Astrophysicists find Big Ring of Galaxies that Should Not Exist

[This is a transcript with links to references.]

A group of astrophysicists have found another megastructure in the universe. They’ve called it the “Big Ring” and it’s a whopping 1 point 3 billion light-years in diameter. The thing isn’t just huge, it’s also a huge problem for our understanding of how the universe works. Because it shouldn’t exist. I’m somewhat afraid that all other astrophysicists will try to ignore this, which is why I thought we should talk about it. Let’s have a look.

The Big Ring is an unusual accumulation of matter about 9 point 2 billion light-years away from Earth, that’s approximately the same distance as Elon Musk’s brain is from mine. The Big Ring is located near the handle of the Big Dipper, or near the tail of the Big Bear if you’re German, and about the same size as the ladle or the bear, or the wagon or whatever you call the thing.

Don’t worry too much about where it is, because you can’t see it anyway. It’s incredibly faint.

The astronomers found the Big Ring near another mega structure called the “Giant Arc” using data from the Sloan Digital Sky Survey. They did this by looking at bright objects called “quasars” behind the giant structures and then calculating how much of the quasar light was absorbed. This allowed them to figure out how much mass is in-between and what they found is this Big Ring.

For all I know the discovery hasn’t yet been published, but it was announced at a meeting of the American Astronomical Society last week, accompanied by a press release from the University of Central Lancashire in the UK. But I assume it will soon be published.

This discovery is problematic because it conflicts with one of physicists’ most cherished assumptions, the cosmological principle. The cosmological principle is the idea that the universe looks on average the same everywhere. There are no special places, basically.

You might object that the universe arguably does not look the same everywhere. Unless you’re very acrobatic, there’s more matter under your feet than above your head and more matter in the Milky way than in intergalactic space, and so on. Physicists have noticed that too, so the cosmological principle more precisely says that matter in the universe is equally distributed when you average over sufficiently large distances.

But how large is sufficiently large? That depends on your theory for how the universe expands. So the thing is that if you assume that the cosmological principle is valid within a particular theory, then you can calculate the distance at which averages should all be equal.

The thing is now that in the currently most widely accepted model for the universe, known as the concordance model or LambdaCDM, the distance at which the cosmological principle should be a good approximation to the real distribution of matter is about 1 billion light years or so. The Big Ring is larger than that. And that’s the problem.

It's not even the first such megastructure that astrophysicists have found. Already in nineteen-ninety-one, they found a group of thirty-four Quasars, about the same distance as the big ring that extends over two Billion Light-years. It’s called the Clowes-Campusano-Quasar group. Since 2003 astrophysicists also know the „great wall“,  that’s a collection of galaxies about a billion light years away from us that extends over 1 point 5 billion light years. That too, is larger than it should be. . Then there’s the „Huge quasar group“ which spans four Billion light-years , the Giant Arc and now also the Big Ring.

If our current theory of the universe was correct, these structures shouldn’t exist.  It can happen that such accumulations of matter appear coincidentally. That’s because the original distribution of matter in the universe was random. But you can calculate the probability for that to happen. The Big Ring alone is an outlier at 5 point 2 sigma, meaning it has a probability of less than one in 3 million to have appeared by chance. And that doesn’t factor in all the other big structures.

What does that mean?  It means that the evidence is mounting that something doesn’t properly work without current theories for the universe. We either need a new theory, or the cosmological principle has to go, which means that we would need a new model within the same theory. Or both.

I’ve heard people say that it would be possible to explain these features with cosmic strings or with Penrose’s cyclic cosmology, and that might be so, though I haven’t seen calculation. But even if that was possible it’d be kind of like shooting nuclear missiles at pigeons. First thing that astrophysicists will try is to weaken the cosmological principle.

Whatever’s up, these are exciting times for cosmology, and I’ll keep you up to date so stay tuned.