L’une des découvertes surprenantes de la version 3 des données Gaia est que Gaia est capable de détecter les tremblements d’étoiles – de minuscules mouvements à la surface d’une étoile – qui modifient la forme des étoiles, ce pour quoi l’observatoire n’avait pas été conçu à l’origine. Crédit : ESA/Gaia/DPAC, CC BY-SA 3.0 IGO
Gaia est une mission de l’Agence spatiale européenne (ESA) visant à créer une carte tridimensionnelle précise de plus d’un milliard d’étoiles à travers notre Milky Way galaxy and beyond. Although it launched all the way back in 2013, it is still working to accurately map the the motions, luminosity, temperature and composition of the stars in our galaxy.
Along the way it has made numerous discoveries, such as detecting a shake in the Milky Way, the observation of almost 500 explosions in galaxy cores, crystallization in white dwarfs, and discovering a billion-year-old river of stars. It also revealed the total weight of the Milky Way, a direct measurement of the galactic bar in the Milky Way, mysterious fossil spiral arms in the Milky Way, and a new member of the Milky Way family.
Today marks the data of the third data release from Gaia. The first data release was on September 14, 2016, followed by the second data release on April 25, 2018. On December 3, 2020, they did an early third data release with detailed data on more than 1.8 billion stars. All this data is helping to reveal the origin, structure, and evolutionary history of our galaxy.
This image shows four sky maps made with the new ESA Gaia data released on June 13, 2022. Credit: © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO
Today (June 13, 2022), ESA’s Gaia mission releases its new treasure trove of data about our home galaxy. Astronomers describe strange ‘starquakes’, stellar DNA, asymmetric motions, and other fascinating insights in this most detailed Milky Way survey to date.
Gaia is ESA’s mission to create the most accurate and complete multi-dimensional map of the Milky Way. This allows astronomers to reconstruct our home galaxy’s structure and past evolution over billions of years, and to better understand the lifecycle of stars and our place in the Universe.
Quoi de neuf dans la version 3 des données ?
La version 3 des données de Gaia contient des détails nouveaux et améliorés pour près de deux milliards d’étoiles dans notre galaxie. Le catalogue comprend de nouvelles informations, notamment les compositions chimiques, les températures stellaires, les couleurs, les masses, les âges, et la vitesse à laquelle les étoiles se rapprochent ou s’éloignent de nous (vitesse radiale). Une grande partie de ces informations a été révélée par le nouveau rapport de la Commission européenne sur l’astronomie. spectroscopie une technique dans laquelle la lumière des étoiles est divisée en ses couleurs constitutives (comme un arc-en-ciel). Les données comprennent également des sous-ensembles spéciaux d’étoiles, comme celles qui changent de luminosité au fil du temps.
Cet ensemble de données comprend également le plus grand catalogue d’étoiles binaires, des milliers d’objets du système solaire tels que les astéroïdes et les lunes des planètes, et des millions de galaxies et de quasars en dehors de la Voie lactée.
Tremblements d’étoiles
L’une des découvertes les plus surprenantes issues des nouvelles données est que Gaia est capable de détecter les tremblements d’étoiles – de minuscules mouvements à la surface d’une étoile – qui modifient la forme des étoiles, ce pour quoi l’observatoire n’avait pas été conçu à l’origine.
Auparavant, Gaia avait déjà découvert des oscillations radiales qui font gonfler et rétrécir périodiquement les étoiles, tout en conservant leur forme sphérique. Mais Gaia a maintenant repéré d’autres vibrations qui ressemblent davantage à des tsunamis à grande échelle. Ces oscillations non radiales modifient la forme globale d’une étoile et sont donc plus difficiles à détecter.
Gaia a découvert de fortes secousses non radiales dans des milliers d’étoiles. Gaia a également révélé de telles vibrations dans des étoiles qui n’ont que rarement été observées auparavant. Ces étoiles ne devraient pas avoir de tremblements de terre selon la théorie actuelle, alors que Gaia les a détectés à leur surface.
