A brand new look at the dwarf galaxies surrounding the Milky Way |  Urania

New research shows that most of the Milky Way’s galaxies may be destroyed after entering the galactic halo.

New research suggests that most of them are long-term Space galaxies for us milky way They may actually be destroyed once inserted Galaxy halo. Analyze the latest catalog from Gaia satelliteAn international team of scientists discovered this Dwarf galaxies It may be able to be unbalanced. This study raises important questions about… Standard cosmological modelespecially regarding its occurrence Dark matter In our immediate surroundings.

Dwarf galaxies around the Milky Way have long been thought to be ancient satellites that have been orbiting our galaxy for approximately 10 billion years. The existence of these galaxies requires huge amounts of dark matter, which protects them from the strong gravity of our galaxy. The observed differences in stellar velocities in these dwarf galaxies are presumed to be caused by dark matter.

The latest data from Gaia has provided a completely new picture of the properties of dwarf galaxies. By analyzing the orbital energy of objects based on the time of their entry into the Milky Way’s halo, a team of astronomers was able to estimate the history of our galaxy. They found that objects that arrived earlier, when the Milky Way was less massive, had lower orbital energies than those that arrived later. Interestingly, most dwarf galaxies have orbital energies much higher than those of dwarf galaxies Sagittarius dwarf galaxyWhich entered the corona about 5-6 billion years ago. This indicates that most dwarf galaxies appeared later, less than three billion years ago.

Recent discoveries suggest that dwarf galaxies close to our Galaxy come from outside the halo, as most dwarf galaxies contain large reservoirs of neutral gas. Gas-rich galaxies lost this gas as a result of their collision with hot gas present in the galactic corona. This process caused violent shocks and disturbances that completely changed the structure of dwarf galaxies. Previously, gas-rich dwarf galaxies were dominated by the rotation of gas and stars, but after the loss of gas, their gravity was balanced by the random motions of the remaining stars. This rapid process of gas loss means that the speed of stars in these galaxies is no longer balanced by the acceleration of gravity. The effects of gas loss and gravitational shocks resulting from galactic immersion explain the wide range of stellar velocities observed in dwarf galaxies.

One interesting finding of this study is the role of dark matter. First, the imbalance in dwarf galaxies in the Milky Way makes it impossible to accurately estimate their dynamical mass and dark matter content. Second, in previous theories, dark matter was thought to be a stabilizing factor in dwarf galaxies. However, in the case of imbalanced galaxies, recourse to dark matter becomes problematic. In fact, if the dwarf galaxy contains a large amount of dark matter, this presence would prevent it from turning into a galaxy with chaotic stellar motions, as observed.

The recently described discoveries about dwarf galaxies and their transformation into halos perfectly explain many of the observed features of these objects, especially the fact that they have stars located at great distances from the center. Their properties appear to be consistent with the absence of dark matter, in contrast to the previous view that dark matter dominates dwarf galaxies. Many questions arise, such as: Where are the many dark matter dwarf galaxies predicted by the standard cosmological model around the Milky Way? How can we infer the presence of dark matter in a dwarf galaxy when there is no equilibrium? What other observations can distinguish out-of-equilibrium dwarf galaxies from the classical picture of dark matter-dominated dwarf galaxies?

Test results have been published published w czasopiśmie Monthly Notices of the Royal Astronomical Society.

Agnieszka Novak

more information:

Source: AIP

Pictured: Dwarf galaxies around the Milky Way. Source: ESA/GAIA/DPAC

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