Other researchers caution that evidence in the new discovery isn't strong enough to challenge this notion of large-scale uniformity, dubbed the cosmological principle.
But, they add, the work does highlight a key question in modern cosmology: What is the size scale at which the wildly uneven distribution of matter seen at small cosmic scales gives way to a uniform average across the universe as a whole?
"We don't know that," says Margaret Geller, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., whose research focuses on how the universe and its cosmic-scale structures formed and evolved. "And this is an indication that we don't know that."
Astronomers snagged their first large cluster of quasars in 1982, says Roger Clowes, an astronomer at the University of Central Lancashire in Britain and the leader of the research team reporting the new results. By 1991, two more large clusters had been found. With the advent of the Sloan Digital Sky Survey in 2000, more have appeared, including the latest discovery.