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<a rel = "lightbox" href = "https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/2018/gaiadetectsa.jpg" title = "The spiral shape of fig 1c of Nature The article appears inside an old watch symbolizing the fact that these data allowed us to trace back to the disruption that shook the disk of the Milky Way. This figure shows how, from the new Gaia data obtained, we can learn more about the past of the galaxy. Credit: Crèdit: Edmon de Haro / iStock ">
The spiral shape of fig 1c of Nature The article appears inside an old watch symbolizing the fact that these data allowed us to trace back to the disruption that shook the disk of the Milky Way. This figure shows how, from the new Gaia data obtained, we can learn more about the past of the galaxy. Credit: Crèdit: Edmon de Haro / iStock
A team led by researchers from the Institute of Cosmic Sciences of the University of Barcelona (ICCUB, UB-IEEC) and the University of Groningen discovered, thanks to Gaia's data analysis, sub- previously unknown Milky Way structures. The results, arising from the combination of positions and the speed of 6 million stars of the galactic disk, were published in the journal. Nature.
"We observed different shapes of morphology, like a spiral similar to that of a snail.The existence of these substructures was observed for the first time thanks to the unprecedented precision provided by the Gaia satellite of the European Space Agency (ESA), "says Teresa Antoja, a researcher at ICCUB (IEEC-UB) and the first signatory of the article." These substructures allow us to conclude that the disk of our galaxy has undergone a gravitational disturbance. important about 300 and 900 million years ago. "This is one of the first discoveries of" galactic archeology "following the release of Gaia data; These data could allow researchers to discover the origins and evolution of the Milky Way.
What caused this disruption? To answer this question, the researchers compared the structure and the level of torsion of the spiral with models of the dynamics of the galaxy. They developed a hypothesis that the disturbance was caused by the dwarf galaxy Sagittarius passing near the disk of the Milky Way.
"The study undoubtedly implies that the disc of our galaxy is dynamically young, sensitive to disturbances and changing over time," says Antoja. "One of the most remarkable forms we've seen is the spiral pattern of stars near the sun, which had never been seen before.In fact, the shapes seen in the graphics were so clear (unlike the common cases ) error in the data, "says Antoja. More than 100 European engineers and scientists, among whom UB played a leading role, worked for months on Gaia data verification and validation tasks. As part of this task, Mercè Romero Gómez, researcher at UB, said: "With the simulations performed at UB, we could also reproduce the observed spirals".
Similar to a stone falling into a pond and creating waves that propagate to the surface, or a magnet approaching fillings pushed back in a particular direction, the stars of the galactic disk have been reordered in some way after the gravitational attraction from the satellite galaxy that has passed by them. After a while, the stars maintained the effects of the disturbance that shook them in their movements, and now a spiral can be seen in the graphs.
Amina Helmi, a researcher at the University of Groningen, says: "We know that our galaxy is" cannibal "and grew up eating other small galaxies, as it does with the Sagittarius dwarf galaxy. Nevertheless, the expert notes that "the mass of Sagittarius is still sufficient to cause a significant gravitational impact". What researchers are now observing does not respond to a collision between galaxies, but rather to Sagittarius, which is close to the galactic disk of the Milky Way.
First results of the new version of Gaia
The data analyzed in this study is part of the second version of Gaia, published on April 25, 2018. "UB scientists and engineers played a vital role in producing these data," explains Xavier Luri, director of ICCUB and coordinator of the team that built the Gaia archive. The effort of more than 400 scientists and engineers has allowed to publish precise positions and movements for more than 1,300 million objects. This second catalog, which gathers the first 22 months of data collection, has released the first spectroscopic data of a few million stars in the solar environment, allowing researchers to measure the speed of stars in our line of sight and get the three velocity coordinates of the stars. These data allowed the discovery which has now been published in Nature.
Now the Gaia satellite has logged more than 48 months of successful operations and ESA has extended the mission until the end of 2020. ESA is currently evaluating a second two-year mission. UB researcher Carme Jordi, a member of Gaia's science team, says: "All indications are that this is just one of the first discoveries of a series of new discoveries and hidden surprises in the world. Gaia data released in April – the tip of the iceberg. study of the origins and evolution of the galaxy in which we are. "
Explore more:
New GAIA data reveals fusions in the Milky Way
More information:
T. Antoja et al, a dynamically young and disrupted Milky Way disk, Nature (2018). DOI: 10.1038 / s41586-018-0510-7
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