The Laniakea Supercluster is the vast web of galaxies our Milky Way belongs to. It stretches about 520 million light-years across, holds roughly 100,000 galaxies, and was mapped and named in 2014. Think of it as our home neighborhood on the largest scale anyone has ever drawn.
You know your home address by heart. House number, street, city, country. Maybe, on a good day, you can picture Earth spinning in the solar system. But keep zooming out, past the planets, past the Sun, past the Milky Way itself, and eventually you reach the biggest address humans have ever written down for ourselves. It has a name, and the name is Laniakea. For most of history we had no idea it was there. Then in 2014 a team of astronomers pulled it out of the dark, and suddenly our little galaxy had a much bigger home than anyone expected.
Key Takeaways
- Laniakea is the supercluster of galaxies that contains the Milky Way, spanning about 520 million light-years and holding roughly 100,000 galaxies.
- Astronomers defined and named it in 2014 by tracking how galaxies drift, not just where they sit.
- The name is Hawaiian for “immense heaven,” a nod to Polynesian navigators who read the sky to cross the Pacific.
- Despite being enormous, Laniakea is not held together by gravity. Dark energy is expected to pull it apart over cosmic time.
- It is not the largest structure in the universe. Bigger cosmic walls and filaments exist, and Laniakea itself may be part of something larger still.
Zooming Out From Home
Start where you are and keep pulling the camera back. Earth sits in the solar system, one star and its huddle of planets. The solar system sits inside the Milky Way, a spiral of a few hundred billion stars. The Milky Way runs with a small crowd of nearby galaxies called the Local Group, held together with Andromeda as the other heavyweight. Zoom out again and the Local Group turns out to be a tiny piece of a much larger collection of galaxy groups and clusters. That is the neighborhood Laniakea maps.
Here is the whole ladder in one view, so the jumps in scale actually land.
| Structure | What it holds | Rough size across |
|---|---|---|
| Solar System | The Sun and everything orbiting it | about 2 light-years |
| Milky Way | 100 to 400 billion stars | about 100,000 light-years |
| Local Group | 50-plus galaxies, led by the Milky Way and Andromeda | about 10 million light-years |
| Virgo Supercluster | Thousands of galaxies, our old “home supercluster” | about 110 million light-years |
| Laniakea Supercluster | Around 100,000 galaxies | about 520 million light-years |
Notice the last two rows. For a long time astronomers thought the Virgo Supercluster was the top of our address. Laniakea swallowed that idea whole, because it turned out the Virgo Supercluster is only one lobe of something far bigger. If the leap from a solar system to a galaxy already stretches your head, our guide to how vast the universe really is keeps climbing past even this.
A map of the superclusters near us, with Laniakea marked out from its surroundings. The Milky Way sits far out on the edge, not anywhere near the center. (Image: Andrew Z. Colvin / Wikimedia Commons, CC BY-SA)
What Actually Is a Supercluster?
Galaxies are social. They rarely sit alone. They gather into groups of a few dozen, and those groups gather into clusters of hundreds or thousands, and the clusters string together into the largest patterns in existence. A supercluster is one of those top-level patterns, a sprawling collection of galaxy clusters linked by long filaments with huge, near-empty voids in between.
The tricky part has always been where to draw the line. Superclusters do not come with fences. One blurs into the next, and for decades nobody could agree on where our own supercluster ended. That is exactly the problem the Laniakea team set out to solve, and the way they solved it is the clever bit of this whole story. Our explainer on the difference between a galaxy and a solar system is a good primer if these tiers are still settling into place for you.
How Astronomers Drew the Map
Most maps of the sky show you where things are. The Laniakea map is different. It shows you where things are going.
In 2014 a team led by R. Brent Tully at the University of Hawaii, working with Hélène Courtois, Yehuda Hoffman, and Daniel Pomarède, measured the motions of about 8,000 galaxies. Not just their positions, but the direction and speed each one is drifting once you subtract the general expansion of the universe. When they mapped those motions, a shape appeared. Across a huge region, galaxies were all sliding toward one common gravitational basin. Cross an invisible line, and galaxies started flowing the other way instead, toward a different basin.
