We are not alone in the Universe.
Our galaxy, I mean. The Milky Way is one of a couple of trillion galaxies in the observable Universe. Those galaxies are not evenly distributed, either: Some are by themselves in the local space around them, while others are in small groups of a few dozen galaxies, and still others are in huge clusters with hundreds or thousands of other galaxies. Even that's not the top of the scale, with clusters themselves clustering into superclusters.
We are in a small group we parochially call the Local Group. But we exist in the outer suburbs of a cluster of two thousand galaxies called the Virgo Cluster, the heart of which is about 60 million light years away in the constellation Virgo (hence the cluster's name).
We know quite a bit about the galaxies in the cluster, but we can also learn more from the galaxies around it; nearby but not in it. They're affected strongly by the cluster, depending on the cluster's mass and their distance from it, so by getting an accurate distance to these galaxies we can learn more about the cluster they live near. Some astronomers used the Hubble Space Telescope ...