The Milky Way is our galactic home, a vast stellar island containing hundreds of billions of stars, including our own Sun. It is classified as a barred spiral galaxy, characterized by a flattened disk of stars and gas spanning approximately 100,000 light-years. This structure is one of an estimated two trillion galaxies scattered throughout the observable universe. Understanding the Milky Way’s “orbit” requires tracing its motion through increasingly massive cosmic structures. Its movement is not a simple orbit, but a complex trajectory governed by the cumulative gravitational pull of everything around it.
Movement within the Local Group
The immediate cosmic neighborhood of the Milky Way is the Local Group, a collection of over 80 galaxies. The Milky Way and the Andromeda Galaxy (M31) dominate the mass, dictating the motion of smaller dwarf galaxies.
The two large spiral galaxies are currently approaching each other at about 110 kilometers per second. This motion is a dance around a mutual center of mass, or barycenter, located between them. Their combined gravity overcomes the universe’s expansion on this local scale, pulling them closer.
This relative motion will culminate in a massive galactic collision in roughly four to five billion years, forming a new elliptical galaxy nicknamed “Milkomeda.” Newer models suggest there is roughly a 50% chance the galaxies will narrowly miss a direct head-on collision. Even if they pass, they will remain gravitationally entangled and eventually merge within the next ten billion years.
Falling Towards the Virgo Cluster
While the Milky Way and Andromeda interact, the entire Local Group moves as a unit toward a much larger structure: the Virgo Cluster. This cluster resides at the heart of the Virgo Supercluster. The Local Group is not orbiting the cluster, but is falling toward its gravitational center.
The Virgo Cluster is located approximately 65 million light-years away and contains an estimated 1,300 to 2,000 member galaxies, making it significantly more massive than the Local Group. This concentration of matter creates a powerful gravitational well that pulls on all surrounding galaxies.
Measurements of the microwave background radiation reveal that the Local Group is moving toward the Virgo Cluster at approximately 400 kilometers per second. This velocity results from the gravitational influences of the cluster’s thousands of galaxies, making the Virgo Cluster the dominant gravitational feature in our supercluster environment. This motion demonstrates the hierarchical nature of cosmic structure, where small groups are drawn to larger clusters.
The Great Attractor and the Flow of Laniakea
The Milky Way’s largest-scale motion lies within the Laniakea Supercluster, a colossal structure encompassing the Local Group and the Virgo Cluster. Laniakea, meaning “immense heaven,” is a vast cosmic web extending about 500 million light-years and containing the mass of 100,000 large galaxies.
The defining characteristic of Laniakea is the coherent flow of all its component galaxies toward a single, massive gravitational anomaly: the Great Attractor. This focal point is the ultimate driver of the Milky Way’s velocity through space. The Great Attractor is a massive concentration of dark matter and thousands of galaxies, including the Norma Cluster.
The Great Attractor lies between 150 and 250 million light-years from Earth. Its gravitational influence is the primary cause of the Milky Way’s peculiar velocity—the motion not due to the expansion of the universe. This pull causes the entire Local Group to hurtle toward it at approximately 600 kilometers per second.
The Great Attractor’s existence was confirmed by observing galaxy motions that deviated significantly from expected expansion. This anomaly is partially obscured from Earth by the Milky Way’s disk, a region known as the Zone of Avoidance. Despite the obscuration, the measurable flow of galaxies confirms the dominance of this mass concentration.
The flow toward the Great Attractor defines Laniakea as a gravitational basin, much like water flowing downhill toward a valley floor. Although the Laniakea Supercluster is not gravitationally bound and will eventually be dispersed by the accelerating expansion of the universe, this large-scale motion currently represents the Milky Way’s highest-level “orbit.” Our galaxy is one small component in a colossal stream, perpetually being pulled toward this immense gravitational center.