The Gaia space telescope delivered its new data on nearly two billion stars in the Milky Way on Monday, with unprecedented precision that makes it possible to draw up a map of our galaxy, bubbling with life.
“It’s a fantastic 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 the results of Gaia, one of the agency’s flagship scientific missions launched in 2013.
The space observatory, stationed 1.5 million kilometers from Earth opposite 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 photographic sensor of one billion pixels, Gaia scans a very small part (barely 1%) of the stars of our galaxy, whose diameter measures 100,000 light years.
The figures unveiled Monday are beyond comprehension: by analyzing the 700 million data sent to the ground every day, for 34 months, Gaia was able to provide information on more than 1.8 billion stars.
A host of unprecedented details are delivered, such as these 220 million photometric spectra, which will make it possible to estimate for the first time the mass, color, temperature and age of stars. And 2.5 million new chemical compositions, this “DNA” informing about the birthplace of stars, and their journey through 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 for the first time stellar “tremors”, tiny movements on the surface of a star which modify its shape. Discovery opens “a gold mine for +the asteroseismology+ of massive stars”, namely their inner workings, explained Conny Aerts of the University of Leuven (Belgium), a member of the Gaia collaboration.
“At all levels, Gaia exceeds expectations”, welcomes AFP François Mignard, scientific manager of the Gaia mission for France.
The results, which gave rise to around fifty scientific articles in the process, paint the portrait of a galaxy “much more turbulent” than expected, told AFP the astronomer of the Observatory of the Coast. Azure
“We thought she had reached a stationary state, gently turning on itself, like a fluid gently stirred with a wooden spoon. But not at all!”, develops François Mignard.
on “+patachon’s life+ is on the contrary made up of accidents, unexpected and not so simple movements” than this spiral that it describes. For example, our solar system “does not just turn in a perpendicular plane, it goes up and down, above and below”says François Mignard.
“Crucible of Stars”
It is also home to a very heterogeneous population of stars, some of which were not there from the outset but may have been “swallowed up” along the way through interactions with the nearby Sagittarius dwarf galaxy.
“Our galaxy is a magnificent crucible of stars”, summarizes Alejandra Recio-Blanco of the Côte d’Azur Observatory.
Gaia’s level of precision is such that it “will allow us to trace the past of the Milky Way over more than 10 billion years”, added Anthony Brown, president of the international consortium DPAC, the ground processing chain of the data stream sent by Gaia.
Stars have the particularity of living for billions of years: analyzing them is the equivalent of studying a fossil, informing us about the state of the galaxy during its formation, underline the astronomers.
With the second catalog, delivered in 2018, astronomers were able to show that our galaxy had “merged” with another ten billion years ago.
The new catalog also offers unrivaled 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 obtain the final version, when Gaia will have finished scanning space, in 2025.