Astronomers have discovered that there is a vast wall across the southern border of the local cosmos.

The South Pole Wall, as it is known, consists of thousands of galaxies — beehives of trillions of stars and dark worlds, as well as dust and gas — aligned in a curtain arcing across at least 700 million light-years of space. It winds behind the dust, gas and stars of our own galaxy, the Milky Way, from the constellation Perseus in the Northern Hemisphere to the constellation Apus in the far south. It is so massive that it perturbs the local expansion of the universe.

An international team of astronomers led by Daniel Pomarède of Paris-Saclay University and R. Brent Tully of the University of Hawaii announced their findings in a paper in Astrophysical Journal.

“The surprise for us is that this structure is as big as the Sloan Great Wall and twice as close, and remained unnoticed, being hidden in an obscured sector of the southern sky,” Pomarède said of the conglomeration, which is in an area astronomers call the “zone of avoidance.”

“The discovery is a wonderful poster child for the power of visualizations in research,” Tully said.

The wall joins a host of other cosmographic features: arrangements of galaxies, or a lack of them, that astronomers have come to know and love over the past few decades, with names like the Great Wall, the Sloan Great Wall, the Hercules-Corona Borealis Great Wall and the Bootes Void.

The new paper was based on measurements, performed by Tully and his colleagues, of the distances of 18,000 galaxies as far away as 600 million light-years. By comparison, the most distant objects we can see are about 13 billion light-years away.

One astonishing aspect of the wall is how big it is compared to the volume that the team was surveying: a contiguous filament of light 1.4 billion light-years long, packed into a cloud maybe 600 million in radius. “There is hardly room in the volume for anything bigger!” Tully said.