An international team of researchers, using complex computer models powered by artificial intelligence, has created the family tree of the Milky Way. Scientists said that the galaxy underwent the largest collision in history 11 billion years ago, when it was in the formation stage.
The study was published in the Monthly Notices of the Royal Astronomical Society, the Daily Mail reports.
Scientists previously knew that galaxies can grow by merging smaller galaxies, but until now, the origin of our own galaxy has been a mystery. To determine how our ancient galaxy grew to its enormous size, scientists analyzed globular clusters – dense groups of up to a million stars that can act as building blocks for huge galaxies.
The Milky Way contains more than 150 such clusters, many of which formed in smaller galaxies that coalesced to form the galaxy we live in today.
According to scientists, throughout its history, the Milky Way has cannibalized about five galaxies with over 100 million stars and about 15 with at least 10 million stars. The largest ancestor galaxies collided with the Milky Way between 6 and 11 billion years ago, the researchers say.
An international team of researchers led by Dr. Diederik Kruissen of the University of Heidelberg Astronomy Center (ZAH) and Dr. Joel Pfeffer of the University of Liverpool John Moors have developed a computer simulation of the Milky Way called E-Mosaics that has helped unravel its mystery.
In simulations, researchers have been able to link the age, chemical composition, and orbital movements of globular clusters to primitive galaxies that created them more than 10 billion years ago.
By applying this insight to a group of globular clusters in the Milky Way, they could determine how many stars these ancestor galaxies contain.
It also allowed researchers to get an idea of when they merged into the Milky Way. By mapping them all, the researchers created the complex image of galaxy interactions that we see today.
Intergalactic collisions were common in the past of our galaxy, but the influence of the mysterious Kraken, named for the legendary mythical sea monster of gigantic proportions, was so great that it changed the face of our home galaxy.
Other notable collisions and mergers are the Helmi Streams event, which occurred about 10 billion years ago, and a smaller event called Sequoias about a billion years later. 9 billion years ago, according to scientists, the Milky Way collided with the Gaia-Enceladus galaxy, but the merger with the Kraken happened 11 billion years ago, when the Milky Way was four times less massive.
“The collision with the Kraken was perhaps the most significant merger that ever happened on the Milky Way. It really changed the appearance of the Milky Way at the time, ” Dr. Diederik Kruissen said, co-author of the study at the University of Heidelberg.