Laniakea is the supercluster of galaxies that contains our Milky Way. Spanning roughly 500 million light-years across and holding about 100,000 galaxies, it represents the largest structure we belong to in the universe. The name comes from Hawaiian, meaning “immense heaven,” chosen to honor Polynesian navigators who used the stars to cross the Pacific Ocean.
How Laniakea Was Discovered
Before 2014, astronomers thought our cosmic address topped out at the Virgo Supercluster, a collection of galaxy groups centered on the Virgo Cluster. That picture changed when astronomer R. Brent Tully and his team published a landmark paper in the journal Nature on September 3, 2014. Instead of mapping galaxies by their positions alone, the team tracked their “peculiar velocities,” the way galaxies move relative to the overall expansion of the universe. These motions revealed something hidden: vast rivers of galaxies all flowing toward a shared gravitational center.
By tracing these flows, Tully’s team could draw boundaries around regions where all the galaxies stream inward toward the same point. Think of it like mapping watersheds on Earth. Rain falling on one side of a mountain ridge flows into one river basin, while rain on the other side flows into a different one. Laniakea is our cosmic watershed: the volume of space where everything is being pulled toward the same gravitational focal point. The old Virgo Supercluster didn’t disappear. It’s simply a smaller neighborhood within Laniakea, one piece of a much grander structure.
Size and Scale
Laniakea contains the mass of roughly 100 million billion suns, distributed across an estimated 100,000 galaxies. Its diameter stretches about 500 to 520 million light-years. To put that in perspective, the Milky Way is about 100,000 light-years across, meaning you could line up roughly 5,000 galaxies our size end to end and still not span the full width of Laniakea.
The Milky Way sits in the outskirts of this structure, not near the center. We’re part of the Local Group (a small cluster of a few dozen galaxies), which belongs to the Local Sheet, which in turn is one small filament within Laniakea’s broader web. Brent Tully himself joked about the naming conventions at smaller scales: “We live in the Local Group, which is part of the Local Sheet next to the Local Void. We wanted to come up with something a little more exciting than ‘Local.'”
The Great Attractor at the Center
At the heart of Laniakea lies the Great Attractor, a region that puzzled astronomers for decades. First identified in the 1970s and 1980s, the Great Attractor seemed to be pulling our galaxy and thousands of others toward a point in space obscured by the dusty plane of the Milky Way itself, making it difficult to observe directly.
Laniakea’s discovery finally put the Great Attractor in context. It’s not a single massive object like a giant galaxy or black hole. It’s a place: the central gravitational point of the entire Laniakea supercluster. All 100,000 galaxies within Laniakea are drifting toward this region, drawn by the collective gravitational pull of the mass concentrated there. The mystery wasn’t so much what the Great Attractor is, but what it belonged to, and the answer turned out to be a supercluster we didn’t know we were inside.
Laniakea’s Neighbors
Laniakea doesn’t exist in isolation. It borders several other superclusters, each defined the same way: as a basin of gravitational attraction where galaxies flow toward a shared center. A 2023 study using the CosmicFlows-4 catalog (the most detailed survey of galaxy distances and motions to date) confirmed Laniakea’s size and mapped five neighboring superclusters using the same watershed technique. These include Shapley, Perseus-Pisces, Hercules, Lepus, and Apus. Together, these structures form part of the cosmic web, the vast network of filaments, walls, and voids that makes up the large-scale architecture of the universe.
The Shapley Supercluster, located beyond Laniakea, is particularly significant. It’s one of the most massive concentrations of galaxies in the nearby universe, and its gravitational influence extends well into Laniakea’s territory.
A Possibly Much Larger Home
A decade after the original discovery, Tully’s team at the University of Hawaiʻi published new findings in 2024 suggesting that Laniakea may be only part of a far larger structure. Updated data now indicates a 60% probability that our galaxy belongs to a gravitational basin roughly 10 times larger in volume than Laniakea, centered on the Shapley concentration.
If confirmed, this would mean the original Laniakea is a sub-basin within something much grander, similar to how the Virgo Supercluster turned out to be a smaller piece of Laniakea. The challenge is that current cosmic surveys may not yet cover enough of the universe to map these immense basins completely. As co-author Ehsan Kourkchi put it, “Our cosmic surveys may not yet be large enough to map the full extent of these immense basins.” The seeds of cosmic structure planted in the earliest moments of the universe may have grown far larger than existing models predict.
Why It Matters
Laniakea changed how astronomers define superclusters. Before 2014, superclusters were identified by eye, essentially by looking for regions where galaxies seemed to clump together on the sky. Tully’s team replaced that approach with something more physical: defining superclusters by the motion of galaxies, by where gravity is actually pulling matter. This gave superclusters clear, measurable boundaries for the first time.
For the rest of us, Laniakea provides a sense of cosmic address. You live on Earth, which orbits the Sun, which sits in the Milky Way, which belongs to the Local Group, which is part of the Virgo Supercluster, which is one region within Laniakea. And Laniakea itself may be nested inside something even larger. Each layer was invisible until someone found the right way to look.