Astronomers are stunned: on Monday, the Gaia Space Telescope delivered its new data on nearly two billion stars in the Milky Way, with incredible accuracy that allows it to map our galaxy, seething with life.
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“It is a fantastic day for astronomy, which opens the door to new discoveries about the Universe and our galaxy”, exulted Josef Aschbacher, director general of the European Space Agency (ESA) during the presentation of the results of Gaia, one of the flagships of the scientific agency missions launched in 2013.
The space observatory, which is stationed 1.5 million kilometers from the Earth in front of the Sun, is in its third data collection, destined 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 data unveiled on Monday is beyond comprehension: 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 “DNA” that informs about 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 has identified for the first time stellar “tremors”, small movements on the surface of a star that change its shape. The discovery opens “a gold mine for the ‘asteroseismology’ of massive stars”, particularly their internal workings, explained Conny Aerts of the University of Louvain (Belgium), a member of the Gaia collaboration.
“At all levels, Gaia exceeds expectations”, welcomes the AFP François Mignard, scientific director of the Gaia mission for France.
The results, which gave birth to about fifty scientific articles in the process, paint a picture of a galaxy “much more turbulent” than expected, the astronomer at the Observatory of the Coast told AFP. Azur “We thought it had reached a steady state, turning gently by itself, like a fluid mixed gently with a wooden spoon. But not at all!”, Explains François Mignard.
His “patachon life” is instead made up of accidents, unexpected and not so simple movements “like this spiral he describes. For example, our solar system “is not content with rotating in a perpendicular plane, it goes up and down, up and down”, explains François Mignard.
It is also home to a very heterogeneous population of stars, some of which were not 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 magnificent melting pot of stars”, sums up Alejandra Recio-Blanco of the Côte d’Azur Observatory.
Gaia’s level of accuracy is such that “it allows us to retrace the Milky Way’s past in over 10 billion years,” added Anthony Brown, president of the international consortium DPAC, the ground-based processing chain of 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 demonstrate that our galaxy had “merged” with another ten billion years ago.
The new catalog also offers unmatched precision measurements for 156,000 asteroids in our solar system, breaking down 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 the space, in 2025.