Not even galaxies, but massive galaxy clusters. The spatial smoothing used for the ring image is a 2D gaussian with an equivalent width of 11 Mpc, or 37 million light years, big enough to contain all the 2000 galaxies in the nearby Virgo cluster with room to spare. That's for each point in the ring (and that's why they all look so nice and round. These astronomers are playing a statistical game where a pixel combines information from trillions of stars) It's called the Big Ring for a reason. Our own Laniakea supercluster [1], whose dimensions are bigger than anyone imagined up to a few years ago, can be tiled inside the ring several times over.
At that spatial scale, the Universe is supposed to be homogeneous. We do not have plausible mechanisms to generate structures on such a massive scale.
Regarding your analogy with a constellation, yes you can always draw arbitrary squares and triangles among bright stars. But if you had 20+ stars arranged in a circle like that ring, no one would think it was a chance projection, you would demand a physical explanation. We do in fact have such a ring around us: the Gould Belt [2], made of young stars all around the Sun. It is difficult to recognize precisely because we are inside it, and its stars are spread all around the sky. And, of course, some kind of physical explanation is invoked for this ring as well.
Moreover we do know it's an actual ring, and not some chance alignment, because we can derive the distance of each point from its redshift, and it turns out that they are all quite similar.
The authors spend quite a few pages describing the 3D ring structure, showing that it's a ring only when seen from our direction, and how it would appear like an arc or a strange shape from other viewpoints. It would still be a kind of overdense structure, but maybe more difficult to recognize.
BTW the mechanism used to detect the ring is quite clever: it's not a sky image, but rather an absorption map: thousands of background quasars provide a sort of uniform illumination, and they look where this light is removed by clumps of matter.
> Anyway, given the number of galaxies in the ring, being at different distances but their projections just happening to form a rough circle would be even more astonishing than the galaxies in fact sharing a causal history due to some unknown early-universe mechanism.
I don't understand what you mean by this. Why would it be "more astonishing" than an actual causal connection? Surely astronomers are more interested in causal connections than observational coincidences?
To illustrate: the stars making up the constellation of Norma [1] form a rough square when seen from earth, but as their distances from Earth vary greatly this is just an illusion caused by Earth's relative orientation to them. Given the Copernican principle (which I accept is not a physical law) I'm struggling to see why a group of galaxies that form a circle only when seen from "near" earth [2] are actually cosmologically significant.
I accept that the ring contains more than four galaxies, and this makes the ring more statistically significant than a square of galaxies. But it still implies a privileged viewpoint in order for it to be actually significant. I still have the gut feeling that this potential significance is more than offset by the enormously greater observational scale.
tl/dr: why is this more than just naming a new constellation?
(Just to re-iterate: I'm interested in understanding the errors in my mental model - and I'm not trying to poke holes in the work of scientists more qualified them me.)
Galaxies. And determining the approx relative distance of distant galaxies is in fact easy thanks to cosmological redshift (the z values the article refers to). Anyway, given the number of galaxies in the ring, being at different distances but their projections just happening to form a rough circle would be even more astonishing than the galaxies in fact sharing a causal history due to some unknown early-universe mechanism.
The article also mentions that either the circle or the arc in itself could be just a statistical coincidence – as long as we dok’t find more such structures – but the existence of both the circle and the arc, in the same part of the sky, is highly suspicious.
I don't think a ring of galaxies is going to look very different from anyplace within the solar system. Anyway I think moralestapia's point is that the circle might not be centered on us, so the redshift of the galaxies would not be the same. We could still determine that a circle exists by plotting the galaxies in 3D.
They're saying the Big Ring is a neighbor not of earth, but of the "giant arc of galaxies" which "appears in the same region of sky at the same distance from Earth as the Big Ring".
There is also the multiple-endpoints principle to think about. The likelihood of this particular set of galaxies forming a ring is very low. The chance of some set of galaxies among all the billions in the sky doing this is much higher.
Then we notice and cherry-pick only the one interesting data point, we never notice all the mundane ones.
It's always difficult to tell if a popular-science article is really describing something unusual or if it's using selective perception to create the illusion of one. (I have no idea in this case.)
> look behind it, and there are whole edge-on spiral galaxies in the distance. Not stars. Galaxies.
just to add to the awe of that, pretty much every "dot" in one of these images is going to be another galaxy. individual stars from within the Milky Way will have diffraction spikes and very obvious as a single item.
Looking at the angular size of the region in question, it surely would have to be that they’re equidistant from us in order to be at all interesting. There should be innumerable galaxies in and around the ring, from our perspective.
The artist impression in the article is heavily misleading IMHO. The actual "ring" is much more jagged and looks very similar to all the nearby so called "filaments" they labeled. I'm not sure if it's crossing the threshold from constellation-ism to real astronomy. Download the arXiv paper and see for yourself.
> This slice of the vast universe covers a patch of sky approximately the size of a grain of sand held at arm’s length by someone on the ground.
> The image shows the galaxy cluster SMACS 0723 as it appeared 4.6 billion years ago. The combined mass of this galaxy cluster acts as a gravitational lens, magnifying much more distant galaxies behind it
The vastness of it all is mind numbing, it gives me mixed feelings of awe, humility, and dread.
1. There are three bright blobs on the image; I assume they are the same object, behind the BH. What are they/is it? They said the image was averaged; so presumably whatever the blobs are wasn't moving?
