The Milky Way and every galaxy near it are drifting through space at hundreds of kilometers per second toward a patch of sky that telescopes struggle to see directly. Astronomers first detected the pull in the 1980s by noticing that galaxies across a huge swath of the nearby universe were not moving quite the way the expansion of space alone would predict.
That deviation led to the discovery of a massive concentration of matter that researchers still refer to by the name they gave it decades ago, even though the object behind the pull sits almost directly behind the crowded plane of the galaxy, making it one of the hardest large structures in the observable universe to study head-on.
A Region of Gravity, Not a Single Object
The term does not describe one galaxy, star or black hole. It refers to a broad concentration of mass spread across a region of intergalactic space, estimated to total on the order of 10 quadrillion solar masses, that creates a dip in the local gravitational field strong enough to bend the paths of galaxies hundreds of millions of light-years away. It sits at the apparent gravitational center of the Laniakea Supercluster, the broader structure of roughly 100,000 galaxies that includes the Milky Way, according to the entry maintained on Wikipedia.
Hidden Behind the Milky Way’s Own Disk
Studying the region directly is difficult because it lies behind the Milky Way’s galactic plane, in a strip of sky astronomers call the Zone of Avoidance, where the dust and stars of the galaxy’s own disk block most visible light from anything farther out. The Norma and Triangulum Australe constellations mark roughly the direction where the pull originates, and NASA’s Hubble Space Telescope has captured images of the Norma Cluster region, one of the few ways to study a part of the structure that visible-light instruments can reach at all, according to NASA’s Hubble mission page.
Discovered by Tracking Galaxies That Would Not Behave
The pull was identified in 1986 by a team of seven astronomers, informally nicknamed the Seven Samurai, who measured distances to about 400 elliptical galaxies using a method that compares a galaxy’s brightness and the speed of its internal star motion. When they combined those distance estimates with each galaxy’s redshift, they found that galaxies across a wide stretch of sky were moving faster or slower than the uniform expansion of the universe alone would explain. The team concluded that a large, unseen mass concentration was pulling on all of them, and gave that concentration the name that has stuck ever since.
How Fast Everything Nearby Is Moving Toward It
The evidence for the pull comes from what astronomers call peculiar velocities, the portion of a galaxy’s motion left over after subtracting the expansion of space itself. Across the region influenced by the structure, those peculiar velocities range from roughly 700 kilometers per second toward the attractor to 700 kilometers per second away from it, depending on a galaxy’s position relative to the pull. The Local Group, the cluster of galaxies that includes the Milky Way and Andromeda, is itself among the galaxies streaming in that general direction, part of a much broader flow of matter across hundreds of millions of light-years.
A Massive Galaxy Cluster at the Center
Extensive follow-up work through the 1990s and 2000s used X-ray observations, which can penetrate the dust that blocks visible light, to identify the Norma Cluster, also catalogued as Abell 3627, as the dominant galaxy cluster near the center of the attracting region. The Norma Cluster sits roughly 220 million light-years from the Milky Way and contains an unusually large number of old, massive galaxies, some of which are actively colliding with their neighbors and emitting strong radio signals as a result. A large galaxy filament called the Norma Wall, sometimes referred to as the Great Attractor Wall, extends through the same region and links several other galaxy clusters together.
Not the Final Destination
Later surveys found a twist: the Great Attractor itself appears to be moving toward an even larger concentration of mass farther away, called the Shapley Supercluster, sometimes called the Shapley Attractor. That discovery suggested the original 1986 measurement had captured only part of a much larger gravitational picture, with the nearer structure acting as a way station rather than the ultimate source of the pull. Researchers have since folded the Great Attractor into the broader concept of the Laniakea Supercluster, a loosely bound structure spanning roughly 500 million light-years that is not dense enough to stay gravitationally bound together permanently, but is held in a temporary, shared pattern of motion by the same gravitational basin that first revealed itself through the peculiar velocities of galaxies decades ago.
This article was produced with the assistance of AI and reviewed by an editor.
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