Gaia offers a unique map of the Milky Way

It is the Swiss Army knife of astrophysics. There is not a single astronomer who does not use his data directly or indirectly, French Coast Observatory astronomer François Menard told AFP, responsible for Gaia in France.

The community of astronomers will be able to extract from Monday from the third catalog of data collected by the instrument, a harvest, accompanied by about fifty scientific articles, which lists a series of celestial bodies.

Functional telescope since 2013

From the nearest, with more than 150,000 asteroids in our solar system, whose orbital instrument was calculated with unparalleled accuracy, it is making new measurements of more than 1.8 billion stars in the Milky Way, says Maynard. And outside of this galaxy, groups of other galaxies and distant quasars.

Launched by the European Space Agency (ESA), Gaia has been in operation since 2013, and is located in a privileged place, called L2, a million and a half kilometers from Earth, facing the Sun.

Gaia is scanning the sky and capturing everything she sees. »

– Quote from Misha Haywood, astronomer at the PSL Observatory in Paris

It detects and observes a very small fraction (barely 1%) of the stars in our galaxy, which are 100,000 light-years away.

But it draws more than just a map. Its two telescopes are connected to a billion-pixel photo sensor, with millions of commercial cameras.

Three instruments of astronomy, photometric and spectroscopic will interpret, and later recover, photons and real light signals.

Thanks to this, it provides a global tracking of the positions of what moves in the sky. this is the first time. Before Gaia, we had a very limited view of the galaxy. »

– Quote from Misha Haywood, astronomer at the PSL Observatory in Paris

before Gaia? It was Hipparcos, the satellite that revolutionized observation after its launch by the European Space Agency in 1997 by cataloging more than 110,000 celestial bodies.

With Gaia, astronomers can access not only the positions and motions of a large number of stars, but also the measurements of their physical and chemical characteristics and, most importantly, their age.

A lot of information that tells us about its evolution in the past and therefore about the evolution of the galaxy explains the astronomer Paula Di Matteo, Misha Haywood Fellow of the Observatoire de Paris-PSL.

It is also one of the reasons for building Gaia, the astronomer continues.

“Stars have a peculiarity that billions of years ago. Thus, its measurement is similar to that of a fossil that tells us about the state of the galaxy at the time of its formation. »

– Quote from Paula Di Matteo, astronomer

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 integrated Ten billion years ago.

The catalog has generated thousands of scientific articles since its first launch in 2016. The data flow requires a specialized terrestrial processing chain, DPAC, which convenes supercomputers for six European computer centers, mobilizing 450 specialists, explains François Menard, who he was responsible for it.

Without this healing kit, there would be no task because Gaia produces 700 million stellar sites, 150 million photometers, and 14 million spectra every day.

A torrent of raw data only human-led algorithms make them measurements that can be used by astronomers.

It will take five years to deliver this third catalog of observations from 2014 to 2017. And we will have to wait until 2030 for the final version, when Gaia will finish scanning the space, in 2025.

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