In the late 1930s, astronomer Harlow Shapley stared up at the sky and noticed something extraordinary — an enormous cloud of galaxies in the constellation Centaurus. It was a curiosity at the time, a shimmering patch of matter stretching across the depths of space. Today, we know this is no ordinary cluster but one of the largest known structures in the universe: the Shapley Concentration.
Recent work by astronomers at the University of Hawaii suggests that our own Milky Way may not be where we thought it was. Our galaxy, along with tens of thousands of others, might belong to a vast cosmic web linked to the Shapley Concentration, a region so enormous it cannot be comprehended.
“Our universe is like a giant web, with galaxies lying along filaments and clustering at nodes where gravitational forces pull them together,” said R. Brent Tully, the study’s lead researcher.
“Just as water flows within watersheds, galaxies flow within cosmic basins of attraction. The discovery of these larger basins could fundamentally change our understanding of cosmic structure.”
Tully and his team, working under the CosmicFlows project, have spent years studying the movements of 56,000 galaxies, and their latest findings suggest our cosmic neighborhood might be 10 times larger than previously thought.
Zooming Out To See A Colossal Cosmic Web
The universe’s largest structures have always boggled the mind. Galaxies aren’t just scattered randomly across space. Instead, they form a cosmic web — delicate filaments of gas and dark matter stretching for billions of light-years. This web is so enormous that it only began to come into focus in the 1980s when astronomers first developed instruments capable of observing these vast distances.
At the center of this web are superclusters, regions where galaxies cluster together, their gravity drawing in even more matter. For years, we believed our galaxy lived within the Laniākea supercluster, a sprawling region stretching 500 million light-years. But Tully’s new research suggests that Laniākea may be just one part of a much grander structure — the Shapley Concentration.
The Shapley Concentration is an immense basin of gravitational attraction. Galaxies don’t just sit still in space. Much like rivers flowing through valleys, galaxies drift along the paths set by these massive structures. And this flow may be carrying us far beyond Laniākea, into an even larger gravitational basin.
“We are still gazing through giant eyes,” said Ehsan Kourkchi, a co-author of the study, “but even these eyes may not be big enough to capture the full picture of our universe.”
Expanding Our Galactic View
If the Shapley Concentration is indeed pulling the Milky Way, it would mean our galaxy is part of a structure that could be up to 10 times larger than Laniākea. To put that into perspective, Laniākea already spans 500 million light-years and contains over 100,000 galaxies —making this new structure almost incomprehensibly vast.
The discovery hinges on the study of galaxy motion. By mapping the velocities of galaxies, Tully’s team was able to observe how gravity is pulling them across space. A galaxy caught between two massive structures gets tugged in multiple directions, with its motion revealing the gravitational forces at play. This technique, known as redshift surveying, has helped astronomers map out the large-scale structure of the universe.
And what they’ve found so far is remarkable. The Milky Way, along with its neighboring galaxies, appears to be moving toward the Shapley Concentration.
But this discovery also challenges our current models of the universe. For decades, astronomers have relied on the Standard Model of cosmology, which describes the universe’s expansion, dark matter, and dark energy. These forces have shaped the cosmos for billions of years, creating the vast structures we see today.
Yet, the Shapley Concentration and other similarly large structures push the boundaries of what our models can explain. According to the Standard Model, structures larger than about 1.2 billion light-years should not exist. But the Shapley Concentration — and another recent discovery known as the Sloan Great Wall — seem to defy that rule. These structures extend for billions of light-years, far beyond what cosmologists expected.
Looking Beyond The Milky Way
Tully’s team believes we’re only scratching the surface. Their work suggests that cosmic surveys might not be big enough to map the true scale of the universe’s largest structures.
“This discovery presents a challenge: our cosmic surveys may not yet be large enough to map the full extent of these immense basins,” said Kourkchi. “We are still gazing through giant eyes, but even these eyes may not be big enough to capture the full picture of our universe.”
The Shapley Concentration offers a glimpse into what lies beyond the edge of our current understanding. This ancient structure, born in the early days of the universe, formed from tiny fluctuations in density. Over billions of years, these fluctuations grew under the force of gravity, slowly pulling matter into the vast cosmic web we see today.
And while we can’t see all the components of this web — like the dark matter that makes up most of its mass — scientists have found clever ways to track its presence. By observing how galaxies move through space, they can map out the hidden forces shaping the universe.
The search for answers continues. As Tully’s team refines their surveys, they may uncover even larger structures.
The findings appeared in the journal Nature Astronomy.
