Scientists recently announced that they have confirmed the "most reliably measured and largest cosmic superstructure" in the observable universe. This behemoth, woven together by galaxies, galaxy clusters and dark matter, is named "Quipu". Its scale is so large that it stretches about 1.4 billion light-years along the cosmic space, officially breaking the record for the largest structure in the known universe.
The research was led by the Max Planck Institute for Extraterrestrial Physics and the Max Planck Institute for Physics in Germany, and was completed in conjunction with scientists from Spain and South Africa. By analyzing the distribution map of galaxy clusters across the sky drawn by the ROSAT X-ray satellite, they gradually locked and reconstructed the three-dimensional distribution of this superstructure.
Project leader Hans Berlinger pointed out that if you observe the distribution of galaxy clusters in a spherical shell region about 416 million to 826 million light years away from the Earth, a huge structure extending from the high latitudes of the northern sky to close to the edge of the southern sky will be particularly eye-catching. This is Quipu.
This structure is composed of 68 huge galaxy clusters, with a total mass of approximately 2×10¹⁷ solar masses. Its length exceeds 400 megaparsecs (approximately 1.4 billion light-years), and its volume significantly exceeds the previously famous "Sloan Great Wall" (approximately 1.1 billion light-years).
This discovery is inseparable from the basic work of the ROSAT satellite. As the first satellite to complete an all-sky X-ray survey, ROSAT has scanned the entire sky with a high-resolution X-ray telescope since 1990, recording the high-energy radiation emitted by the hot gas between galaxy clusters, and establishing a detailed catalog of galaxy clusters for scientists.
As major observatories continued to measure the distances of these galaxy clusters in the following decades, the research team was able to construct a more accurate three-dimensional distribution map of matter. It was in such a "cosmic map" that Quipu was identified as the largest superstructure known so far within a billion light-years from the Earth.
The research paper emphasizes that in order to accurately determine key cosmological parameters such as the expansion rate, matter density and geometry of the universe, the impact of local large-scale structures on observational data must be fully considered.
These effects include subtle modifications of the cosmic microwave background radiation by large-scale gravitational fields, bending of light paths through gravitational lensing, and shifts in Hubble constant measurements caused by "overall flow" caused by large-scale matter distribution, the latter of which can be produced by huge mass concentrations up to 250 megaparsecs apart.
In the latest work, the team conducted the first systematic assessment of large-scale structures throughout the sky in the range of 130 to 250 megaparsecs. Among the five most significant superstructures selected, Quipu ranked first in both length and mass.
Research shows that this type of superstructure is not an extremely rare "special case": they accommodate about 45% of galaxy clusters, 30% of galaxies, and about a quarter of the matter, but only occupy about 13% of the volume of the universe. They are an extremely important component of the large-scale structure of the universe.
Observations also show that the spatial density of galaxies near these superstructures is significantly higher than in the environment of isolated galaxy clusters, suggesting that large-scale gravitational networks have an important influence on the formation and evolution of galaxies.
At the same time, numerical simulations based on the current mainstream Λ-CDM (Lambda cold dark matter) cosmological model also gave a large-scale structure similar to Quipu, providing theoretical support for this observation, showing that this discovery is highly consistent with the standard cosmological framework.
Scientists point out that such a huge material structure should leave traces of the so-called "integrated Sachs-Whorf effect" in the cosmic microwave background, which is the subtle change in energy of photons as they pass through a gravitational potential well that evolves over time.
The research team searched for this signal in the data of the Planck satellite and indeed found signs that were consistent with the intensity expected by theory. However, the statistical significance was not enough to completely rule out the possibility of random fluctuations, so subsequent more accurate data verification is still needed.
Jon, who participated in the research, emphasized that even if these corrections only bring a deviation of a few percentage points on the surface, as the accuracy of cosmological observations continues to improve, they will become more and more critical in the future, related to our fine characterization of the overall nature of the universe.
In other words, to understand the universe at an accuracy level of "a few percent", the existence and distribution of large-scale superstructures can no longer be simply ignored.
The name "Quipu" comes from the knotting system used by the Inca civilization to record information - "Knotting", because the shape of the superstructure in space resembles a main fiber with branching strings.
The name also pays tribute to the European Southern Observatory in Chile, where many key distance measurements were completed, and the Inca knotted rope artifacts displayed in the local museum also build a historical and cultural bridge for this cosmic discovery to some extent.
Researchers pointed out that this discovery not only provides a new "ruler" for us to map the distribution of matter in the universe, but also provides a unique experimental field for testing cosmological models and studying the formation and evolution of galaxies in different environments.
Superstructures like Quipu show that the largest "cosmic web" in the universe is not only a background stage, but also has a substantial impact on mankind's most sophisticated cosmic measurements today, thus shaping our understanding of the fate and origin of the universe.