The Gaia satellite was launched in 2013 to position itself 1.5 million kilometers from Earth, opposite the direction of the Sun, and scan space. Its main mission: to measure the position, distance and movement of nearly two billion stars in the Milky Way. But it has other strings to its bow and its optics have also focused on objects in the solar system, very close, up to the very luminous quasars located billions of light-years from our star.
This June 13, 2022, from 10 a.m., ESA will reveal the content of the 3th catalog (DR3) relating to the results of the analysis of data obtained over 34 months, between July 25, 2014 and May 28, 2017. A first overview (EDR3) of these had already been unveiled in December 2020 with the measurements astrometric and photometric data of 1.8 billion celestial objects in our galaxy. “Gaia has unveiled a new world of data and we will gain further precision and categorization with this next batch of results.” rejoices François Mignard, from the Observatoire de Provence and scientific manager of Gaia France.
“The Third Dimension of Space Velocity”
The DR3 will bring a multitude of new data with in particular the classification of almost all the objects in the catalog and for 500 million of them many astrophysical parameters such as temperature, gravity or even the abundance of chemical elements. Gaia has also made it possible to measure the radial velocity of 34 million stars, that is to say their speed of approach or distance from the Sun. “It’s a great leap forward that finally brings the third dimension of space speeds“explains Catherine Turon, astronomer emeritus at the Observatoire de Paris-PSL and pioneer in space astrometry. The two other dimensions measured are the speed of rotation and the tangential speed, namely the angular displacement of a star on the celestial sphere. . “Another great novelty will consist in the publication of millions of spectra obtained by the RVS [le Radial Velocity Spectrometer] and the two spectrophotometers, BP and RP, from Gaia“adds the astrophysicist.
Gaia’s different observation techniques. Credit: ESA.
“Spectrophotometry will make it possible to draw up a taxonomic classification of objects with their surface properties and to establish relationships between their colors and their dynamic properties.“says François Mignard. So much new information that will lead to numerous scientific publications. Thousands of articles have already appeared following the dissemination of DR1 (in 2016), DR2 (in 2018) and EDR3 in 2020. They made it possible to represent the Milky Way in a way that had never been possible before: in 3D and in color, but also to identify all the stars close to the Sun, to determine the acceleration of the barycenter of the solar system, to identify traces of collision between the Milky Way and another galaxy billions of years ago and much more.
“Among the novelties of this catalog, there are also data concerning more than 800,000 non-simple objects, most of which are binary stars, that is to say bodies formed of two stars of which one of the companions can be a star. of the same type, a white dwarf, a neutron star or even a black hole” underlines Alain Jorissen, astronomer at the Free University of Brussels and member of the Belgian team of the DPAC consortium (Data Processing and Analysis Consortium).
https://www.youtube.com/watch?v=BXkLtNo-aHg
Follow the publication of the 3rd Gaia catalog live from the Observatoire de Provence in Nice, from 10 a.m. on Monday June 13, 2022.
The DPAC, which is also the cornerstone of the Gaia mission: it brings together 450 scientists, software developers and data processing specialists. Its mission is to process the huge stream of data from the satellite which represents the largest amount ever processed in the history of astronomy, almost one petabyte (or 1 million billion bytes!). For this, the DPAC is divided into 8 units, each in charge of a specific area of the data analysis and reduction process and then their publication. A colossal work that explains why publications are divided into catalogs published approximately every two years. DR4 is thus expected for 2025 and the final release (which is not yet officially scheduled) should be delivered around 2030.
Small solar system bodies, exoplanets and quasars
If the stars of the Milky Way are the main target of Gaia, the telescope which scans the entire sky is also interested in a close neighbour: the Andromeda galaxy whose photometric survey will be published. And much further there are some 2.9 million galaxies and 1.9 million quasars, these active galactic nuclei hosting a supermassive black hole in their center, for which we will have new information. Finally, “we will also discover for the first time detailed information on the small bodies of the solar system, moons and asteroids“adds François Mignard.
No less than 155,000 of them have been sifted through, from the closest that could threaten Earth to the furthest that revolve far beyond the dwarf planet Pluto. With for each of the characteristics of luminosity, colors or composition. More than enough to occupy specialists for many years. Science and Future will come back in more detail on certain aspects of the Gaia catalog very soon.
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