A Controversy Among the Cosmos
Rubi Orellana
In the distant universe, a large arc of galaxies spans more than three billion light-years. If the claims being presented are accurate, they would call into question a fundamental cosmological assumption: that matter in the cosmos is uniformly distributed on enormous sizes regardless of viewpoint.
"It would overthrow cosmology as we know it," Alexia Lopez said at the Virtual American Astronomical Society Meeting on June 7. “However, to put it mildly, our typical model falls short."
By examining the light from 40,000 quasars collected by the Sloan Digital Sky Survey, Lopez and colleagues from the University of Central Lancashire in Preston, England, found the alleged structure, which they call the Giant Arc. Quasars are the centers of massive galaxies that are so far away that they appear as light points. Some of the light is absorbed by atoms and foreground galaxies on their way to the Earth, creating unique fingerprints in the light that reaches the astronomers' instruments.
Magnesium atoms that have lost only one electron in the halos of galaxies estimated to be 9.2 light-years distant bear the Giant's Arc signal. The quasar light absorbed by these atoms forms a nearly symmetrical arc spanning one-fifteenth the radius of the visible universe, covering hundreds of galaxies. The structure is invisible to human eyes in the sky, but if it were visible, the arc would cover around 20 times the breadth of the full moon.
Subir Sarkar of the University of Oxford, an astrophysicist who investigates large-scale structures in the cosmos, isn't persuaded yet. "Our eyes have a proclivity for picking up patterns." Some people have claimed to observe cosmologist Stephen Hawking's initials inscribed in fluctuation in the cosmic microwave background, Sarkar shared with Science News. Therefore, it is unlikely the claims being made are true.
Lopez used three statistical tests to determine the likelihood of the galaxies aligning in a huge arc by coincidence. All three tests indicated that the structure is real, with one test exceeding physicists' gold standard of less than 0.00003 percent chance of being a statistical fluke. "That sounds nice, but Sarkar thinks it might not be enough." More evidence from Lopez's group and others might either corroborate or disprove the Giant Arc. If true, the Giant Arc would join a growing number of large-scale formations in the universe that, when combined, would defy cosmology's mainstream model. This model implies that matter is dispersed uniformly over big enough areas of space (more than 1 billion light-years).
“It's possible that one large-scale structure is merely a statistical fluke," Lopez added. “That isn't the issue. The sum of all of them is what exacerbates the situation."
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