The Milky Way’s Warp and Twisted Shape Explained by Tilted Dark Halo
In a new study, scientists have discovered that a misaligned dark halo could be the cause of the warped and twisted shape of the Milky Way. The dark halo is a large mass of dark matter that envelops and permeates our galaxy. These findings provide valuable insights into the evolutionary history of the Milky Way.
The research team, led by astrophysicist Jiwon Jesse Han of the Harvard & Smithsonian Center for Astrophysics (CfA), explains that a dark halo tilted in the same direction as the stellar halo can induce a warp and flare in the galactic disk. By comparing this model to observational data, they found that the misalignment of the dark halo and the disk offers clues about the galaxy’s formation history and represents a significant step in understanding its potential dynamics.
Due to living within the galaxy itself, it has been challenging for astronomers to discern its shape. However, the Gaia space telescope has provided us with high-precision measurements of stellar positions and velocities in the Milky Way, allowing for a detailed mapping of its wonky structure.
Prior to this study, astronomers had uncovered evidence of a warp and flare in the outskirts of the galaxy but were uncertain of the cause. While past explanations suggested an interaction with another galaxy, none could account for both the warp and flare. However, recent discoveries by Han’s team indicated that the halo of stars surrounding the Milky Way was also misaligned.
Performing simulations and modeling, the team concluded that a tilted dark halo explains the observed shape of the Milky Way. When they tilted the dark halo by 25 degrees relative to the galactic disk, the galaxy’s outer regions warped and flared, consistent with the Gaia observations.
While a galactic interaction is likely to have occurred, the simulation results suggest that it was in the past rather than an ongoing event. Additionally, the researchers found that after a collision with another galaxy, the dark halo’s tilt slowly returns to its normal orientation. The researchers speculate that the tilt of the Milky Way’s dark halo has decreased from a higher value in the past to its current tilt of approximately 25 degrees.
This study provides a more comprehensive understanding of the Milky Way’s shape and offers insights into the complex interplay between dark matter and visible matter in galaxies. The research has been published in Nature Astronomy.
Definitions:
– Dark halo: A large mass of dark matter that surrounds galaxies and interacts gravitationally with normal matter.
– Galactic disk: The flattened, rotating component of a galaxy that contains stars, gas, and dust.
– Dark matter: A type of matter that does not interact with light or other electromagnetic radiation and thus cannot be observed directly. It is thought to make up a significant portion of the mass of the universe.
Sources:
– Original article: “Misaligned dark halo explains the Milky Way’s warped disk” – Nature Astronomy
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