The Great Attractor
Later explainedSummary
The Milky Way, and a great many galaxies around it, are falling toward something. Not drifting: falling, at something like six hundred kilometres per second, over and above the general expansion of the universe.
Something out there has enough mass to pull an entire region of the cosmos toward it, and for decades nobody could see what.
The reason nobody could see it is very simple and slightly embarrassing. It is directly behind our own galaxy.
What is documented
The motion. From the 1970s, surveys of galaxy velocities established that the Local Group, and the larger structure it sits in, has a substantial peculiar velocity: a motion that is not accounted for by the expansion of the universe. It is directed toward a region in the constellations of Centaurus and Hydra.
The Zone of Avoidance. That direction lies almost exactly in the plane of the Milky Way's disc.
The disc of our galaxy is full of stars, gas and dust, and it is opaque. Looking through it in visible light is like trying to see a lighthouse through a hill. Astronomers call the region it blocks the Zone of Avoidance, and it covers a substantial fraction of the sky.
The thing pulling us was sitting in it.
Seeing through. The problem was solved by not using visible light. X-ray, infrared and radio observations pass through the dust, and surveys in those bands were able to map the region behind the galactic plane.
What is there. A large concentration of mass, containing the Norma Cluster, a massive galaxy cluster, together with other clusters and groups. It is not an object. It is a region: a great overdensity of ordinary matter, galaxies by the thousand, doing exactly what mass does.
The larger picture. In 2014, Tully and colleagues published a mapping of the local flows of galaxies and defined the supercluster in which the Milky Way sits, naming it Laniakea. On that map, the Great Attractor lies near the gravitational focus, and our galaxy is out on the edge.
And it is not the whole story. Later work indicates that a significant part of our motion is due to the Shapley Supercluster, an even larger concentration lying beyond the Great Attractor in roughly the same direction. Some analyses attribute a greater share of the pull to Shapley than to the Great Attractor itself.
And something is pushing. In 2017, Hoffman and colleagues identified what they termed the Dipole Repeller: a large underdense region on the opposite side of the sky. An underdensity does not pull. Relative to everything around it, it pushes.
Our motion is the sum of a pull from one side and a push from the other.
Leading explanations
A large concentration of ordinary mass, obscured by the Milky Way. Established.
There is no exotic physics here and there never was. The Great Attractor is galaxies. A great many of them, in a large volume, exerting gravity in the entirely ordinary way.
Why it was hard. Not because the object is strange, but because our vantage point is bad. We are inside a dusty disc, and we were trying to look through the thickest part of it.
This is a general and rather humbling feature of cosmology. A very large fraction of the sky is simply unavailable to us in visible light, and it will be for as long as we live in a spiral galaxy.
What the popular version gets wrong
"The Great Attractor is a mysterious object." It is not an object. It is a region of higher-than-average galaxy density. The name is unfortunate; it was coined for a gravitational effect whose source had not been seen, and it has made a supercluster sound like an entity.
"Nobody knows what it is." It is a supercluster region containing the Norma Cluster and others. It has been mapped in X-ray, infrared and radio.
"We are being dragged toward our doom." We are not. The expansion of the universe is, on the largest scales, winning. The Local Group is bound to itself and to nothing else that far away, and the expansion will carry the Great Attractor beyond our reach long before anything arrives anywhere.
"It might be a black hole, or dark matter, or something unknown." It is galaxies. We have counted a lot of them.
Current status
Later explained. The source of the flow is identified as a concentration of ordinary mass, and the picture has been refined since: Laniakea, Shapley, and a repelling underdensity on the far side.
The registry keeps this record because of the shape of the mistake it corrects. For decades this was described as one of the great unsolved puzzles of cosmology, and it was framed as a question about the universe.
It was a question about the Milky Way. The thing was never hidden. We were standing in the way.
Sources
- Lynden-Bell, D. et al. (1988). Identification of the large-scale streaming motion and the term Great Attractor.
- X-ray, infrared and radio surveys of the Zone of Avoidance, and the identification of the Norma Cluster (Abell 3627).
- Tully, R. B., Courtois, H., Hoffman, Y. and Pomarède, D. (2014). "The Laniakea supercluster of galaxies." Nature 513, 71-73.
- Hoffman, Y., Pomarède, D., Tully, R. B. and Courtois, H. (2017). "The Dipole Repeller." Nature Astronomy 1, 0036.
- Subsequent literature on the relative contributions of the Great Attractor and the Shapley Supercluster to the local flow.
Last reviewed: July 2026. Records are provisional. Where the evidence changes, the entry changes. Found an error? Tell us.