Gaia’s massive third data release is out!

It’s here! The ESA’s third and largest data release (DR3) Gaia Observatory has been officially made public. As promised, the DR3 contains new and improved details for nearly two billion stars in our galaxy, including the chemical composition, temperatures, colors, masses, ages and the speeds at which stars move. The release coincided with a virtual press event hosted by the Gaia . Data Processing and Analysis Consortium (DPAC) on June 13, with ESA officials and guest speakers discussing the importance of the new data.

Much of this information consists of newly released spectroscopy data, a technique in which starlight is broken down into the color spectrum and analyzed to determine how it is shifted. This technique is known as radial speed (also known as Doppler spectroscopy), where light is shifted toward the red or blue end of the spectrum (i.e., redshift and blueshift) based on whether the object is moving toward or away from Earth (respectively). Astrophysicists use this technique to determine how a star moves relative to ours and also because of detect exoplanets

These findings were described in a series of articles co-published with the DR3, which provide an overview of the Gaia mission, the contents of DR3, summarizes details about the technicalities, raw data processing and calibration, and the paths taken to get to DR3. These articles were published in a special issue of Astronomy and Astrophysics and were made available on the ESA’s website

The latest release also includes data on special subsets of stars, such as those that undergo changes in brightness over time (known as variable stars). The DR3 also contained the largest catalog of binary star systems, thousands of objects in the solar system (asteroids and moons), and millions of galaxies and quasars outside the solar system (such as Andromeda). Other important discoveries include the ability of Gaia to detect small movements on the surface of a star (Starquakes) and improved data on the chemical composition of stars.


As the name suggests, starquakes are a phenomenon in which a star’s crust undergoes a sudden adjustment that changes shape. This came as a surprise to astronomers, as the observatory was not originally built. Earlier, Gaia data pointed to radial oscillations that cause stars to swell and shrink periodically, but leave their shape unaffected. The latest data shows that: Gaia can also detect non-radial oscillations that are much more powerful but more difficult to detect because they change the shape of the star globally.

Gaia discovered strong non-radial starquakes on the surfaces of thousands of stars, even where conventional theory says none should exist. Just as earthquakes and similar phenomena on other bodies (such as “moonquakes and “marsquakes” that have been studied) allow astronomers to learn more about the interiors of planets and moons, these starquakes can tell astronomers a lot about the inner workings of different star types. As the research papers indicate, this information could open up new opportunities for the field of “asteroseismology.”

Stellar DNA

By studying the chemical makeup of stars, astronomers can put stricter restrictions on where the stars were born and how they migrated over time. This, in turn, can reveal interesting details about the Milky Way’s history and how it has evolved since then. With the DR3, Gaia has revealed the largest chemical map of the galaxy, from our solar system to smaller galaxies around the Milky Way. Combined with proper motion and velocity measurements (astrometry) in the catalog, this information has provided a 3D map of where stars formed and got to where they are today.

The most important aspect of stellar composition is the amount of heavy metals they contain, otherwise known as ‘metallicity’. The first stars in the universe, formed about 100 million years after the Big Bang, were composed of hydrogen and helium, reflecting the composition of the universe at that time. These Population III stars (as they are called) formed heavier elements within them through a slow process of nuclear fusion, where fusion and helium combined to create boron, carbon, nitrogen, oxygen, silicon and finally iron.

When these stars collapsed at the end of their life cycles and exploded in huge supernovae, these elements were dispersed through the interstellar medium (ISM) – from which new stars were formed. This active cycle of star formation and death has slowly enriched the interstellar medium with metals over time. Subsequent generations of stars, known as Population II and I, contain increasing amounts of these elements, which can be used to determine their age. In this regard, a star’s chemical makeup is similar to its DNA, as it can provide crucial information about its origin.

With this latest release Gaia has revealed that some stars in our galaxy are “metal-poor” and composed of primordial material, while others (like our sun) are rich in metal. The data also showed that stars closer to the center and flat of our galaxy have higher metallicities than those farther from the center and outside the galactic disk. Based on their compositions, Gaia also identified numerous stars that formed in different galaxies but were captured by the Milky Way or become part of it through galactic mergers.

Alejandra Recio-Blanco, astronomer at the Observatoire de la Côte d’Azur and member of the Gaia Collaboration, explained

“Our galaxy is a beautiful melting pot of stars. This diversity is extremely important, as it tells us the story of the formation of our galaxy. It reveals the processes of migration within our galaxy and accretion of 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 origin.”

Other findings

Other research papers released alongside the DR3 detail numerous other discoveries, highlighting the vast potential of the Gaia mission. In particular, the new binary star catalog (the largest ever) contains data on the masses and evolution of more than 800,000 binary star systems. Another breakthrough is a new asteroid study that provides data on the origin of 156,000 thousand rock bodies in our solar system. last, Gaia‘s observations have revealed about 10 million variable stars, macromolecules in the ISM, and quasars and galaxies. said Timo Prusti, Gaia Project scientist at the ESA:

“Unlike other missions that target specific objects, Gaia is a fact-finding mission. This means that while we examine the entire sky multiple times with billions of stars, Gaia will undoubtedly 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 learn even more about our galaxy and its environment than we could have imagined.”

Additional releases are planned, the date of which will depend on future mission expansions. The mission has been approved until the end of 2022 and there are indications that it will be extended further until 2025. In that case, the full data release for the five-year nominal mission (DR4) will take place before the extended mission comes to an end and DR5 – which will contain data of the full ten-year term – will be released no earlier than three years after the end of the mission.

This finished product contains the most accurate astronomical measurements ever made and includes:

  • Complete Astrometric, Photometric and Radial Velocity Catalogs
  • All available variable and non-single star solutions
  • Source classifications (probabilities) plus multiple astrophysical parameters (derived from BP/RP, RVS and astrometry) for stars, unresolved binaries, galaxies and quasars. Some parameters may not be available for faint(er) stars
  • A list of exoplanets
  • All epoch and transit data for all sources

All this information is made available free of charge to researchers and the general public through the ESAs Gaia Data release schedule† The Gaia Data Processing and Analytics ConsortiumThe public outreach working group is also collaborating with the Astronomical Calculation Institute (ARI) at the University of Heidelberg develop Gaia Sky – was developed to explore the galaxy in three dimensions using Gaia data.

Read further: ESA

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