Dark matter is central because it does not emit light, so researchers track it by watching how gravity tugs on visible galaxies.<\/p>\n\n\n\n
Read More: Scientists discover that the Milky Way may be floating on a dark-matter sheet millions of light-years wide, changing the map of our galaxy\u2019s hidden support<\/a><\/h3>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\nThe research was led by Ewoud Wempe with Simon D. M. White, Amina Helmi, Guilhem Lavaux, and Jens Jasche, and Helmi said, “Based purely on the motions of galaxies, we can determine a mass distribution.” <\/p>\n\n\n\n
Their institutions include the Kapteyn Astronomical Institute at the University of Groningen, the Max-Planck-Institut f\u00fcr Astrophysik, the Institut d\u2019Astrophysique de Paris at CNRS and Sorbonne Universit\u00e9, and the Oskar Klein Centre at Stockholm University.<\/p>\n\n\n\n
Why the nearby universe has looked oddly calm<\/h2>\n\n\n\n
Almost a century ago, Edwin Hubble showed that distant galaxies recede as space expands<\/a>. Yet Andromeda is coming toward us at about 62 miles per second, close to 224,000 miles per hour. That approach implies the Local Group contains far more mass than its visible stars can explain.<\/p>\n\n\n\nNow here is the odd part. Many galaxies just outside the Local Group still move away in a smooth \u201cHubble flow,\u201d meaning they mostly follow expansion with only small extra motions. Older spherical models struggled to match that quietness unless they assumed surprisingly little mass beyond the two main galaxies.<\/p>\n\n\n\n
This contradiction goes back generations. A 1959 timing argument paper by Franz Kahn and Lodewijk Woltjer used the Milky Way-Andromeda motion to infer a huge amount of unseen mass, an early clue pointing to dark matter. The record for that work is available at ADS<\/a>.<\/p>\n\n\n\n![\"Simulation](\"https:\/\/www.ecoticias.com\/en\/wp-content\/uploads\/2026\/05\/local-group-dark-matter-plane-simulation.jpg\" "\\"\\"")
Researchers used cosmological simulations to model a giant dark matter sheet surrounding the Local Group and nearby galaxies.<\/figcaption><\/figure>\n\n\n\nHow scientists built \u201cvirtual twins\u201d of our neighborhood<\/h2>\n\n\n\n
To tackle the puzzle, the team relied on a simulation approach called Bayesian Origin Reconstruction from Galaxies, or BORG. In plain terms, it starts with likely conditions in the early universe and evolves them forward, while using today\u2019s observations to keep the outcome realistic. It explores many plausible cosmic histories.<\/p>\n\n\n\n
From this framework, the researchers ran 169 independent, high-resolution simulations of a region about 130 million light-years across. Each simulation was required to produce Milky Way<\/a> and Andromeda-like galaxies with the right separation and relative motion. <\/p>\n\n\n\n\n\n\nRead More: For years they were believed to be the last mammoth bones, until scientists discovered they were whales found 400 kilometers from the coast<\/a><\/h3>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\nThe simulations also had to match the distances and recession speeds of 31 nearby galaxies out to roughly 13 million light-years.<\/p>\n\n\n\n
When they compared those virtual twins, a flattened mass distribution kept showing up. The data repeatedly favored a plane, not a sphere, plus void-like regions above and below. A plain-language summary of the result is posted at Rug<\/a>.<\/p>\n\n\n\nWhat the simulations say the sheet looks like<\/h2>\n\n\n\n
In the best-fitting picture, the mass is concentrated in a sheet that extends past about 30 million light-years from the Local Group. The central part of the sheet is roughly 5 million light-years thick, thin on cosmic scales. Near the middle of the sheet, the average matter density is about double the cosmic average.<\/p>\n\n\n\n
Move above or below the plane and the density drops sharply, down to roughly one quarter to one third of the average. The sheet\u2019s surface density also rises farther from the Local Group, meaning there is more mass spread across each patch of the plane at larger distances. The paper itself can be read at Nature<\/a>.<\/p>\n\n\n\nHow a \u201cflat\u201d universe changes the pull of gravity<\/h2>\n\n\n\n
Gravity in a plane behaves differently than gravity in a sphere. In a spherical setup, extra mass mostly adds an inward pull toward the center, which should slow or reverse the outward motion of nearby galaxies. In a sheet, mass spread along the same plane can tug in ways that partly counteract the Local Group\u2019s inward pull.<\/p>\n\n\n\n
The study\u2019s velocity maps reflect that. Within the sheet, the strongest pull inward is limited to the inner region within about 8 million light-years, and farther out the extra motions can point away from the group. Above and below the sheet, the simulations predict much stronger flow toward the plane, reaching around 62 miles per second in some regions.<\/p>\n\n\n\n
\n\n\nRead More: Scientists propose building a wall more than 80 kilometers long to slow the Doomsday Glacier, an idea that sounds impossible because the alternative may be worse<\/a><\/h3>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\nSo why have astronomers not seen that dramatic flow already? The paper argues there are few good \u201ctracer\u201d galaxies in those directions, meaning galaxies with well-measured distances and speeds, so the pattern is easy to miss. A separate explainer of the historical puzzle is at su.se<\/a>.<\/strong><\/p>\n\n\n\nWhat this means for dark matter and what comes next<\/h2>\n\n\n\n
