Paris (AFP)
The Milky Way absorbed the galaxy Gaia-Enceladus during their collision ten billion years ago, a shock that would have generated new stars for 4 billion years according to a study published Monday.
Astronomers have long sought to understand whether the Milky Way has fed on several collisions with "small" galaxies or has grown with only one large impact.
To unravel the various existing theories on the subject, astronomers have plunged into the data collected by the European Space Telescope Gaia, co-produced by Airbus and put into orbit by the European Space Agency in 2013.
The satellite mapped nearly 1.7 billion stars in our galaxy, determining for some of them position, distance to Earth and brightness.
These data had already allowed astronomers to establish in 2018 that the galactic halo surrounding the Milky Way consisted mainly of debris from its collision with the Gaia-Enceladus galaxy about 3.8 billion years after the Big Bang.
"The novelty of our work is that we have been able to assign precise ages to stars coming from both galaxies," Carme Gallart, co-author of the study published in Nature Astronomy, told AFP.
Highlighting that the collision would have generated "violent outbreaks of star formation" for 4 billion years.
"It's a very gradual process - nothing to do with a car accident - it's something that affects the galaxy as a whole, it's very massive, so it's slowly happening on a human scale, not so slowly on the cosmic scale, "explains Carme Gallart.
© 2019 AFP