The Milky Way’s center may contain less dark matter than previously thought

Star velocities at the edge of the Milky Way reveal questions about dark matter density at the galaxy’s center Stars at the edge of the Milky Way are moving more slowly than previously thought. A team of physicists from the Massachusetts Institute of Technology (MIT) discovered this feature by examining data obtained with the Gaia space telescope and his APOGEE instrument on the ground. During the study, the physicist analyzed information about his more than 33,000 stars in the Milky Way galaxy, covering every remote corner of the galaxy. They measured the rotational speed of these stars and found that these stars at the edge of the galaxy were moving slightly slower than expected.

The researchers converted this data into a model of the distribution of dark matter. Dark matter is disadvantageous for observation because it does not emit light and only interacts with visible matter through gravitational interactions. However, it does affect the movement of the stars. This result suggests that the Milky Way core contains less dark matter than previously thought. This has important implications for ideas about the distribution of dark matter, as the presence of dark matter is believed to be an important factor in maintaining galaxy stability and explaining the observed rotational speed of galaxies. affect. If the hypothesis about a lighter core of the Milky Way is confirmed, it may require a revision of our thinking about galactic dynamics. Observing the rotational speed of galaxies is one of the important aspects of astronomy. In the 1970s, astronomer Vera Rubin realized that the rotational speed of galaxies could not be explained by visible matter alone. The rotational speed of the stars orbiting the center of the galaxy remains constant along the entire length of the galaxy, indicating the presence of additional invisible matter that influences the motion of the stars. Vera Rubin’s research provided some of the first convincing evidence for the existence of dark matter, a component thought to make up the majority of all matter in the universe. Later, astronomers found similar rotation curves in distant galaxies, supporting speculation about dark matter. But only recently have astronomers begun to use stellar data to study and record our galaxy’s rotation curve. In 2019, Anna Christina Eilers, a physics student teaching at MIT, became interested in studying the rotation curve of the Milky Way galaxy. It used previous data collected and published by the Gaia telescope, which collected statistics on stars up to 25 kiloparsecs (about 81,000 light-years) away from the galactic center.

When analyzing this data, Eilers found that, like other distant galaxies, the Milky Way’s rotation curve appears flat, slightly dimpled at the edges. This suggests that there is dense dark matter at the center of the galaxy. But the new set of data from the satellite added stars up to 30 kiloparsecs, or about 100,000 light-years away, from the galaxy’s center. Eilers’ team acquired new Gaia data and supplemented it with measurements from APOGEE (Apache Point Galactic Observatory). APOGEE analyzes the properties of more than 700,000 stars in the Milky Way galaxy, including their brightness, temperature, and composition. Using this data, the team determined the exact distances of his more than 33,000 stars and created a 3D map showing the locations of these stars, which are within 30 kiloparsecs of the Milky Way. They then fed this map into a rotational velocity model, which took into account the distribution of other stars in the galaxy and predicted the velocity of each individual star. Based on this, scientists created an updated rotation curve for the Milky Way and plotted the velocity and distance of each star on a graph. “Here we encountered an unusual result,” says research team member Lina Nekib. Instead of the small decline expected in the suburbs, the team found a larger decline. This suggests that the outer star is moving even more slowly than expected. By converting rotation curves into the amount of dark matter contained in galaxies, researchers found that the Milky Way’s center may have less dark matter than previously thought. “This result contradicts previous observations. A closer look at our results raises important implications: This could indicate the presence of more hidden mass outside the galactic disk, or Or it could lead to a rethinking of the balance of galaxies. To find answers to these questions, we want to look to high-resolution simulations of galaxies similar to the Milky Way,” said Nekib. say.