For cosmologists, the main payoff is a cleaner fit. A flattened dark matter sheet can reconcile Local Group mass estimates with the calm local Hubble flow, without abandoning the standard Lambda Cold Dark Matter model<\/a>, the leading picture of how structure forms in the universe. It is a reminder that local geometry can matter as much as total mass.<\/p>\n\n\n\nThe result also sets up practical next steps. If future surveys measure more galaxy distances and speeds above and below the plane, the team expects a clearer signature of flow toward the sheet. That prediction is testable, which is what you want from a model like this.<\/p>\n\n\n\n
The preprint version of the new paper is also published on Arxiv<\/em><\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"Galaxies are not sprinkled evenly through space. They clump in clusters, stretch into filaments, and leave behind huge \u201cvoids.\u201d A … <\/p>\n
Now here is the odd part. Many galaxies just outside the Local Group still move away in a smooth \u201cHubble flow,\u201d meaning they mostly follow expansion with only small extra motions. Older spherical models struggled to match that quietness unless they assumed surprisingly little mass beyond the two main galaxies.<\/p>\n\n\n\n
This contradiction goes back generations. A 1959 timing argument paper by Franz Kahn and Lodewijk Woltjer used the Milky Way-Andromeda motion to infer a huge amount of unseen mass, an early clue pointing to dark matter. The record for that work is available at ADS<\/a>.<\/p>\n\n\n\n To tackle the puzzle, the team relied on a simulation approach called Bayesian Origin Reconstruction from Galaxies, or BORG. In plain terms, it starts with likely conditions in the early universe and evolves them forward, while using today\u2019s observations to keep the outcome realistic. It explores many plausible cosmic histories.<\/p>\n\n\n\n From this framework, the researchers ran 169 independent, high-resolution simulations of a region about 130 million light-years across. Each simulation was required to produce Milky Way<\/a> and Andromeda-like galaxies with the right separation and relative motion. <\/p>\n\n\n\n The simulations also had to match the distances and recession speeds of 31 nearby galaxies out to roughly 13 million light-years.<\/p>\n\n\n\n When they compared those virtual twins, a flattened mass distribution kept showing up. The data repeatedly favored a plane, not a sphere, plus void-like regions above and below. A plain-language summary of the result is posted at Rug<\/a>.<\/p>\n\n\n\n In the best-fitting picture, the mass is concentrated in a sheet that extends past about 30 million light-years from the Local Group. The central part of the sheet is roughly 5 million light-years thick, thin on cosmic scales. Near the middle of the sheet, the average matter density is about double the cosmic average.<\/p>\n\n\n\n Move above or below the plane and the density drops sharply, down to roughly one quarter to one third of the average. The sheet\u2019s surface density also rises farther from the Local Group, meaning there is more mass spread across each patch of the plane at larger distances. The paper itself can be read at Nature<\/a>.<\/p>\n\n\n\n Gravity in a plane behaves differently than gravity in a sphere. In a spherical setup, extra mass mostly adds an inward pull toward the center, which should slow or reverse the outward motion of nearby galaxies. In a sheet, mass spread along the same plane can tug in ways that partly counteract the Local Group\u2019s inward pull.<\/p>\n\n\n\n The study\u2019s velocity maps reflect that. Within the sheet, the strongest pull inward is limited to the inner region within about 8 million light-years, and farther out the extra motions can point away from the group. Above and below the sheet, the simulations predict much stronger flow toward the plane, reaching around 62 miles per second in some regions.<\/p>\n\n\n\n So why have astronomers not seen that dramatic flow already? The paper argues there are few good \u201ctracer\u201d galaxies in those directions, meaning galaxies with well-measured distances and speeds, so the pattern is easy to miss. A separate explainer of the historical puzzle is at su.se<\/a>.<\/strong><\/p>\n\n\n\n For cosmologists, the main payoff is a cleaner fit. A flattened dark matter sheet can reconcile Local Group mass estimates with the calm local Hubble flow, without abandoning the standard Lambda Cold Dark Matter model<\/a>, the leading picture of how structure forms in the universe. It is a reminder that local geometry can matter as much as total mass.<\/p>\n\n\n\n The result also sets up practical next steps. If future surveys measure more galaxy distances and speeds above and below the plane, the team expects a clearer signature of flow toward the sheet. That prediction is testable, which is what you want from a model like this.<\/p>\n\n\n\n The preprint version of the new paper is also published on Arxiv<\/em><\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":" Galaxies are not sprinkled evenly through space. They clump in clusters, stretch into filaments, and leave behind huge \u201cvoids.\u201d A … <\/p>\nHow scientists built \u201cvirtual twins\u201d of our neighborhood<\/h2>\n\n\n\n
Read More: For years they were believed to be the last mammoth bones, until scientists discovered they were whales found 400 kilometers from the coast<\/a><\/h3>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\n
What the simulations say the sheet looks like<\/h2>\n\n\n\n
How a \u201cflat\u201d universe changes the pull of gravity<\/h2>\n\n\n\n
Read More: Scientists propose building a wall more than 80 kilometers long to slow the Doomsday Glacier, an idea that sounds impossible because the alternative may be worse<\/a><\/h3>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\n
What this means for dark matter and what comes next<\/h2>\n\n\n\n