“Les tremblements d’étoiles nous apprennent beaucoup sur les étoiles, notamment sur leur fonctionnement interne. Gaia ouvre une mine d’or pour l’astérosismologie des étoiles massives”, explique Conny Aerts de la KU Leuven en Belgique, qui est membre de la collaboration Gaia.
L’ADN des étoiles
La composition des étoiles peut nous renseigner sur leur lieu de naissance et leur parcours ultérieur, et donc sur l’histoire de la Voie lactée. Avec les données publiées aujourd’hui, Gaia révèle la plus grande carte chimique de la galaxie couplée à des mouvements en 3D, de notre voisinage solaire aux plus petites galaxies qui entourent la nôtre.
Certaines étoiles contiennent plus de “métaux lourds” que d’autres. Pendant le Big Bang, only light elements were formed (hydrogen and helium). All other heavier elements – called metals by astronomers – are built inside stars. When stars die, they release these metals into the gas and dust between the stars called the interstellar medium, out of which new stars form. Active star formation and death will lead to an environment that is richer in metals. Therefore, a star’s chemical composition is a bit like its DNA, giving us crucial information about its origin.
This image shows an artistic impression of the Milky Way, and on top of that an overlay showing the location and densities of a young star sample from Gaia’s data release 3 (in yellow-green). The “you are here” sign points towards the Sun. Credit: © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO
With Gaia, we see that some stars in our galaxy are made of primordial material, while others like our Sun are made of matter enriched by previous generations of stars. Stars that are closer to the center and plane of our galaxy are richer in metals than stars at larger distances. Gaia also identified stars that originally came from different galaxies than our own, based on their chemical composition.
“Our galaxy is a beautiful melting pot of stars,” says Alejandra Recio-Blanco of the Observatoire de la Côte d’Azur in France, who is a member of the Gaia collaboration.
“This diversity is extremely important, because it tells us the story of our galaxy’s formation. It reveals the processes of migration within our galaxy and accretion from external galaxies. It also clearly shows that our Sun, and we, all belong to an ever-changing system, formed thanks to the assembly of stars and gas of different origins.”
This image shows the orbits of the more than 150,000 asteroids in Gaia’s data release 3, from the inner parts of the Solar System to the Trojan asteroids at the distance of Jupiter, with different color codes. The yellow circle at the center represents the Sun. Blue represents the inner part of the Solar System, where the Near Earth Asteroids, Mars crossers, and terrestrial planets are. The Main Belt, between Mars and Jupiter, is green. Jupiter trojans are red. Credit: © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, Acknowledgements: P. Tanga (Observatoire de la Côte d’Azur)
Binary stars, asteroids, quasars, and more
Other papers that are published today reflect the breadth and depth of Gaia’s discovery potential. A new binary star catalog presents the mass and evolution of more than 800 thousand binary systems, while a new asteroid survey comprising 156 thousand rocky bodies is digging deeper into the origin of our Solar System. Gaia is also revealing information about 10 million variable stars, mysterious macro-molecules between stars, as well as quasars and galaxies beyond our own cosmic neighborhood.
The position of each asteroid at 12:00 CEST on June 13, 2022, is plotted. Each asteroid is a segment representing its motion over 10 days. Inner bodies move faster around the Sun (yellow circle at the center). Blue represents the inner part of the Solar System, where the Near Earth Asteroids, Mars crossers, and terrestrial planets are. The Main Belt, between Mars and Jupiter, is green. The two orange ‘clouds’ correspond to the Trojan asteroids of Jupiter. Credit: © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, Acknowledgements: P. Tanga (Observatoire de la Côte d’Azur)
“Unlike other missions that target specific objects, Gaia is a survey mission. This means that while surveying the entire sky with billions of stars multiple times, Gaia is bound to make discoveries that other more dedicated missions would miss. This is one of its strengths, and we can’t wait for the astronomy community to dive into our new data to find out even more about our galaxy and its surroundings than we could’ve imagined,” says Timo Prusti, Project Scientist for Gaia at ESA.
