The study is based on data collected by the star hunter Gaia, from the European Space Agency (ESA). To shape the Milky Way, according to the authors of the research, was one of its neighbors, the dwarf galaxy of Sagittarius. Thanks to Gaia, astronomers have made an estimate of the brightness of over 24 million stars, inside a sphere with a diameter of 6,500 light years around the Sun. And, comparing these data with stellar models, they managed to reconstruct the evolutionary history of the Milky Way with a precision never achieved before.
Interaction sequence between the Milky Way and the nearby dwarf galaxy of Sagittarius (source: ESA)
For Cassisi, “the study shows that the Milky Way experienced a very violent star formation process about 13 billion years ago, the intensity of which has gradually decreased over time. We have identified – clarified the scholar – some intense star formation events. The first would have occurred about 5-6 billion years ago, followed by other events, 2 billion and 1 billion years ago, respectively. To get to the bottom – added Cassisi – just 100 million years old “.
Experts have, in fact, explained that the Milky Way is literally cannibalizing the dwarf galaxy of Sagittarius. A process, they stress, that actually started 5-6 billion years ago, when Sagittarius first approached the Milky Way. The Sun itself, the authors of the study point out, was in fact formed about 4.6 billion years ago and could be one of the stars born due to the first interaction between the Milky Way and Sagittarius.
An interaction that repeated itself 2 billion and 1 billion years ago. And that continues today, so much so that astronomers define the Sagittarius galaxy “one of the main architects in determining the morphology of the Milky Way”.