The Milky Way sits near the edge of a gravitationally bound cluster of about 40 galaxies called the Local Group, which itself lies on the outskirts of a much larger structure called the Virgo Supercluster. There’s no fixed “center” of the universe to measure from, but astronomers have mapped our galaxy’s position at every scale, from our neighborhood of galaxies all the way out to the largest structures ever observed.
Our Place in the Local Group
The Milky Way is one of two dominant galaxies in the Local Group, a collection of roughly 40 galaxies spread across a volume about 10 million light-years in diameter. The other heavyweight is the Andromeda Galaxy, located about 2.65 million light-years away. Andromeda is slightly larger, with a diameter of around 140,000 light-years compared to the Milky Way’s 100,000. A third spiral galaxy, the Triangulum Galaxy, rounds out the major members, though it’s considerably smaller. Most of the remaining galaxies in the Local Group are small dwarf galaxies gravitationally tethered to either the Milky Way or Andromeda.
The two big spirals are heading toward each other at roughly 250,000 miles per hour. Their first close pass will happen about 4 billion years from now, warping both galaxies as gravity stretches and distorts their shapes. Over the following 2 billion years, repeated collisions will scatter stars into new orbits and eventually merge the pair into a single giant elliptical galaxy. The Sun will likely survive this process, though it will orbit in a very different-looking galaxy.
On the Edge of a Supercluster
Zoom out further and the Local Group is just one of about 50 small galaxy groups orbiting a much denser region: the Virgo Cluster. Together, these groups and the Virgo Cluster form the Local Supercluster (also called the Virgo Supercluster), a flattened structure spanning over 100 million light-years. The Milky Way is near one edge of this supercluster, not near its center. Our entire Local Group appears to be revolving around the supercluster’s core at about 400 kilometers per second.
In 2014, astronomers identified an even larger structure called Laniakea, a supercluster of superclusters containing over 100,000 galaxies. The Virgo Supercluster is one basin of attraction within Laniakea. At this scale, gravity pulls galaxies along vast channels toward dense regions, like streams flowing downhill.
Between a Void and a Dense Cluster
One of the most striking features of the Milky Way’s location is that it sits right at the boundary between a region packed with mass and a region almost empty of it. On one side is the Virgo Cluster, pulling us toward its enormous concentration of galaxies. On the other side is the Local Void, a vast, mostly empty region first identified in 1987. As this void expands and empties further, it effectively pushes galaxies at its edges away.
For decades, astronomers noticed that the Milky Way, Andromeda, and their neighbors are deviating from the overall expansion of the universe by over 600 kilometers per second (about 1.3 million miles per hour). Research from the University of Hawaiʻi showed that roughly half of this extra motion comes from the combination of being pulled toward the Virgo Cluster and pushed away from the expanding Local Void. Our galaxy is, in a sense, caught between two cosmic forces.
Where the Sun Sits Inside the Milky Way
Within the Milky Way itself, our solar system is about 25,800 light-years from the galactic center, where a supermassive black hole called Sagittarius A* sits. That distance is actually closer than the 27,700 light-years astronomers accepted for decades. Updated measurements from the Japanese VERA radio telescope project revised the number downward by about 1,900 light-years.
The Sun orbits the galactic center at about 227 kilometers per second, completing one full lap every 225 to 250 million years. We’re located in what’s called the Orion Spur, a minor arm branching off between two of the galaxy’s major spiral arms. It’s not a prominent feature of the Milky Way’s structure. Think of it as a side street between two highways. Our position roughly halfway out from the center and nestled in a relatively quiet arm is one reason our night sky isn’t overwhelmed by the light of densely packed stars.
No Center of the Universe
A natural follow-up question is: where is all of this relative to the center of the universe? The answer is that there isn’t one. The universe is expanding, but not outward from a single point. Every point in space is moving away from every other point, like dots on the surface of an inflating balloon. From any galaxy’s perspective, all other galaxies appear to be receding.
What we can say is that the observable universe, the sphere of space from which light has had time to reach us, is centered on us by definition. That sphere has a radius of about 46.5 billion light-years. But an observer in the Andromeda Galaxy would have their own observable universe centered on them, overlapping with ours but not identical. The Milky Way doesn’t occupy a special location. It’s one galaxy among an estimated two trillion, positioned at the edge of a supercluster, straddling the border between a dense cluster and an enormous void, hurtling through space in multiple directions at once.