2. Is it correct that the rest of the ring, ignoring the three blobs, is the far side of the accretion disk? Why can't I see this side of the accretion disk?
3. According to the article, at least one submillimeter telescope was important. But submillimeter is infrared, isn't it? I thought infrared was blocked by dust, and if there's one thing there's a lot of at the centre of the galaxy, it's dust?
[Edit] Questions 1 and two were prompted by this remark in the article:
"The new view captures light bent by the powerful gravity of the black hole"
The only "light" I can see is a ring with blobs in it; that's why I suppose the ring in the image is not the accretion disk, at least, not as viewed from the pole. Most other commenters here assume (or know) that it is the accretion disk, and we are looking at a pole.
But if that is indeed the accretion disk, then that isn't light that's been bent by the gravity of the black hole.
Perhaps the explanation is that many other commenters haven't actually read the article.
Or a weird lens effect. Gravitational lensing has a logarithmic effect doesn’t it? Theres the old joke about fitting a line to log scale data with a fat enough pen. These galaxies aren’t perfectly circular to each other.
I think the fact that the arc has a similar focus to the ring is going to turn out to be something.
Very cool that there’s a second ring galaxy you can see by looking through the first one! And here I was not even knowing ring galaxies existed until today!
I would have sworn I've seen an animation implying that at sufficient magnification the whole thing loops around to galactic superclusters. Non-intuitive, to be sure...
> This galaxy is so distant that it would have been invisible without the gravitational lensing effects of a large galaxy cluster called Abell 1689, located nearly 2.2 billion light years away in the constellation Virgo.
Not entirely sure if it applies to this two cases "Big Ring" and "Giant Arc", here, but other large "structures" have been found in the past and this paper "Seeing patterns in noise: gigaparsec-scale "structures" that do not violate homogeneity (2013)[0] addresses the possible randomness:
>In general when using an algorithmic approach to identify clusters of points in a distribution, one must employ some criterion in order to decide whether the results obtained correspond to ‘real’ structures in the Universe, or are merely artefacts of the algorithm. One possible criterion is theoretical: if there is a good reason to believe that the points in the cluster are in fact gravitationally bound, for instance, or if its properties match those of structures that are expected to exist in the real Universe, it may be regarded as real. Alternatively, to assess unusual clusters which do not conform to theoretical expectation, the relevant criterion is whether they are unlikely to have arisen purely from noise.
Since the linkage length used to identify the Huge-LQG is so large, there is no reason I know of to believe that it forms a gravitationally bound structure. Certainly no real structures of such size are expected in the standard cosmology. On the other hand, when using this linkage length the clustering algorithm often finds such extended structures even in pure Poisson noise. It therefore appears that the Huge-LQG fails to satisfy either criterion, and so its interpretation as a ‘structure’ is highly questionable. This conclusion is even more applicable to the other slightly smaller quasar groups whose existence has also been claimed.
This is more like a ring galaxy, formation models of which usually involve a fast, dense galaxy smashing through the center of another, leaving behind a compact core and a turbulent, distant ring of active star formation.
And alas, this phenomenon does not include any actual donuts... although if there's enough money at the end of the month, your next astronomy department colloquium might feature some, if you arrive early.
As sega_sai said, there are patterns in the way the galaxies are distributed. Around every galaxy, there is a ring where there is a greater chance of finding another galaxy. It's called the Baryon Acoustic Oscillation, and measuring it is the reason we took these images in the first place! Measuring the size of that ring at different times in the past will hopefully help us figure out how dark energy behaves. See desi.lbl.gov, eg.
Not even galaxies, but massive galaxy clusters. The spatial smoothing used for the ring image is a 2D gaussian with an equivalent width of 11 Mpc, or 37 million light years, big enough to contain all the 2000 galaxies in the nearby Virgo cluster with room to spare. That's for each point in the ring (and that's why they all look so nice and round. These astronomers are playing a statistical game where a pixel combines information from trillions of stars) It's called the Big Ring for a reason. Our own Laniakea supercluster [1], whose dimensions are bigger than anyone imagined up to a few years ago, can be tiled inside the ring several times over.
At that spatial scale, the Universe is supposed to be homogeneous. We do not have plausible mechanisms to generate structures on such a massive scale.
Regarding your analogy with a constellation, yes you can always draw arbitrary squares and triangles among bright stars. But if you had 20+ stars arranged in a circle like that ring, no one would think it was a chance projection, you would demand a physical explanation. We do in fact have such a ring around us: the Gould Belt [2], made of young stars all around the Sun. It is difficult to recognize precisely because we are inside it, and its stars are spread all around the sky. And, of course, some kind of physical explanation is invoked for this ring as well.
Moreover we do know it's an actual ring, and not some chance alignment, because we can derive the distance of each point from its redshift, and it turns out that they are all quite similar. The authors spend quite a few pages describing the 3D ring structure, showing that it's a ring only when seen from our direction, and how it would appear like an arc or a strange shape from other viewpoints. It would still be a kind of overdense structure, but maybe more difficult to recognize.
BTW the mechanism used to detect the ring is quite clever: it's not a sky image, but rather an absorption map: thousands of background quasars provide a sort of uniform illumination, and they look where this light is removed by clumps of matter.
[1] https://en.wikipedia.org/wiki/Laniakea_Supercluster
[2] https://en.wikipedia.org/wiki/Gould_Belt
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