What's the biggest known structure in the universe?

Astronomers used to think it was a "filament" of galaxies known as the Sloan Great Wall. But recent research suggests a different structure is even bigger -- and its size has astronomers scratching their heads.

Meet the Hercules-Corona Borealis Great Wall (Her-CrB GW). Check it out in the video above.

"The Her-CrB GW is larger than the theoretical upper limit on how big universal structures can be," Dr. Jon Hakkila, an astrophysics professor at the College of Charleston in South Carolina and one of the astronomers who discovered the structure, told The Huffington Post in an email. "Thus, it is a conundrum: it shouldn't exist but apparently does."

Mysteries just like this are why astronomers scan the skies for a glimpse into the past, as they shed light not only on the early years of our universe, but also more about our galaxy, our solar system, and ultimately, ourselves.

"We are now mapping structures across the sky," astronomer Dr. Jay M. Pasachoff, director of the Hopkins Observatory at Williams College in Williamstown, Mass., who was not involved in the great wall's discovery, told The Huffington Post. "We’re learning how the universe grew up. So we’re learning about how our cluster of galaxies grew up and how our own galaxy grew up and how our sun formed, and how the Earth formed soon there after. We’re looking back at our history."

Because astronomers are still mapping the sky, there just may be something even grander than the Hercules-Corona Borealis Great Wall in our universe.

"The danger of finding the biggest, or most distant, or the oldest things in the universe is always that sooner or later someone is likely to come along and find something bigger, more distant, or older than the thing you found," Hakkila said. "So far we have not been upstaged, but it has only been about six months since we published."

The finding was published in the journal Astronomy & Astrophysics.