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Using data from the European Gaia satellite, researchers have discovered many unusual substructures in the Milky Way galaxy. The analysis suggests that these substructures were probably caused by a near-collision between the Milky Way and a dwarf galaxy, Sagittarius. The structures remained hidden until Gaia brought them to light.
"We observed different shapes of morphologies, such as a spiral similar to that of a snail shell. The existence of these substructures was observed for the first time thanks to the unprecedented accuracy of the data provided by the Gaia satellite, from the European Space Agency (ESA), said Teresa Antoja, in charge of at the Gaia mission. "These substructures allow us to conclude that the disk of our galaxy has undergone significant gravitational disturbance about 300 and 900 million years ago."
When the small galaxy passed near the Milky Way, it disrupted the gravitation of millions of stars. The phenomena influenced the movement of nearly six million stars in the disk of our galaxy and let them move like ripples on a pond.
"It's a bit like throwing a stone into a pond, which moves water in the form of waves and waves," Antoja said.
"One of the most remarkable forms we have seen is the spiral pattern of stars near the sun, which had never been seen before. In fact, the shapes observed in the graphs were so clear (as opposed to the usual cases) that we thought this might be an error in the data. "
The researchers performed many tests on the data to look for errors, but the results remained consistent and never changed. Accepting this only leads to a logical conclusion: the substructures do indeed exist in the Milky Way. The presence of these features also implies that the disk of our galaxy is dynamically young and continues to change over time.
"We know that our galaxy is" cannibal "and grew up eating other small galaxies, as it does with the Sagittarius dwarf galaxy," said Amina Helmi, researcher at the University of Groningen.
The discovery was made possible thanks to the Gaia satellite of the European Space Agency. Launched in 2013, Gaia not only accurately measures the positions of stars, but also provides accurate information on their movements in the plane of the sky.
"It's exactly the kind of discovery we were hoping to get from Gaia's data," said Timo Prusti, Gaia project scientist at ESA. "The Milky Way has a rich story to tell and we start reading this story."
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