Researchers decipher the Milky Way’s family tree

Astrophysicists used complex computer models powered by artificial intelligence to produce an ancestral family tree of the Milky Way.

The research revealed that the Milky Way, when it was in its formation stages some 11 billion years ago, suffered its largest collision ever.

Intergalactic collisions were common in our galaxy’s past, but the impact of the enigmatic Kraken was so great that it changed the very appearance of our galaxy.

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Other noteworthy collisions and mergers are the ‘Helmi Streams’ event about 10 billion years ago and the smaller Sequoia event about a billion years later.

Shortly after Sequoia came Gaia-Enceladus, nine billion years ago, which was previously thought to be the largest collision ever seen from the Milky Way, before astronomers discovered the Kraken.

Dr Diederik Kruijssen, co-author of the study from the University of Heidelberg, said: ‘The collision with Kraken must have been the most significant merger ever experienced by the Milky Way.

“Previously, a collision with the Gaia-Enceladus-Sausage galaxy, which occurred about nine billion years ago, was thought to be the largest collision event.

However, the merger with Kraken happened 11 billion years ago, when the Milky Way was four times less massive.

“Consequently, the collision with Kraken must have really transformed the appearance of the Milky Way at that time.”

Scientists have long known that galaxies can grow from the merger of smaller galaxies, but until now the ancestry of our galaxy has been a mystery.

To determine how our ancient galaxy grew to its enormous size of over 100,000 light-years in diameter with spiral arms and a peanut-shaped core, the researchers turned to AI.

A neural network has been trained by academics to analyze globular clusters, dense clusters of up to a million stars.

These can serve as building blocks for vast galaxies and can be traced back to the dawn of the Universe, some 14 billion years ago.

The Milky Way is home to more than 150 of these clusters, many of which formed in the smaller galaxies that merged to form the galaxy we live in today.

Throughout its history, the Milky Way has cannibalized around five galaxies with more than 100 million stars and around 15 with at least 10 million stars.

The most massive progenitor galaxies collided with the Milky Way between six and 11 billion years ago, the researchers say.

For decades, astronomers have suspected that ancient clusters could be used as fossils to reveal the chronology of events in the Milky Way.

An international team of researchers led by Dr Diederik Kruijssen, at the Center for Astronomy at the University of Heidelberg (ZAH), and Dr Joel Pfeffer, at Liverpool John Moores University has developed a computer simulation of the Milky Way, called E -Mosaics, to help solve the mystery.

In the simulations, the researchers were able to relate the ages, chemical compositions and orbital motions of globular clusters to the primitive galaxies that created them more than 10 billion years ago.

By applying these insights to groups of globular clusters found in the Milky Way, it was possible to determine how many stars these progenitor galaxies contained.

It also allowed researchers to get information on when they merged into the Milky Way. By mapping them all, the researchers constructed a complex picture of the galaxy’s interactions, leading to the Milky Way we see today.

The research is published in Monthly Notice of the Royal Astronomical Society.