Astronomers from the Canary Islands Institute of Astrophysics in Spain used data from the Gaia Mission, launched in 2013, to understand how our galaxy and the Sun formed.
The Sagittarius dwarf galaxy played a crucial role in the evolution of the Milky Way, according to an article published last Monday (25) in the journal Nature Astronomy. The study also suggests that the galaxy was essential for the formation of the Sun.
The discovery is the result of research conducted by astronomers from the Canary Islands Institute of Astrophysics in Spain, who used data from the Gaia Mission, launched by the European Space Agency (ESA) in 2013. The team measured luminosity, position, movement, and chemical composition of a large number of individual stars in our galaxy to try to understand its evolution.
The astronomers discovered the intrinsic luminosity of 24 million stars over a distance of up to 6,500 light-years around the Sun. By comparing their light and color with that of previous models, scientists obtained the most detailed evolutionary history of the Milky Way so far.
About 13 billion years ago, the emergence of stars was violent and constant, but this rate of formation has decreased over time. “We might well have expected that the Milky Way did not form stars at a constant rate throughout its history, but we didn’t expect such well defined periods of great activity,” said Tomás Ruiz Lara, the study’s leader, in a statement.
As the astronomers explain, there were some moments in the history of the Milky Way when the rate of star formation increased surprisingly, reaching up to four times its normal value. One of these episodes occurred about 5 or 6 billion years ago, followed by others 2 billion years ago, 1 billion years ago, and 100 million years ago.
Why did these episodes of star formation happen? To understand the issue, we first need to know that the Milky Way, although it is in a relatively empty zone of the Universe, is not completely isolated. In our “neighborhood” are the Andromeda galaxy and dozens of much smaller galaxies, the “dwarfs”.
Among these galaxies, Sagittarius was and still is particularly important for the formation of the Milky Way. According to the new research, Sagittarius has approached our galaxy several times – and each time the rate of star formation has increased considerably.
“Everything indicates that these interactions between the two systems were able to stimulate the formation of new stars in our galaxy, drastically affecting its evolution,” said Carme Gallart, co-author of the research. “These results question some of the current models of star formation in galaxies, and put constraints on future theoretical studies.”
According to Tomás Ruiz Lara, the Solar System was formed about 4.7 billion years ago from the collapse of a large cloud of gas and dust. “It is possible that our Sun was one of the many stars formed some 5 billion years ago as a consequence of the interaction between our Galaxy and the Sagittarius galaxy,” noted the expert. “It could be that we are witnessing one of the key astronomical events which gave rise to the world as we know it today.”