Terremoti! La navicella spaziale Gaia vede strane stelle nella più dettagliata indagine sulla Via Lattea fino ad oggi

Gaia è la missione dell’Agenzia spaziale europea (ESA) per creare un’accurata mappa 3D di oltre un miliardo di stelle in tutto[{” attribute=””>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.

Cosa c’è di nuovo nella versione dati 3?

Il rilascio dei dati di Gaia 3 contiene dettagli nuovi e migliorati di quasi due miliardi di stelle nella nostra galassia. Il catalogo include nuove informazioni tra cui composizioni chimichetemperature stellari, colori, masse, età e velocità con cui le stelle si avvicinano o si allontanano da noi (velocità radiale). Gran parte di queste informazioni è stata rivelata dal nuovo rilascio Spettroscopia Data, una tecnologia in cui la luce delle stelle è suddivisa nei suoi colori componenti (come un arcobaleno). I dati includono anche sottoinsiemi speciali di stelle, come quelle che cambiano la luminosità nel tempo.

Un’altra novità in questo set di dati è il più grande catalogo fino ad oggi di stelle binarie, migliaia di oggetti del Sistema Solare come asteroidi e lune planetarie e milioni di galassie e quasar al di fuori della Via Lattea.

terremoti

Una delle scoperte più sorprendenti che emergono dai nuovi dati è che Gaia è in grado di rilevare terremoti stellari – minuscoli movimenti sulla superficie di una stella – che cambiano la forma delle stelle, qualcosa per cui l’osservatorio non è stato originariamente costruito.

In precedenza, Gaia aveva già riscontrato oscillazioni radiali che fanno sì che le stelle si gonfino e si contraggano periodicamente, pur mantenendo la loro forma sferica. Ma Gaya ha ora rilevato anche altre vibrazioni che assomigliano molto a uno tsunami su larga scala. Queste oscillazioni non radiali alterano la forma globale della stella e sono quindi difficili da rilevare.

Gaia ha trovato forti terremoti non radiali in migliaia di stelle. Gaia ha anche rilevato tali vibrazioni nelle stelle che erano state viste raramente prima. Queste stelle non dovrebbero avere terremoti secondo la teoria attuale, mentre Gaia le ha rilevate sulla loro superficie.

“I terremoti ci insegnano molto sulle stelle, in particolare sul loro funzionamento interno. Gaia apre una miniera d’oro per la scienza stellare di massa”, afferma Connie Aerts di KU Leuven in Belgio, un membro della collaborazione Gaia.

DNA stellare

Il materiale di cui sono fatte le stelle può raccontarci dove sono nate e il loro prossimo viaggio, e quindi sulla storia della Via Lattea. Con il rilascio dei dati di oggi, Gaia rivela la più grande mappa chimica della galassia unita ai movimenti 3D, dal nostro vicinato solare alle galassie più piccole intorno a noi.

Alcune stelle contengono più “metalli pesanti” di altre. durante[{” attribute=””>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.