Earthquakes! Gaia spacecraft sees strange stars in most detailed Milky Way survey to date

One of the amazing discoveries coming out of the Gaia 3 data release is that Gaia is able to detect stellar earthquakes — tiny movements on a star’s surface — that change star shapes, something the observatory wasn’t originally built for. Credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO

Gaia is the mission of the European Space Agency (ESA) to create an accurate 3D map of more than a billion stars across[{” 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.

What’s new in data version 3?

The Gaia 3 data release contains new and improved details of nearly two billion stars in our galaxy. The catalog includes new information including chemical compositionsstellar temperatures, colours, masses, ages, and the speed with which stars move toward or away from us (radial velocity). Much of this information was revealed by the newly released Spectroscopy Data, a technology in which starlight is divided into its component colors (such as a rainbow). The data also includes special subsets of stars, such as those that change brightness over time.

Also new in this data set is the largest catalog to date of binary stars, thousands of Solar System objects such as asteroids and planetary moons, and millions of galaxies and quasars outside the Milky Way.

earthquakes

One of the most surprising discoveries emerging from the new data is that Gaia is able to detect stellar earthquakes — tiny movements on the surface of a star — that change the shapes of stars, something the observatory was not originally built for.

Previously, Gaia had already found radial oscillations that cause stars to periodically swell and contract, while maintaining their spherical shape. But Gaya has now also detected other vibrations that closely resemble a large-scale tsunami. These non-radial oscillations alter the global shape of the star and are therefore difficult to detect.

Gaia has found strong non-radial earthquakes in thousands of stars. Gaia also detected such vibrations in stars that had rarely been seen before. These stars should not have any earthquakes according to the current theory, while Gaia detected them on their surface.

“Starquakes teach us a lot about the stars, in particular their inner workings. Gaia opens a gold mine for massive stellar science,” says Connie Aerts of KU Leuven in Belgium, a member of the Gaia collaboration.

stellar DNA

The material that stars are made of can tell us about where they were born and their next journey, and thus about the history of the Milky Way. With the release of data today, Gaia reveals the largest chemical map of the galaxy coupled with 3D motions, from our solar neighborhood to the smaller galaxies around us.

Some stars contain more “heavy metals” than others. during the[{” 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.