“Basins of attraction” are the center of a new model of the universe, pushing forward our understanding of its vast structure. Led by Dr. Aurélien Valade, an international team of scientists, formulated the theory, forcing astrophysicists to rethink how the universe evolved.
To make sense of the universe, astrophysicists construct mathematical models, a group of equations that explain how the universe operates. Dr. Valade’s team based their work on an existing one called the Lambda Cold Dark Matter model. That’s the standard model most scientists use to understand the Big Bang. In it, a feature that became central to their work is the so-called “basins of attraction.”
Like a sink basin, with water rushing towards its central drain, a basin of attraction is an area of increased gravity. They grew with the universe. Gravity was unstable in some places as the universe expanded after the Big Bang. That instability leads to some points of exceptionally strong gravity, the basins of attraction. Today those points anchor the spinning galaxies of our universe.
The team combined the Lambda model with a huge data set covering 56,000 galaxies to perform their research. Their biggest issue was that collecting data about speed and distance over such vast areas can be challenging. They estimated that about 15% might be “noise,” or incorrect data. To smooth this out, they used the Hamilton Monte Carlo algorithm, often used by data scientists to correct data sets that may contain some inaccurate numbers. From these operations, they estimated the density and velocity fields of the objects they were looking at. Using the existing universe model helped alleviate some of the estimated 15% signal-to-noise ratios in the data, as distances are prone to relative error rates of around 20%.
The team’s main goal was to broaden the scientific understanding of the scale at which the universe operates. Before, it was accepted that the Milky Way Galaxy was just a part of the Laniakea Supercluster. Now, the team’s data points toward Laniakea being part of an even larger formation, the Shapley Basin of Attraction.
Data analysis identified further basins of attraction spread through the universe. The Sloan Great Wall is the largest, encompassing half a billion light years. It dwarfs Shapey, previously considered to be the most massive basin.
In conversation with The Debrief, Hoffman said, “The dominance of the Sloan Wall basin of attraction over the Shapley basin is truly surprising. All previous studies, including our own, suggested that Shapley is the main player.” The data serves to illuminate the gravitational evolution of the universe.
Studying cosmology from a vantage point on Earth is difficult because large structures deviate less from the cosmic background with distance. This limits understanding of the scale of the universe, as with distance, interesting features become murkier and murkier. Added to this distance is the universe’s randomness, limiting its predictability. To move forward, “our reconstruction of the present-day large-scale structure needs to accommodate that inherent randomness and also the observational uncertainties,” Hoffman said. “Our main challenge is to turn the current qualitative description of our local universe into a quantitative one and thereby to use it as a test on the standard model of cosmology.”
The paper “Identification of basins of attraction in the local Universe” was published in Nature Astronomy on September 27, 2024.
Ryan Whalen covers science and technology for The Debrief. He holds a BA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.