A team of scientists led by researchers from the Max Planck Institute for Extraterrestrial Physics and the Max Planck Institute for Physics, working with colleagues in Spain and South Africa, discovered the universe’s greatest superstructure that has ever been precisely characterized. The discovery was made while mapping the surrounding galaxy with galaxy clusters detected during the ROSAT X-ray satellite’s sky survey.
This snapshot from the Euclid space telescope shows about a thousand galaxies that form a single galaxy cluster, the Perseus Cluster. Taken together, many similar clusters form the largest structures in the universe, which resemble a network, with the galaxy clusters sitting in the nodes. Image Credit: ESA/Euclid/Euclid Consortium/NASA, Bildbearbeitung durch J.-C. Cuillandre, G. Anselmi; CC BY-SA 3.0 IGO
The new structure, which is primarily made up of dark matter, is the largest known structure to date, measuring over 1.4 billion lightyears.
The universe appears nearly homogeneous when averaged over very large volumes. It is characterized by voids and superclusters of matter condensations on scales smaller than around a billion light-years and in the cosmic neighborhood. Accurate understanding of these structures is crucial for cosmological studies and serves as the primary driving force behind charting the surrounding Universe.
If you look at the distribution of the galaxy clusters in the sky in a spherical shell with a distance of 416 to 826 million light-years, you immediately notice a huge structure that stretches from high northern latitudes to almost the southern end of the sky.
Hans Böhringer, Professor, Max Planck Institute for Extraterrestrial Physics
It is approximately 1.4 billion light years long, composed of 68 clusters of galaxies, and has an estimated total mass of 2.4 1017 solar masses. This surpasses the size record of any cosmic structure measured with accuracy. For example, the "Sloan Great Wall," previously the largest known structure, spans over 1.1 billion light-years.
An ATLAS of Galaxy Clusters
The team employed a nearly comprehensive atlas of galaxy clusters in the local universe to undertake their research.
The catalogue was created with the help of the ROSAT X-ray satellite, built by Max Planck Institute for extraterrestrial Physics. In 1990, the satellite mapped the entire sky using a high-resolution X-ray telescope for the first time.
Joachim Trümper, ROSAT Project Leader and Emeritus Director, Max Planck Institute for Extraterrestrial Physics
Researchers sought to locate the galaxy clusters more accurately and calculate their distances in the ensuing decades. This produced a three-dimensional representation of their distribution, where the clusters of galaxies accurately depict the structure of the universe’s large-scale matter distribution, akin to how lighthouses depict a coastline. Up to a billion light-years out, the entire cosmic volume is covered by the catalog. The new structure appears to be significantly larger than any existing structure in this area.
Importance for Science: Cosmography and Cosmology
This discovery is critical not only to map the Universe, but also for various cosmological observations. The researchers demonstrated how the presence of these structures influences the measurement of the Hubble constant and microwave background. The cosmic background radiation was formed shortly after the Big Bang and provides significant information about the structure and evolution of the cosmos. The Hubble constant indicates the universe's current expansion rate.
Even if these are only corrections of a few percent, they become increasingly important as the accuracy of cosmological observations increases.
Gayoung Chon, Lecturer, University of Munich
The scientists named their extraordinary discovery “Quipu,” which is derived from the Inca language. The Incas employed strings with knots for bookkeeping and letters. The superstructure resembles this old script, appearing as a long fiber with side strands braided in it. The scientists also selected the name because most of the galaxy cluster distance measurements were conducted at the European Southern Observatory in Chile.