The biggest thing in the universe

British astronomers have identified a celestial object so large that it challenges scientists’ basic assumptions about the nature of the universe. Huge-LQG is a cluster of 73 quasars, each of which lies at the center of its own galaxy.The structure measures 4 billion light-years across at its greatest dimension; our own Milky Way galaxy, which is 100,000 light-years across, is a speck in comparison.

But the conundrum of Huge-LQG—the letters stand for Large Quasar Group-isn’t its immense size alone but also its location, astronomer Roger Clowes, of the U.K.s University of Central Lancashire, tells the Toronto Star. Not far away, at least in cosmic terms, is another immense quasar cluster.The size and proximity of the two objects, Clowes says, confound the so-called cosmological principle, which holds that the universe is essentially homogenous, and looks the same in every direction, regardless of the viewer’s vantage point.That principle has allowed astronomers to assume that parts of the universe they have not observed are fundamentally similar to the known parts. Clowes calls the discovery of Huge-LQG “the most dramatic challenge” yet to that reassuring assumption.

“The structure we found is a few percentage points, say 5 percent, of the size of the observable universe,” he says. “It makes it hard to say the universe is uniform.”