How massive is the Milky Way?

Led by Ekta Patel, a fourth-year graduate at the University of Arizona, this study is the first of its kind to use 3D movements of satellite galaxies and to compare their angular momentum to a simulated universe , finally concluding the Milky Way. tipped the scales at 0.96 trillion times the mbad of the sun. Unlike previous studies that used the positions and velocities of satellite galaxies, this new study exploits the lack of net change between the two. As the angular momentum of a system remains constant over time, this new method allows researchers to remove some of the uncertainty that plagues other approaches, paving the way for more reliable results.

"Think of an artistic skater doing a spin," says Patel in a press release. "As she pulls in her arms, she turns faster, in other words, her speed changes, but her angular momentum stays the same throughout her act."

Presented at the 232nd American Astronomical Society in Denver, the study uses satellite galaxy data from the Hubble Space Telescope. In order to reach the estimate of $ 0.96 trillion solar mbad, the study compared the kinetic moments of nine satellite galaxies to those of a simulated universe of 20,000 galaxies, just like ours. This comparison made it possible to draw nine probability distributions – possible ranges of values ​​for the mbad of our galaxy – all of which made it possible to estimate 0.96 trillion solar mbades.

"Our method allows us to take advantage of measurements of the velocity of several satellite galaxies simultaneously to obtain a response to what the theory of cold dark matter would predict robustly for the Milky Way halo mbad" author Gurtina Besla in a press release ..

It is not uncommon for researchers to use information from satellite galaxies to measure the mbad of the Milky Way. As we are unable to see the entire galaxy, we rely on its interactions with neighboring galaxies. The Milky Way is the proud owner of at least 50 of these galaxies – called the local group – each comprising its own abundance of stars.

However, not everyone is well understood. With the exception of Magellan clouds, which are clearly visible to the naked eye, all other satellite galaxies are extremely difficult to detect, even with a telescope, making it difficult to determine their existence . The brightness of a satellite galaxy is often used to estimate its mbad, but the orbital motions are not always consistent with the results obtained with the previous method. To explain this imbalance between what we can detect and the invisible mbad of our universe, researchers have turned to the theory of dark matter and cold.

According to the theory, dark matter is composed of heavy and slow particles that represent about 85% of the matter of the universe. This type of dark matter interacts weakly with visible matter to form small tufts that are then joined together to form larger bodies.