La Voie lactée s’est formée au fil de nombreuses collisions avec d’autres galaxies plus petites. Une équipe internationale ajoute aujourd’hui une sixième de ces collisions à la liste déjà connue. Elle se serait produite il y a entre 8 et 10 milliards d’années. Ici, une image d'illustration. © ordus, Adobe Stock

Gaia finds the remains of galaxies that collided with the Milky Way

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the Milky Way It was formed about 12 billion years ago. Since then, like other galaxies that fillbeingI grew up in Collective And in size thanks to the numerous collisions. Over time, it has attracted smaller galaxies or clustersstars Which I literally absorbed. These foreign stars merge into his ranks. To understand how galaxies form, Astronomy scientists Need to learn more about these collisions.

They are searching tirelessly for the traces left in the Milky Way with these events fusion. In the data I return Mission Gaia, for example. Because it aims to accurately measure the location, distance and movement of stars in the Milky Way. This is how a international team I managed to draw a little more vividTree Genealogy of our galaxy.

Everything is played in Milky way aura. A region that extends far beyond the main part of our galaxy. This is where we find what astronomers call stellar streams. They are formed from stars in small galaxies that collide relatively slowly with the Milky Way. When the collision is more brutal, the stars – but also ball groups In particular – small galaxies find themselves randomly scattered in our halo.

Five collisions…plus at least one

This time, astronomers studied about 170 globular clusters, 41 stellar streams, and 46 satellite galaxies of the Milky Way. By analyzing their trajectories and all the kinetic data available to them using ultra-powerful algorithms, they showed that 25% of them fall into six large groups. Six large groups, each corresponding to a previous collision.

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Most of the galaxy mergers identified were already known to researchers. But this work makes it possible to identify the parent galaxies of different globular clusters, stellar streams or satellite galaxies. Hence, a shortage of currents metal C-19, Sylgr, Phoenix It will come from a merger with the LMS-1/Wukong galaxy. What do we consider a galaxy to have formed so early After the Big Bang.

This collision with LMS-1/Wukong, which astronomers already knew about, just like the galaxies of Cetus, Gaia-Sausage/Enceladus or Arjuna/Sequoia/Iitoi, all occurred about eight to ten billion years ago. Years. The collision with Sagittarius – already identified in the past – looks more recent. It can be dated from 5 to 6 billion years ago ” Just “. Because it is very “active”.

A sixth, hitherto unknown, collision appeared in eyes researchers. They named it Pontus – which means “married” – As one of the first sons Jaya Greek goddess of the land. This event must have also occurred about 8-10 billion years ago. And there are already rumors of a seventh merger that could be hiding in the data…

Galaxy: Genealogy of the Milky Way reveals a big surprise

Use the globular clusters hosted by the Milky Way as markers of its history and evolution. Astronomers dream about it. They’ve now finally managed to put the puzzle pieces back together to reveal our galaxy’s family tree. Thanks a lot for the contributionartificial intelligence.

Article from Natalie Mayer Posted on November 16, 2020

In the vastness of the universe, the Intergalactic collisionViolent as it is, it is not uncommon. Even these collisions are believed to have shaped the faces of the galaxies we observe today. for the first time, Researchers at the University of Heidelberg (Germany), among others, has succeeded in reconstructing the history of collisions suffered by the Milky Way.

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To establish our galaxy’s family tree, astronomers have relied on two tools: globular clusters and artificial intelligence. the Milky WayIn fact, it hosts more than 150 known globular clusters, dense assemblies of hundreds of thousands of stars about the same age as the universe. Most of it formed into small galaxies that eventually merged to form our galaxy. However, it is the latest observations and more complex models that have made it possible to trace the thread of history.

The researchers launched simulations – called E-MOSAICS – to link the globular clusters hosted by the Milky Way to the galaxies that saw them born. How do we rebuild our galaxy family tree. Here, a simulation of galaxy formation similar to the Milky Way is shown. Globular clusters are indicated by colored dots that symbolize their formation. Over time, the merger of the central galaxy with smaller satellite galaxies results in a large number of globular clusters. The ages, chemical composition, and orbits of these clusters reveal the mass of the parent galaxy in which they formed, but also when that galaxy merged with the central galaxy. © J. Pfeffer, D. Kruijssen, R. Crain, N. Bastian, University of Heidelberg

The simulations conducted by the researchers – which they call E-Mosaics – include a comprehensive model of formation, evolution and destruction ball groups. It is enough to relate the ages, chemical compositions, and orbital motions of these clusters to the properties of the galaxies in which they were born more than 10 billion years ago. And determine not only the number of stars from which these galaxies formed, but also when they collided with the Milky Way.

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Amazingly accurate simulation

It is to tame the complex process that astronomers have used artificial intelligence. “We formed artificial nerve network on our simulations. We’ve tested the algorithm tens of thousands of times, and have been amazed at how accurately it reconstructs the dates of simulated galaxy mergers from the constellations of its globular clusters alone. “Comments by researcher Diederick Kruijssen at A Press release from the University of Heidelberg.

This method was applied to the Milky Way, and it sheds light on the history of the mergers that formed our galaxy. Thus the Milky Way has swept approximately five galaxies with more than 100 million stars and about fifteen of at least 10 million stars. The largest collisions occurred between 6 and 11 billion years ago. Like the collision with the Gaia-Enceladus galaxy that occurred about 9 billion years ago.

11 billion years ago, it was the most important collision.

The method even revealed a previously unknown collision between the Milky Way and a galaxy called Kraken. “The biggest collision our galaxy has ever seen.” It would have happened 11 billion years ago. The Milky Way was then four times less massive.

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