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.
Gaia's data release 3 contains new and improved details for almost two
billion stars in our galaxy. The catalog includes new information including
chemical compositions, stellar temperatures, colors, masses, ages, and the
speed at which stars move towards or away from us (radial velocity). Much of
this information was revealed by the newly released spectroscopy data, a
technique in which the starlight is split into its constituent colors (like
a rainbow). The data also includes special subsets of stars, like those that
change brightness over time.
Also new in this data set is the largest catalog yet of binary stars,
thousands of solar system objects such as asteroids and moons of planets,
and millions of galaxies and quasars outside the Milky Way.
Starquakes
One of the most surprising discoveries coming out of the new data is that
Gaia is able to detect starquakes—tiny motions on the surface of a star—that
change the shapes of stars, something the observatory was not originally
built for.
Previously, Gaia already found radial oscillations that cause stars to swell
and shrink periodically, while keeping their spherical shape. But Gaia has
now also spotted other vibrations that are more like large-scale tsunamis.
These nonradial oscillations change the global shape of a star and are
therefore harder to detect.
Gaia found strong nonradial starquakes in thousands of stars. Gaia also
revealed such vibrations in stars that have seldomly been seen before. These
stars should not have any quakes according to the current theory, while Gaia
did detect them at their surface.
"Starquakes teach us a lot about stars, notably their internal workings.
Gaia is opening a goldmine for 'asteroseismology' of massive stars," says
Conny Aerts of KU Leuven in Belgium, who is a member of the Gaia
collaboration.
The DNA of stars
What stars are made of can tell us about their birthplace and their journey
afterwards, and therefore about the history of the Milky Way. With today's
data release, Gaia is revealing the largest chemical map of the galaxy
coupled to 3D motions, from our solar neighborhood to smaller galaxies
surrounding ours.
Some stars contain more "heavy metals" than others. During the 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.
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."
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.
"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.
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.
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Space & Astrophysics