The Milky Way and our nearby galaxies, known as the Local Group, may be surrounded by a vast “sheet” of dark matter. Researchers have recently pointed this out in a study published in Nature Astronomy. This could explain why some galaxies seem to move in unusual ways, seemingly unaffected by gravity.
This mystery goes back to Edwin Hubble’s discovery about a century ago. He found that most galaxies are moving away from us, and the farther they are, the faster they appear to be moving. However, Andromeda, our closest major galaxy, is heading toward the Milky Way. This posed a puzzle, as Andromeda and the Milky Way are part of the Local Group, which should pull galaxies together via gravity.
To tackle this, scientists created a virtual version of the Local Group and other nearby galaxies. They modeled its evolution using data from the cosmic microwave background—the afterglow of the Big Bang. By comparing the simulated galaxies to actual observations, they discovered a close match, suggesting their simulation was accurate.
What did they find? The Local Group seems to sit within a massive sheet made of dark matter, an invisible substance making up about 85% of the universe’s mass. This proposed flat geometry of dark matter offers a solution to the movement of nearby galaxies. According to lead researcher Ewoud Wempe from the Kapteyn Institute in Groningen, the study is a groundbreaking step in understanding dark matter’s distribution and velocity within our Local Group.
This research aligns with how we think about the cosmos today but contrasts with older models that depicted dark matter as clumpy spheres. Instead, this sheet-like formation suggests that galaxies are being pulled outward by the mass at the edges of this sheet, while the void beyond it has no galaxies.
Understanding dark matter better not only sheds light on our local cosmic neighborhood but also contributes to our broader comprehension of the universe’s structure. As astronomers continue to explore these mysteries, we may uncover more fascinating insights about what lies beyond our sight.
For more information about dark matter, check out this report on its distribution across galaxies.
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Local Group, dark matter, nearby galaxies, Wempe
