Physicists from MIT have made a remarkable breakthrough that could transform our grasp of the Milky Way’s structure, especially in terms of its gravitational heart and the puzzling dark matter. Their comprehensive analysis of data from the Gaia space observatory and the APOGEE ground survey has set the stage for vigorous discussions among astronomers.
The research centered on the “circular velocity” of stars, or the speed at which each star moves in the galactic plane, depending on how far it is from the galaxy’s nucleus. By charting these speeds against their distances, the team developed a rotation curve, which is key to understanding how both visible and invisible matter is distributed within a galaxy.
An Unexpected Discovery
MIT’s Lina Necib was taken aback by the rotation curve’s behavior. Instead of the expected gradual decrease, it stayed flat over a distance before sharply falling. This suggests that the galaxy’s outer stars are moving slower than previously thought.
This peculiar motion prompted the team to rethink how dark matter is spread out in our galaxy. They surmised that there might be less dark matter in the core of the Milky Way than once assumed. “This finding challenges other studies,” Necib remarked, noting that resolving this contradiction is crucial to forming a unified depiction of the Milky Way.
Honoring Vera Rubin’s Legacy
This research builds upon the groundbreaking work of astronomer Vera Rubin in the 1970s. Rubin first noticed that galaxies’ rotation could not be explained by visible matter alone, hinting at the existence of dark matter that affects the motion of distant stars. Rubin’s seminal work laid the foundation for the discovery of dark matter, a mysterious substance that appears to dominate over visible matter in the universe.
The Challenge of Mapping Our Galaxy
Calculating the Milky Way’s rotation curve is difficult because we are inside the galaxy, as scientist Xiaowei Ou points out. In 2019, MIT’s Anna-Christina Eilers took on the task of plotting this curve using Gaia’s data, which initially showed a flat but slightly declining curve, suggesting a dense dark matter core.
More recent Gaia data, reaching farther from the galactic center, along with APOGEE’s detailed information on stars, provided fresh perspectives. The team modeled circular velocity, and their findings indicated a larger-than-expected drop in the outer galaxy, contradicting previous assumptions about dark matter distribution.
A New Chapter in Cosmic Research
This study revises our perception of the Milky Way. By leveraging cutting-edge tools and methods, the researchers uncovered an unexpected deceleration of outer stars, prompting a reexamination of dark matter’s role in the galaxy. Their work exemplifies the evolving nature of space research, opening new inquiries and reshaping our cosmic models as the quest to demystify dark matter and the universe continues.
