Astronomers Discover a Galactic Wall That Stretches 1 Billion Light-Years

Astronomers at the Canary Islands Institute of Astrophysics believe they've found what could be the largest cosmic structure ever discovered in space, New Scientist reports. The BOSS Great Wall—which comprises at least 830 galaxies—is so expansive that it would take light waves a billion years to reach from one end to the other, according to a study published in the journal Astronomy & Astrophysics [PDF].

Just like galaxies are made up of billions of stars drawn together by gravity, superclusters are formed by groups of galaxies. Galaxy filaments, the largest structures in the known universe, are made from far-reaching streams of hot gas that connect the superclusters together. These walls of galaxies stretch across space like a colossal web and account for half of the universe's mass.

Other galactic walls we've detected in our neighborhood of the universe include the Sloan Great Wall and the CfA2 Great Wall. The newly discovered BOSS Great Wall is at least two-thirds larger than both of them and possibly 10,000 times as massive as our own Milky Way.

Despite those numbers, not everyone is convinced of the BOSS Wall's status as the universe's new largest structure. “I don’t entirely understand why they are connecting all of these features together to call them a single structure,” astrophysicist Allison Coil of the University of California in San Diego told New Scientist. “There are clearly kinks and bends in this structure that don’t exist, for example, in the Sloan Great Wall."

One simple way to confirm the wall as a single structure would be to track all the galaxies and see if they are moving as one. But with the wall located between 4.5 and 6.4 billion light-years away from Earth, that's an impossibility for now.