Scientists are finding that galaxies can move with each other across huge distances, and against the predictions of basic cosmological models. The reason why could change everything we think we know about the universe.
The Milky Way, the galaxy we live in, is one of hundreds of billions of galaxies strewn across the universe. Their variety is stunning: spirals, ring galaxies shaped like star-studded loops, and ancient galaxies that outshine virtually everything else in the universe.
But despite their differences, and the mind-boggling distances between them, scientists have noticed that some galaxies move together in odd and often unexplained patterns, as if they are connected by a vast unseen force.
Galaxies within a few million light years of each other can gravitationally affect each other in predictable ways, but scientists have observed mysterious patterns between distant galaxies that transcend those local interactions.
These discoveries hint at the enigmatic influence of so-called “large-scale structures” which, as the name suggests, are the biggest known objects in the universe. These dim structures are made of hydrogen gas and dark matter and take the form of filaments, sheets, and knots that link galaxies in a vast network called the cosmic web. We know these structures have major implications for the evolution and movements of galaxies, but we’ve barely scratched the surface of the root dynamics driving them.
Scientists are eager to acquire these new details because some of these phenomena challenge the most fundamental ideas about the universe.
“That’s actually the reason why everybody is always studying these large-scale structures,” said Noam Libeskind, a cosmographer at the Leibniz-Institut for Astrophysics (AIP) in Germany, in a call. “It’s a way of probing and constraining the laws of gravity and the nature of matter, dark matter, dark energy, and the universe.”
Why are distant galaxies moving in unison?
Galaxies tend to form gravitationally bound clusters that belong to even larger superclusters. Earth’s long-form cosmic address, for instance, would have to note that the Milky Way is part of the Local Group, a gang of several dozen galaxies. The Local Group is inside the Virgo supercluster, containing more than 1,000 galaxies. [ … ]