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Madrid, November 2 (EUROPA PRESS). – 10,000 million years ago, the Milky Way merged with the great galaxy Gaia-Enceladus. Its stars constitute the essential halo halo and form its thick disc, giving it its inflated appearance.
Description of this mega fusion, discovered by an international team led by the astronomer of the University of Groningen, the Netherlands, Amina Helmi, is now published in the scientific journal Nature & ' # 39 ;.
Large galaxies such as the Milky Way result from the fusion of smaller galaxies. An important question is whether a galaxy such as the Milky Way is the product of many small or large fusions.
University of Groningen astronomy professor Amina Helmi has spent most of her career looking for "fossils" in our Milky Way, which could provide clues to her evolution. He uses the chemical composition, the position and the trajectory of the stars in the halo to deduce the history and thus identify the fusions that created the original Milky Way.
Second recent publication of Gaia satellite mission data. Last April, he provided Professor Helmi with data on approximately 1,700 million stars. Helmi has been involved in the development of the Gaia mission for about 20 years and was part of the data validation team at the second data release.
This scientist is now using the data to look for melting marks in the halo. . "We were hoping to find molten satellite stars in the halo, which we did not expect to find is that most halo stars actually have a common origin in a great fusion," says the expert.
In particular, she found that the chemical signature of many halo stars was clearly different from the "native" stars of the Milky Way. "And they form a fairly homogeneous group, which indicates that they share a common origin," he said, noting that, during the course of the trajectory and the chemical signature, the "invaders" clearly distinguished.
Helmi explains: "The youngest stars of Gaia-Enceladus are actually younger than the stars of the Milky Way native to what is now the region of the thick disc.This means that the offspring of this thick disc was already present when the merger took place and Gaia-Enceladus, because of its large size, shook and inflated it. "
In a previous article, Helmi had already described a large" bubble " "Stars that share a common origin. Now, this shows that the stars of this halo spot are the debris of the Milky Way fusion with a galaxy a little more mbadive than the Little Magellanic Cloud, about 10,000 million years ago. The galaxy is called Gaia-Enceladus, in honor of the giant Enceladus who, in Greek mythology, was born of Gaia (the goddess of the Earth) and Uranus (the god of heaven) .
Data on kinematics, chemistry, age and distribution The stars of the Milky Way and the remains of Gaia-Enceladus reminded Helmi of the simulations performed by a former doctoral student a dozen years ago. 39; years. His simulations of the fusion of a large disk-shaped galaxy with the young Milky Way produced a star distribution of the two objects, which is completely consistent with Gaia's data. "It was amazing to see the new Gaia data and realize that I had seen them before," he says.
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