Gaia reveals the last secrets of the turbulent Milky Way

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Paris (AFP) – Astronomers are dizzying: The Gaia Space Telescope delivered its new data of nearly two billion stars in the Milky Way on Monday, with incredible precision that makes it possible to draw a map of our galaxy bubbling with life.

“It’s an amazing day for astronomy, which opens the floodgates for new discoveries about the universe and our galaxy,” said Josef Aschbacher, Director General of the European Space Agency (ESA), during the presentation of Gaia results, one of the agency’s flagship science missions launched in 2013.

The space observatory, located 1.5 million kilometers from Earth to the Sun, is in its third data harvest, intended to map our galaxy in all its dimensions and thus understand its origin, its structure and its dynamics.

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

The numbers revealed on Monday are incalculable: By analyzing the 700 million data sent to Earth every day, for 34 months, Gaia was able to provide information on more than 1.8 billion stars.

– “Patachons liv” –

A host of unprecedented details are provided, such as these 220 million photometric spectra, which will allow for the first time to estimate the mass, color, temperature and age of stars. And 2.5 million new chemical compounds, this “DNA” informs about the birthplace of the stars and their journey through the galaxy.

“You are here”: an artist’s impression of the Milky Way made possible thanks to Gaia EUROPEAN SPACE AGENCY / AFP

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

Surprise for scientists: Gaia first discovered the star “quake”, small movements on the surface of a star that changed its shape. The discovery opens “a goldmine for + the asteroseismology + of massive stars”, namely their inner function, explained Conny Aerts from the University of Louvain (Belgium), who is a member of the Gaia collaboration.

“At all levels, Gaia exceeds expectations,” welcomes AFP François Mignard, Scientific Head of the Gaia Mission for France.

A map of the galaxy made from Gaia data, provided June 13, 2022 by ESA
A map of the galaxy made from Gaia data, provided June 13, 2022 by ESA EUROPEAN SPACE AGENCY / AFP

The results, which gave rise to about fifty scientific articles in the process, paint the portrait of a galaxy “much more turbulent” than expected, told AFP, the astronomer from the Observatory of the Coast. Azure

“We thought it had reached a stationary state, turning it gently around itself, like a liquid gently stirred with a wooden spoon. But not at all!”, François Mignard develops.

Her “+ life as a patachon + consists on the contrary of accidents, unexpected movements and not as simple” as this spiral she describes. For example, our solar system is “not content to rotate in a perpendicular plane, it goes up and down, above and below,” specifies François Mignard.

“The melting pot of the stars”

It is also home to a very heterogeneous population of stars, some of which were not there from the start, but which may have been “swallowed up” along the way through interactions with the nearby Sagittarius’ dwarf galaxy.

“Our galaxy is a magnificent melting pot of stars,” sums up Alejandra Recio-Blanco of the Côte d’Azur Observatory.

Reconstruction of the orbit of more than 150,000 asteroids, image provided by ESA on June 13, 2022
Reconstruction of the orbit of more than 150,000 asteroids, image provided by ESA on June 13, 2022 EUROPEAN SPACE AGENCY / AFP

Gaia’s level of precision is such that it “will allow us to trace the Milky Way’s past over more than 10 billion years,” added Anthony Brown, president of the international consortium DPAC, the soil treatment chain for the data stream sent by Gaia.

Stars have the special thing about living for billions of years: analyzing them is like studying a fossil, informing us about the state of the galaxy during its formation, astronomers emphasize.

With the second catalog, delivered in 2018, astronomers were able to show that our galaxy was “fused together” 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 have taken five years to deliver this third catalog of observations spread from 2014 to 2017. And it will be necessary to wait until 2030 to get the final version, when Gaia finishes scanning the space, in 2025.

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