is also in our causal past.

So if a very distant (but observable!) galaxy is being affected by a non-superluminal event, the source of that event should also be observable.

The great attractor you are referring to may not be visible (i.e. may not appear in visible light based telescopes), but it should still be observable (i.e. via neutrinos, or perhaps gravitational waves, or something).

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Not really. For us to see something it must be in our ``causal past'', i.e. our light cone. If an object is in our causal past, then the causal past of that object is also in our causal past.

So if a very distant (but observable!) galaxy is being affected by a non-superluminal event, the source of that event should also be observable.

The great attractor you are referring to may not be visible (i.e. may not appear in visible light based telescopes), but it should still be observable (i.e. via neutrinos, or perhaps gravitational waves, or something).

What you say is possible but I don't think likely. I think the most likely thing is that it will all prove to have been an illusion; the second most likely is that there exists a super-cluster of galaxies out of our light cone (a term I had not used as being technical) but not outside the light cone of the effected galaxies. We are not seeing the big attractor, we are only seeing its effects on galaxies that are still in our light cone and that have the attractor in their light cone.

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...the second most likely is that there exists a super-cluster of galaxies out of our light cone (a term I had not used as being technical) but not outside the light cone of the effected galaxies. We are not seeing the big attractor, we are only seeing its effects on galaxies that are still in our light cone and that have the attractor in their light cone.

That is not possible. The (past) light cone of every object inside our (past) light cone is also in our past light cone.

If we can see and object, and that object is being affected by a luminal or subluminal force or field, then we can also see the source of that force or field.

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That is not possible. The (past) light cone of every object inside our (past) light cone is also in our past light cone.

If we can see and object, and that object is being affected by a luminal or subluminal force or field, then we can also see the source of that force or field.

Well, it is possible, but you will forgive me if I decline to get into this with you as I begin to doubt you understand the idea of something being outside the threshold of our available universe.

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This whole disussion seems to revolve around the phenomena predicted by Special Relativity. In particular reference to Gravitational Waves (completely without any scientific basis), Neutrino propogation (completely misunderstood), and reference to Superluminal Events (un testable), suggests to me nothing more than a Thought Experiment, and therefore not determinable.

Frank Merton:you seem to have given up on any further explanation that falls outside your own special interest

Edited by keithisco
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All I will say, and if you insist I will let you have the last word as this is all I intend to post here, is that while at first I thought your questions were of genuine scientific interest, I now suspect instead you have an ax you are grinding, and I am not interested.

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