That dividing line is the edge of Laniakea. The team defined our supercluster as everything that flows inward toward the same center, a bit like a watershed on Earth, where every drop of rain on one side of a ridge drains into the same valley. Everything whose rivers run to our valley is Laniakea. The result was published in the journal Nature, and it redrew the boundaries of our cosmic home.
The Great Attractor at the Center of It All
If every galaxy in Laniakea is sliding toward one point, what is at that point?
Astronomers call it the Great Attractor, a region of enormous mass tugging on everything around it, including us. The Milky Way is drifting toward it right now at hundreds of kilometers every second. The strange thing is that we cannot get a clear look at the Great Attractor, because it sits behind the crowded, dusty plane of our own galaxy, in a patch of sky so blocked by stars and gas that astronomers call it the Zone of Avoidance. So the thing pulling our entire supercluster around is partly hidden from view, and we mostly know it by its pull rather than its face.
What the Name Means
Laniakea is a Hawaiian word, and it was chosen with care. It means “immense heaven,” from lani for heaven and ākea for spacious or immeasurable. A Hawaiian language teacher named Nawaʻa Napoleon suggested it, partly to honor the Polynesian navigators who once crossed thousands of miles of open Pacific using nothing but the stars, the swells, and memory. There is something fitting about that. The people who read the sky to find their way home lent their word to the largest home we have ever found.
A Kingdom That Won’t Last
Here is the twist most people miss. Laniakea is gigantic, but it is not really a solid, permanent object. It is not held together by gravity the way a galaxy or even a galaxy cluster is.
The universe is expanding, and that expansion is speeding up, driven by dark energy. Follow-up studies after the 2014 discovery found that Laniakea’s own gravity is not strong enough to win against that outward push. Over cosmic timescales, most of the supercluster is expected to drift apart rather than hold together, with different pieces eventually carried out of reach of one another. So Laniakea is less a fortress and more a snapshot, the shape our corner of the cosmos happens to have right now, caught in the middle of slowly coming undone.
So, Is Laniakea the Biggest Thing Out There?
You will see Laniakea called “the largest structure in the universe.” It is a great headline. It is also not true.
Laniakea is one of the larger structures we belong to, but the universe has bigger. Astronomers have mapped cosmic walls and filaments that dwarf it, including the South Pole Wall and the enormous Hercules-Corona Borealis Great Wall, which spans billions of light-years. On top of that, Laniakea appears to be flowing toward an even bigger concentration of mass called Shapley, and it may itself be just a component of a larger complex. So rather than the biggest object in existence, Laniakea is better understood as our address, the specific patch of the cosmic web where the Milky Way lives. That is remarkable enough without the exaggeration. For a sense of just how many galaxies fill the wider universe beyond it, our look at how many solar systems fill the Milky Way starts the count much closer to home.
Frequently Asked Questions
What is the Laniakea Supercluster? It is the supercluster of galaxies that our Milky Way belongs to. Defined in 2014, it spans roughly 520 million light-years and contains about 100,000 galaxies, all connected by the pull of gravity into one flowing region of the cosmic web.
How big is Laniakea? About 520 million light-years across, with an estimated mass of 100 quadrillion Suns, which is roughly 100,000 times the mass of the entire Milky Way. Light itself would need hundreds of millions of years just to cross it.
Why is it called Laniakea? The name is Hawaiian for “immense heaven.” It was chosen to honor the Polynesian navigators who used the stars to cross the Pacific Ocean, connecting an ancient way of reading the sky to a very modern map of it.
Is Laniakea the largest structure in the universe? No. It is one of the larger structures we are part of, but bigger cosmic walls and filaments exist, such as the Hercules-Corona Borealis Great Wall. Laniakea may even be a piece of a still-larger complex.
Will the Laniakea Supercluster stay together? Most likely not. Its gravity is not strong enough to overcome the accelerating expansion of the universe, so over immense stretches of time it is expected to disperse rather than hold together as a single object.
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