Introducing Quipu: The largest structure found in the universe

For years, scientists have worked to chart the universe’s massive structure, aiming to test key models of cosmology. These efforts also help uncover how galaxies form and change over time. While most studies rely on statistical descriptions, direct mapping reveals how these structures look and move in real space.

One of the most promising tools in this area is constraint reconstructions. This method uses real data to build models of how matter is spread across the nearby universe. These reconstructions don’t just offer a snapshot—they help show how cosmic matter has shifted and evolved.

Massive structures, including galaxy clusters and superclusters, can influence key values in astronomy. For example, local shifts in matter density affect the Hubble constant, which tracks how fast the universe is expanding. These gravitational structures can even tug on the data itself.

They also leave faint marks on the cosmic microwave background (CMB), the ancient light left over from the Big Bang. This happens through the Integrated Sachs-Wolfe effect, where large structures distort the CMB’s temperature slightly. Though subtle, these changes are measurable and meaningful.

Pinpointing these features is vital for accurate measurements of cosmic properties. Surveys like the 2MASS redshift survey and Cosmic Flow velocity compilations have provided extensive data for these regions. So far, astronomers have mapped regions out to a redshift of 0.03. That’s about 400 million light-years from Earth. But beyond this, there’s still much left uncharted.

Now, scientists are setting their sights on the region between redshifts 0.03 and 0.06. This range, from 425 million to 815 million light-years away, holds a vast amount of unmapped cosmic terrain. Exploring this space could unlock a better grasp of the universe’s structure.

Galaxy clusters help mark the path. Because of their size and brightness, they stand out as strong signals of where mass is located. Researchers have used them to build a fuller view of the universe’s hidden layout and better track the flow of matter.

To do this well, astronomers rely on X-ray data from surveys like CLASSIX. This survey blends results from two earlier ones—REFLEX in the southern sky and NORAS in the north. Together, these sources cover 86% of the sky, offering a powerful tool for mapping the cosmic web.

In their latest study, astronomers identified a structure that may be the largest known in the universe: Quipu. Named after the Incan system of knotted cords used for recording data, Quipu stretches 1.3 billion light-years across—more than 13,000 times the length of the Milky Way.

It consists of a long filament with multiple smaller filaments branching off, resembling its namesake. This colossal structure contains an estimated 200 quadrillion times the mass of the Sun, making it one of the most massive cosmic formations ever observed.

Researchers from the Max Planck Institute spotted Quipu while analyzing galaxy clusters in their target redshift range. "Quipu is actually a prominent structure readily noticeable by eye in a sky map of clusters in the target redshift range, without the help of a detection method," the team reported. The study, accepted for publication in Astronomy & Astrophysics, marks a major milestone in cosmic cartography.

Quipu is not alone in its grandeur. The researchers also identified four other massive superstructures, each rivaling some of the largest known formations in the universe. These include the Serpens-Corona Borealis superstructure, the Hercules supercluster, and the Sculptor-Pegasus superstructure, named for the constellations they span. The fifth is the Shapley supercluster, once thought to be the largest known cosmic structure.

Together, these five superstructures contain 45% of the known galaxy clusters, 30% of the observable galaxies, and 25% of the universe’s matter, occupying 13% of its volume.

Massive structures like Quipu have profound effects on their cosmic surroundings. Their immense gravitational pull distorts the space around them, bending light in a process called gravitational lensing. This phenomenon can magnify or warp distant galaxies, altering astronomical observations.

These superstructures also impact the cosmic microwave background by subtly shifting its temperature variations. This occurs through the Integrated Sachs-Wolfe effect, where the expansion of the universe slightly modifies the energy of CMB photons as they pass through large-scale structures. These alterations introduce foreground interference, making it harder to extract precise information about the early universe.

Furthermore, Quipu and similar formations influence measurements of the Hubble constant. While the universe is expanding, galaxies also have local motions due to gravitational interactions. These movements, known as peculiar velocities, must be accounted for when measuring cosmic expansion. The enormous gravitational fields of superstructures can alter these motions, leading to discrepancies in Hubble constant calculations.

Such effects underscore the need for precise cosmological models. Current simulations based on the Lambda Cold Dark Matter (ΛCDM) model predict the existence of superstructures like Quipu, reinforcing the validity of this cosmological framework. However, the influence of these structures on observational data means that scientists must refine their techniques to achieve more accurate measurements.

Despite their staggering size, superstructures like Quipu are not permanent fixtures of the cosmos. Over billions of years, as the universe continues to expand, these immense formations will gradually break apart into smaller structures. Individual galaxy clusters will drift away from one another, erasing the large-scale patterns observed today.

"In the future cosmic evolution, these superstructures are bound to break up into several collapsing units," the researchers noted. "They are thus transient configurations. But at present, they are special physical entities with characteristic properties and special cosmic environments deserving special attention."

The discovery of Quipu and its counterparts marks a turning point in our understanding of cosmic architecture. These structures serve as laboratories for studying galaxy evolution, large-scale gravitational interactions, and the effects of dark matter on cosmic formation.

By unraveling the mysteries of these vast formations, astronomers edge closer to comprehending the fundamental forces that shape the universe.

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