The Chinese astronomers have recently discovered that the warp in the Milky Way’s spiral disk is precessing backward due to the influence of the dark matter halo surrounding our galaxy. This backward precession is a result of the enormous mass of dark matter exerting a torque on the disk, causing it to change alignment with the rest of the galaxy over time.
The warp in the Milky Way is not a fixed structure, but rather a dynamic one that moves and precesses around the galaxy. Previous attempts to measure the rate of precession using old giant stars as tracers have been imprecise. However, a new study led by Yang Huang of the Chinese Academy of Sciences used Cepheid variable stars as tracers to make a more accurate measurement of the warp’s precession.
Cepheid variables are pulsating massive stars with periods of pulsation linked to their intrinsic brightness. By studying these stars, researchers were able to map the warp of the Milky Way at different points in time over the past 200 million years. The motion picture method used by the researchers showed that the warp is precessing in a retrograde fashion, contrary to previous beliefs, at a rate of 2 kilometers per second for every kiloparsec of space.
Furthermore, the researchers found that the precession rate decreases with distance from the galactic center, indicating that the dark matter halo exerting the torque is oblate or flattened in shape. This discovery provides valuable insights into the formation history of the Milky Way galaxy and the nature of dark matter.
The results of this study were published in a paper in Nature Astronomy on June 27, shedding new light on the dynamics of the Milky Way’s warp and its interaction with dark matter. This research not only enhances our understanding of our own galaxy but also contributes to the broader field of astrophysics and cosmology.
Overall, this study highlights the importance of using advanced techniques and accurate tracers to unravel the mysteries of the universe. By combining observational data with theoretical models, scientists can continue to explore the complexities of galaxies, dark matter, and the evolution of the cosmos.
