Motion analysis of several groups of stars in the halo of the milky Way by a team of astronomers from Groningen University (the Netherlands), suggests that our Galaxy in the past has experienced at least five small and one large-scale clash. The results of the study presented in the journal Astrophysical Journal Letters.
The work is based on the second edition of the ESA satellite “Gaia”, which provided the astronomical community with accurate information about the position and movement of millions of stars.
“Our goal is to understand how evolved the milky Way. The generally accepted mechanism of evolution of galaxies is mergers of smaller structures, which form larger homes. However, the main issue is the size of the primary components: merges many small or a few large galaxies? And since most stars in the halo of the milky Way are considered to be remnants of such events, my colleagues and I focused on these objects”, – says Helmer Koppelman, lead author of the study.
Initially, scientists have identified information about the stars, located at a distance of 3000 light-years from the Sun, because they “Gaia” have gathered the most accurate information about position and movement. Then they filtered out the stars from the disk of the milky Way that are moving around the center of our Galaxy. As a result, astronomers remained a group of about 6000 of the stars residing in the halo.
Calculating their trajectory, Helmer Koppelman and his team were able to identify groups of stars with a common origin.
“We found five small clusters which, in our opinion, are the remains of the five events of the merger. In addition, we were able to identify one large cluster with a retrograde motion relative to the disc of the milky Way. This indicates merging with a large galaxy in the past, which, we believe, changed the structure of our Galaxy. As a result, we can say that the milky Way was formed by one large and several small mergers,” explains Helmer Koppelman.
Now astronomers are planning to explore the stars located at a distance of over 3000 light-years from the Sun to bring out more participants of the identified flows. Along with modeling the evolution of galaxies, the acquired data should provide exciting new hypotheses for the development of the milky Way.
Astronomers figured out how many of the galaxies is our milky Way
Nikolai Khizhnyak