Circa 2020
Astronomers have found one of the largest structures in the known universe—a “wall” of galaxies that’s at least 1.4 billion light-years long. And given how close it is to us, it’s remarkable that we haven’t seen it before now.
What happened: An international team of scientists reported the discovery of the South Pole Wall in a paper published Thursday in the Astrophysical Journal. The structure is basically a curtain that stretches across the southern border of the universe (from the perspective of Earth) and consists of thousands of galaxies, along with huge amounts of gas and dust.
What do you mean by “wall”? Galaxies aren’t just strewn randomly throughout the universe. Along huge strands of hydrogen, galaxies collect into larger groupings of massive filaments, separated by giant voids of nearly empty space. Each filament is basically a wall of galaxies, stretching for hundreds of millions of light-years. They’re the biggest structures in the known universe. Other identified structures include the Great Wall, the Sloan Great Wall, the Hercules-Corona Borealis Great Wall, and the Bootes Void.