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Scientists know that galaxies can be formed by merging smaller ones. But the origin of our Milky Way remains a mystery today.
And recently, an international team of astrophysicists succeeded in reconstructing the first complete family tree of our galaxy, the Milky Way, by analyzing the properties of globular star groups, which revolve around them thanks to artificial intelligence. Notes from the Royal Astronomical Society ”(Monthly Notices from the Royal Astronomical Society).
Globular clusters
Globular clusters are dense clusters of stars with numbers of up to one million stars, and they’re roughly the same age as the universe, and the Milky Way galaxy is home to over 150 of these. clusters, many of which formed inside small galaxies that merged with each other earlier, to form the galaxy we live in today.
Astronomers have speculated for decades that globular clusters could be used as “fossils” to reconstruct the history of early galaxy assembly.However, this was only possible after developing the latest cosmic models based on precise observation results, carried out over the past few years.
In the new study, an international team of researchers led by Dr Diederik Croissen from the Center for Astronomy at ZAH University in Heidelberg and Dr Joel Fever from John Moores University in Liverpool were able to deduce the dates of the merger of the Milky Way. With other galaxies, and the reconstruction of its family tree using only globular star clusters, according to a statement from the University of Heidelberg.
Our galaxy’s family tree includes ancient galaxies, including the recently discovered “Kraken” (University of Heidelberg)Computer simulation
To achieve this, the researchers developed a series of advanced computer simulations to form galaxies similar to the Milky Way. Their simulations, called “electronic mosaic” (E-MOSAICS), are unique in that they include a comprehensive model for the formation, evolution and subversion of globular clusters.
In this process, the researchers were able to relate the ages of globular clusters, their chemical compositions and orbital motions to the characteristics of the ancient galaxies, in which they formed, more than 10 billion years ago.
By applying this simulation to groups of globular clusters in the Milky Way, they were able to determine how many stars these scattered galaxies contained when they merged into the Milky Way.
“The main challenge in relating the properties of globular clusters to the fusion history of the host galaxy has always been,” says Croissen. “The galaxy cluster is a very complicated process, in which the orbits of the globular clusters are completely reorganized.”
To understand the galactic system we see today, the study authors used artificial intelligence and created an artificial neural network on the simulation of “E-MOSAICS” to relate the properties of spherical mass to the date of the fusion of the host galaxies. After testing the algorithm tens of thousands of times, they were amazed at how accurately it is able to reproduce. Construction dates for the fusion of galaxies.
The discovery of an unknown ancestor of our galaxy
Based on their findings, the research team set out to decipher the history of the mergers that took place in the Milky Way, using groups of globular clusters, which are said to have formed in the same ancient galaxy based of its orbital motion.
By applying the neural network to these groups of globular clusters, the researchers were able not only to predict the stellar masses and fusion times of ancestral galaxies with great precision. Rather, they also revealed a hitherto unknown collision that occurred between the Milky Way and a mysterious galaxy, which they called “Kraken”, which occurred 11 billion years ago when the size of our galaxy did not exceed a quarter of its current size.
Scientists had believed that our galaxy’s biggest collision was the one that occurred about 9 billion years ago with the galaxy “Gaia Enceladus Sausage”, and the researchers say that these results in full. rebuild the first complete fusion tree for our galaxy.
Collision of galaxies (IC 2163) and (NGC 2207) This is how our galaxy was formed for billions of years (European Space Agency)Throughout its history, the Milky Way has devoured 5 galaxies that contain more than 100 million stars and around 15 galaxies with at least 10 million stars, and the largest ancient galaxies have collided with the Milky Way. on more than one occasion between 6 and 11 billion years ago.
The study authors expect their predictions to stimulate future studies to search for the remains of these scattered galaxies, and the researchers have already found remains of 5 of these galaxies, and with current and future telescopes, it is possible to find them all, they say.
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