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The Gaia telescope reveals the last secrets of the turbulent Milky Way

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It is a fantastic day for astronomy, opening the door to new discoveries about the Universe and our galaxy.said Josef Aschbacher, Director General of the European Space Agency (ESA) during the presentation of the results of Gaia, one of the flagship scientific missions of the agency launched in 2013.

The space observatory, which is stationed 1.5 million kilometers from Earth, in front of the Sun, is in its third data collection, intended to map our galaxy in all its dimensions, and therefore to understand its origin. the structure and dynamics.

Equipped with two telescopes and a billion-pixel photographic sensor, Gaia scans a very small part (just 1%) of the stars in our galaxy, whose diameter measures 100,000 light years.

The figures unveiled on Monday are incredible: By analyzing the 700 million data sent to Earth every day for 34 months, Gaia was able to provide information on over 1.8 billion stars.

An unprecedented set of details are provided, such as these 220 million photometric spectra, which will allow us to estimate the mass, color, temperature and age of stars for the first time. And 2.5 million new chemical compositions, this one DNA providing information on the birthplace of stars and their journey across the galaxy.

Or 35 million radial velocities, which measure the displacement of stars and offer a new understanding of the movements of the Milky Way.

Surprise for scientists: Gaia spotted her for the first time tremors stellar, tiny movements on the surface of a star that change its shape. Discovery opens a gold mine for the astroseismology of massive starsnamely their internal workings, explained Conny Aerts, from the University of Leuven, Belgium, member of the Gaia collaboration.

At all levels, Gaia exceeds expectationswelcomed François Mignard, scientific director of the Gaia mission for France, to the Agence France-Presse (AFP).

The findings, which gave rise to some fifty scientific articles in the process, paint the portrait of a galaxy much more turbulent than expected, the astronomer of the Côte d’Azur Observatory told AFP.

It was thought to have reached a steady state, swirling gently, like a fluid mixed gently with a wooden spoon. But not at all! explains François Mignard.

His eventful life is instead made up of accidents, unexpected movements and not as simple as this spiral he describes. For example, our solar system “does not simply rotate in a perpendicular plane; rises and falls, above and belowsays François Mignard.

It is also home to a very heterogeneous population of stars, some of which weren’t present from the start, but may have been swallowed along the way through interactions with the nearby dwarf galaxy of Sagittarius.

Our galaxy is a beautiful melting pot of starssums up Alejandra Recio-Blanco, from the Côte d’Azur Observatory.

Gaia’s level of accuracy is such it will allow us to retrace the Milky Way’s past in over 10 billion yearsadded Anthony Brown, president of the international consortium DPAC, the ground processing chain for the data stream sent by Gaia.

Stars have the particularity of living for billions of years: analyzing them is equivalent to studying a fossil, informing us about the state of the galaxy during its formation, astronomers point out.

With the second catalog, delivered in 2018, astronomers were able to prove that our galaxy had purr with another 10 billion years ago.

The new catalog also offers unmatched precision measurements for 156,000 asteroids in our solar system, analyzing the composition of 60,000 of them.

It will take five years to deliver this third catalog of observations distributed from 2014 to 2017. And we will have to wait until 2030 to get the final version, when Gaia has finished scanning space, in 2025.

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