One of the bedrock tenants of cosmology is our universe being smooth. In other words, it pretty much is the same in terms of matter distribution and density everywhere when observed on a large scale (billions of light years). Of course, on smaller scales our universe looks lumpy but big picture it is supposed to be pretty much a Vitamix puree.
Enter the Sloan Digital Sky Survey, enabled by generous help from the Alfred P. Sloan Foundation. With operations commencing in 2000, the Sloan survey uses three telescopes, two at Apache Point, New Mexico, and one in northern Chile. Their mission is to improve the accuracy of cosmological measurements and map large- and small-scale structure in our universe. It’s within this context that something funny was found. Maybe it’s not so funny as it seems to contradict that basic tenant I referred to above.
So, at the virtual American Astronomical Society meeting in June 2021, cosmologist Alexia Lopez of the University of Central Lancashire in Preston, England, and colleagues, reported their funny findings.
First of all, the technology used to acquire this data is mind boggling! They were able to examine around 40,000 quasars over 9 billion light years away and detect in their halos magnesium atoms that had lost One Electron! Those atoms absorb light in a specific way, making them detectable. Well, upon analyzing their data it looked like the universe was smiling at them. Could be frowning too, depending on how the data is oriented. Nevertheless, the data showed an arc of quasars strung out for 3 billion light years. At that scale cosmology predicts there should be no organized patterns of matter.
Looking at the universe on smaller scales (less distant) we do see strings of giant galaxy clusters forming web-like matrixes and clumps of galaxies in clusters. That is very cool, but at nine billion light years away we shouldn’t see any large, organized structures. What’s going on?
Well, the arc isn’t exactly alone. There are other enigmatic large-scale objects.
The Sloan Great Wall – discovered in 2003, also using data from the Sloan Digital Sky Survey, is a billion light years away and extends nearly 1.4 billion light years. It’s a monster galaxy cluster filament.
The Giant Gamma Ray Burst Ring – discovered in 2015, is a loose ring of 9 gamma ray bursts. The ring is 9 billion light years away and measures over 5 billion light years in diameter. It might be associated with a large structure.
Then there’s the Hercules-Corona Borealis Great Wall, discovered in 2013. At about 10% the diameter of the observable universe it is the largest known structure.
So, what’s the big deal about the arc? It appears organized whereas the others are not.
What’s in the Sky?
November 7; 1 hour after sunset; southwest: A waxing crescent Moon and brilliant Venus share the sky
November 10; pre-dawn; east-southeast: Catch Mercury and Mars near the horizon