What Is The Great Attractor?

The universe is filled with mystery. There is likely far more that remains unknown about the cosmos compared to what we do know. A prime example of this is a region of the universe known as the Great Attractor. The Great Attractor is a gravitational anomaly, with its gravitational field pulling on the galactic supercluster that contains our galaxy. The mass of the Great Attractor is many millions of times higher than the Milky Way, yet unfortunately, it is hidden from view. In a perfect example of cosmic inconvenience, the Great Attractor is located behind the plane of the Milky Way, and so our own galaxy is blocking our ability to see the Great Attractor. 

An Intergalactic Anomaly

Great Attractor
Hubble image of the approximate region of the Great Attractor. Image credit: NASA/ESA

The Great Attractor was discovered through its gravitational influence on our galaxy and hundreds of others located within the Local Group of galaxies. The existence of the Great Attractor was first proposed in the 1970s, after astronomers discovered that the Milky Way and all the other galaxies around it appeared to be moving towards a single source. Whatever the Great Attractor is, it is massive enough that it is able to pull on entire galaxy clusters over a distance of many millions of light years. Estimates on the distance to the Great Attractor place it around 250-million light years away in the constellations Triangulum Australe and Norma. 

Our galaxy, along with millions of others, are believed to exist in a gigantic supercluster of galaxies known as the Laniakea Supercluster, which spans a distance of 500-million light years. Interestingly, the Laniakea Supercluster does not possess enough mass to be gravitationally bound, and thus it should be dispersing. However, the entire supercluster appears to be bound to the Great Attractor, which astronomers believe may be the focal point of the Laniakea Supercluster. 

Not A Thing, But A Place

Triangulum Galaxy
All nearby galaxies, such as the Triangulum Galaxy, are moving towards the Great Attractor. Image credit: NASA/ESA

It is important to note that the Great Attractor may not be an object per say. Rather, it is a region of space that is likely the center of gravity of the Laniakea Supercluster. Over time, every galaxy in the supercluster is moving towards the Great Attractor. Eventually, every galaxy within the Laniakea Supercluster will condense in this region of space, spelling the end of our local region of the cosmos. However, this will probably never happen. Despite the gravitational force of the Great Attractor, it is far weaker than the expansion of space due to dark energy. Before the Great Attractor could ever swallow our galaxy and those near it, dark energy will have caused the entire Laniakea Supercluster to break apart, and the Great Attractor will likely cease to exist along with it.