Bright background quasars shine light through the gas around galaxies. Some of the light from the quasar is then absorbed by the gas and leaves a signature feature behind in the quasar spectrum. Astronomers use this information to map the matter distribution in distant space.

A University of Louisville astronomy and astrophysics professor is part of an international team of researchers working on a discovery that could change one of the basic concepts of the cosmos.

Gerard Williger and two colleagues at the Jeremiah Horrocks Institute at the University of Central Lancashire (UCLan), in Preston, England, presented the research last month at a virtual meeting of the American Astronomical Society. 

Williger, a fellow at the institute, is a co-advisor with UCLan’s Roger Clowes to UCLan PhD student Alexia Lopez. They are investigating Lopez’s discovery of an arc of galaxies in distant space they have named the Giant Arc. 

Spanning 3.3 billion light years, the Giant Arc might be an indicator that scientists need to expand the size of what is considered a representative segment of all of space in the Cosmological Principle. This guiding principle holds that one portion of the cosmos is effectively the same as the rest, so findings from that segment apply to all of space.

“The Cosmological Principle tells us one part of the universe is pretty much the same as another part of the universe,” Williger said. “The Giant Arc is three times bigger than anything we’ve seen before. So maybe that principle has to have its size upgraded. How big is big enough to say this is an average piece of the universe?”

An article published June 10 in Science News quoted Lopez as saying the discovery, if true, adds to a growing body of similar research that “would overturn cosmology as we know it.”

The arc was discovered by analyzing data from the Sloan Digital Sky Survey