Gaia presents a map of the Milky Way without equal

published Saturday, June 11, 2022 at. 16:23.

The Gaia mission, whose space telescope draws a detailed map of the Milky Way, on Monday reveals a new version rich in information about nearly two billion stars, the course of which it follows and analyzes its properties.

“It is the Swiss Army knife of astrophysics. There is not a single astronomer who will not use its data, directly or indirectly,” the astronomer from the Côte d’Observatoire told AFP. ‘Azur, François Mignard, responsible for Gaia for France.

The community of astronomers will be able to draw from Monday from 6 p.m. 10:00 GMT in the third catalog of data collected by the instrument. A harvest, accompanied by about fifty scientific articles, which list a wealth of celestial bodies.

From the nearest, with more than 150,000 asteroids in our solar system, “whose orbital instrument has calculated with incomparable precision,” says Mr. Mignard, for new measurements concerning more than 1.8 billion stars in the Milky Way. And beyond this galaxy: populations of other galaxies and distant quasars.

Launched on behalf of the European Space Agency (ESA), the Gaia Telescope has been in operation since 2013, stationed at a privileged position called the L2, one and a half million kilometers from Earth, opposite the Sun.

– Scan the sky –

“Gaia scans the sky and captures everything it sees,” sums up astronomer Misha Haywood at the Paris PSL Observatory. It detects and observes a very small proportion (almost 1%) of the stars in our galaxy, whose diameter measures 100,000 light-years.

But he establishes much more than a simple card. Its two telescopes are connected by a photographic sensor of one billion pixels, where a commercial camera counts in millions. Three astrometry instruments, photometry and spectroscopy, will interpret the photons, real light signals, thus being restored.

“Thanks to this, it provides a global observation of the positions of what is moving in the sky. This is the first time,” continues Mr. Haywood. Before Gaia, “we had a really limited view of the galaxy”.

Before Gaia? It was Hipparcos, the satellite that revolutionized observation after its launch by ESA in 1997, and cataloged more than 110,000 celestial bodies.

With Gaia, astronomers not only have access to positions and movements of a large number of stars, but also to measurements of their physical and chemical grades and, just as importantly, their age.

So much information “that informs us about their previous evolution and therefore about the galaxy”, explains astronomer Paola di Matteo, colleague of Misha Haywood at the Paris-PSL Observatory.

– Great discoveries –

This is also “one of the reasons Gaia was built”, the astronomer continues. “Stars have the peculiarity of living for billions of years. Their target is therefore like a fossil that tells us about the state of the galaxy at the time of their formation.”

This overview of the movements of the stars in the Milky Way has already led to great discoveries. With the second catalog, delivered in 2018, astronomers were able to show that our galaxy was “fused” another ten billion years ago.

The catalog has given rise to thousands of scientific articles since its first edition in 2016. The data flow requires a dedicated soil treatment chain, DPAC, which calls for supercomputers from six European computer centers, and the mobilization of 450 specialists, explains François Mignard, who was in charge.

“Without this treatment group, there is no mission” because Gaia produces 700 million star positions, 150 million photometry measurements and 14 million spectra every day. A stream of raw data that “man-made” algorithms transform into measurements that can be used by astronomers.

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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