An international team of astronomers has found evidence that the Laniakea supercluster, which contains the Milky Way galaxy, could be a part of the Shapley concentration, a massive structure ten times the size of Laniakea, which suggests our cosmic neighborhood is much larger than previously thought.
A decade ago, this team — led by astronomers at the University of Hawaiʻi Institute for Astronomy, already concluded that our galaxy resides within a massive basin of attraction called Laniākea, which is presently 500 million light-years in diameter. Lanikea is basically an immense supercluster of galaxies, including our own.
However, new data suggests that this understanding may only scratch the surface.
There is now a 60% probability that we are part of an even grander structure, potentially 10 times larger in volume, centered on the Shapley concentration — an immense concentration of galaxies and dark matter with a strong gravitational pull on everything nearby. The region also described as the “basin of attraction.”
While these massive superclusters cover enormous portions of the universe, the study focuses on the movements and interactions of galaxies within and between these structures, including the Milky Way’s local basin of attraction, Laniakea.
“Our universe is like a giant web, with galaxies lying along filaments and clustering at nodes where gravitational forces pull them together,” said UH Astronomer R. Brent Tully, one of the study’s lead researchers.
“Just as water flows within watersheds, galaxies flow within cosmic basins of attraction. The discovery of these larger basins could fundamentally change our understanding of cosmic structure.”
Astronomers have been researching the Shapley concentration since its discovery by Harlow Shapley in the 1930s. However, it is only now, thanks to more precise data and powerful algorithms, that scientists can refine their understanding of its size and significance.
The basis for this discovery stems from the ongoing attempt to map the universe’s most significant structures. Galaxies are not randomly spread over space; they cluster and supercluster, forming a complicated web-like structure due to gravity’s pull.
Scientists examine these motions to understand how galaxies move within basins of attraction. The discovery that Laniakea may be part of the much bigger Shapley Concentration is essential because it sheds new light on the gravitational forces forming the universe.
The discovery also calls into question the magnitude and scope of these gigantic structures and whether current cosmological models account entirely for their existence.
The method of mapping these structures is complicated. It entails measuring galaxy redshifts (the shift in light wavelength caused by their movement) and unusual velocities (the movement of galaxies relative to the overall expansion of the universe).
Tully’s team — also known as CosmicFlows — employed advanced algorithms like the Hamiltonian Monte Carlo approach, to examine the movements of 56 000 galaxies in their CosmicFlows-4 data.
These observations enabled scientists to generate three-dimensional maps of galaxy movements and pinpoint areas where gravitational forces predominate. The Shapley concentration has a significant gravitational pull, which may affect the trajectory of the Milky Way galaxy and the bigger Laniakea supercluster.
Future studies will reveal more about the vast and interconnected universe as observations and data get more sophisticated.
“This discovery presents a challenge: our cosmic surveys may not yet be large enough to map the full extent of these immense basins,” said co-author of the study Ehsan Kourkchi. “We are still gazing through giant eyes, but even these eyes may not be big enough to capture the full picture of our universe.”
References:
1 Identification of basins of attraction in the local Universe – Valade, A., Libeskind, N.I., Pomarède, D. et al. – Nat Astron (2024) – September 27, 2024 –
2 UH astronomers: Our cosmic neighborhood may be 10x larger – University of Hawaii – September 27, 2024