US, WASHINGTON (NEWS OBSERVATORY) — Astrophysicists are trying to find an explanation for what is happening on the outskirts of our galaxy.
According to a study published in the journal Nature Astronomy , something unknown affects the edge of the Milky Way, causing a “galactic skew” of its outer edges.
The Milky Way contains approximately 250 billion stars that cluster in spiral arms and revolve around a supermassive black hole located in the center of the galaxy. But astronomers are aware of other dynamics occurring in the far reaches of the Milky Way, where the galactic disk is bent and deformed under the influence of phenomena that are still unknown to scientists.
To shed light on this riddle, a team of researchers led by Eloise Poggio, an astrophysicist at the Italian National Institute of Astrophysics in Turin, studied the movements of 12 million stars in excess of 15.5 magnitude observed by the Gaia Space Telescope of the European Space Agency.
“We measured the strain rate by comparing the data with our models. Based on the obtained speed, one full revolution of the curvature around the center of the Milky Way takes 600-700 million years. This is much faster than we expected, based on the forecasts of other models,” Eloise Poggio.
The proposed explanations for the deformation include the influence of intergalactic magnetic fields, the asymmetry of a galactic halo from dark matter, or the absorption of another galaxy in the past.
However, the researchers note that the data obtained are in favor of a scenario of temporary disturbance of the outer regions of the Milky Way disk caused by interaction with a satellite galaxy. It may be a dwarf elliptical galaxy in Sagittarius, but scientists still can not confirm this fact with confidence.
“The direction and magnitude of the curvature precession rate favors the scenario according to which it is the result of a recent or ongoing collision with a satellite galaxy, and not a relic of the galaxy’s ancient history. Additional observations and studies will be required to confirm that the deformation is mainly caused by satellite galaxies. Nevertheless, our results show that external forces from interacting satellite galaxies play an important and constant role in the formation of the outer disk of the Milky Way,” the study says.
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