Astronomers are dizzy: The Gaia space telescope on Monday delivered its new data on nearly two billion stars in the Milky Way, with incredible precision that makes it possible to create a map of our galaxy bursting with life.
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“It’s a fantastic day for astronomy, opening 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 Gaia results, one of the scientific flagships of the Agency missions launched in 2013.
The space observatory, stationed 1.5 million kilometers from Earth across from the Sun, is in its third data harvest, designed to map our galaxy in all its dimensions, thus understanding its origin, structure and dynamics.
Equipped with two telescopes and a billion-pixel photo sensor, Gaia is scanning a very small fraction (just under 1%) of the stars in our galaxy, which are 100,000 light-years across.
The numbers revealed on Monday are unimaginable: By analyzing the 700 million data sent to Earth every day for 34 months, Gaia was able to provide information about more than 1.8 billion stars.
A wealth of unprecedented detail is provided, such as these 220 million photometric spectra, making it possible for the first time to estimate the mass, colour, temperature and age of stars. And 2.5 million new chemical compounds, that “DNA” that informs about the birthplace of the stars and their journey through the galaxy.
Or 35 million radial velocities measuring the displacement of stars and offering a new understanding of the Milky Way’s movements.
Surprise for scientists: Gaia has detected for the first time stellar “tremors”, tiny movements on a star’s surface that change its shape. The discovery opens “a gold mine for ‘asteroseismology’ of massive stars,” namely their inner workings, explained Conny Aerts of the University of Louvain, Belgium, a member of the Gaia collaboration.
“On all levels, Gaia is exceeding expectations,” welcomes AFP François Mignard, scientific director of the Gaia mission to France.
The results, which led to around fifty scientific articles, paint a portrait of a galaxy that was “much more turbulent” than expected, the Coastal Observatory astronomer told AFP: “We thought it had reached a steady state that was gently moving.” rotates by itself, like a liquid gently stirred with a wooden spoon. But not at all!” develops François Mignard.
On the contrary, her “‘life as a Patachon’ is made up of accidents, unexpected movements and is not as simple” as this spiral she describes. For example, “Our solar system is not content to rotate in a vertical plane, it goes up and down, up and down”, specifies François Mignard.
It’s also home to a very heterogeneous population of stars, some of which weren’t there to begin with but may have been “swallowed” along the way by interactions with the nearby Sagittarius dwarf galaxy.
“Our galaxy is a magnificent melting pot of stars,” summarizes Alejandra Recio-Blanco of the Côte d’Azur Observatory.
Gaia’s level of precision is so high that it “will allow us to track the Milky Way’s past for 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 peculiarity of living for billions of years: analyzing them is equivalent to examining a fossil, which tells us about the state of the galaxy during its formation, astronomers point out.
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 measurements of unprecedented precision for 156,000 asteroids in our solar system and breaks down the composition of 60,000 of them.
It will have taken five years to deliver this third catalog of observations from 2014 to 2017. And it will be necessary to wait until 2030 to get the final version, when Gaia will have finished scanning space in 2025.