MIT physicists have made a surprising discovery about the motion of stars in the Milky Way, indicating a potential reduction in the amount of dark matter at the galaxy’s core. By examining the speed of stars across the Milky Way, researchers found that those on the outer edges move more slowly than expected compared to stars closer to the center. This unexpected finding challenges previous estimations of the galactic core’s mass and dark matter content.
The study, based on data from Gaia and APOGEE instruments, involved analyzing Gaia’s measurements of over 33,000 stars throughout the galaxy. The researchers determined each star’s “circular velocity” based on its distance from the galactic center, plotting a rotation curve that illustrates how matter rotates at various distances. Contrary to expectations, the curve remained flat until a certain distance, where stars unexpectedly slowed down.
To explain this slowdown, the team translated the rotation curve into a dark matter distribution map, revealing a lighter galactic core than anticipated. The implication is that the Milky Way’s center may have less density and fewer dark matter particles than previously thought. The researchers acknowledge that this result contradicts other measurements and express excitement about unraveling the mysteries surrounding the galaxy’s equilibrium and hidden masses beyond its disk in future high-resolution simulations.
The findings, reported in the Monthly Notices of the Royal Society Journal, challenge the current understanding of the Milky Way’s structure and were derived from a combination of Gaia’s precise measurements and APOGEE’s ground-based survey data. The researchers, including MIT physicists Xiaowei Ou, Lina Necib, Anna-Christina Eilers, and Anna Frebel, believe that further investigations and simulations will be crucial to gaining a comprehensive understanding of the Milky Way’s dynamics. The study received partial funding from the National Science Foundation.
