On Monday, June 13, 2022, the Gaia mission releases a new catalog, containing data for nearly two billion stars in our galaxy. 450 scientists from 20 countries are coordinating their efforts to process and make usable the billions of raw data collected on our galaxy by ESA’s Gaia satellite since its launch in 2013. France is the first contributor to the Gaia mission. Scientists from Paris Observatory - PSL participate very actively, with two key responsibilities in Gaia DR3: the processing and analysis of Gaia’s spectrograph data and those of the star systems (double or multiple).
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 release 3?
Gaia’s data release 3 contains new and improved details for almost two billion stars in our galaxy. The catalogue includes new information including chemical compositions, stellar temperatures, colours, 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 colours (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 catalogue 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.
Gaia data release 3: exploring our multi-dimensional Milky Way
Images
The Milky Way of Gaia in motion
ESA’s Gaia data version 3 shows us the speed at which more than 30 million objects in the Milky Way (mostly stars) are moving towards or away from us. This is called the "radial velocity". We can now see how the objects are moving across a large part of the Milky Way disk.
The rotation of the disk, projected along the line of sight, can be seen by alternating bright areas (moving away from us) and dark areas (moving toward us). Several objects whose radial velocity differs from that of their close environment are visible by contrast.
The Large and Small Magellanic Clouds (LMC and SMC) appear as bright spots in the lower right corner of the image. The Sagittarius dwarf galaxy is visible as a faint quasi-vertical band below the Galactic Center.
Several globular clusters appear as tiny dots in the image, such as 47 Tucanae, the dark dot immediately to the left of SMC.
The third release of ESA’s Gaia data shows us how fast more than 30 million stars in the Milky Way are moving toward or away from us. This is called the "radial velocity", which is the third dimension of velocity in the Gaia map of our galaxy. With the proper motions of the stars (motion in the sky), we can now see how the stars are moving over a large part of the Milky Way.
This sky map shows the velocity field of the Milky Way for 26 million stars. The colors show the radial velocities of the stars along the line of sight. Blue shows the parts of the sky where the average motion of the stars is approaching us and red shows the regions where the average motion is moving away from us. The lines visible in the figure trace the motion of the stars projected onto the sky (proper motion). These lines show how the direction of the speed of the stars varies with the galactic latitude and longitude. The Large and Small Magellanic Clouds (LMC and SMC) are not visible because only stars with well-defined distances have been selected to make this image.
ESA’s Gaia mission not only maps the stars in our galaxy, it also tells us what lies between the stars. The space between stars is not empty, but filled with clouds of dust and gas, from which stars are born.
The composition of stars can tell us about where they were born and where they went from there, and thus about the history of the Milky Way. With the release of today’s data, Gaia brings us a chemical map of the galaxy.
This image shows an artistic impression of the Milky Way, and on top of it, an overlay showing the location and densities of a sample of young stars from the Gaia version 3 data (in yellow-green). The "you are here" sign points to the Sun.
This image shows the orbits of more than 150,000 asteroids in version 3 of the Gaia data, from the inner parts of the solar system to Trojan asteroids at the distance of Jupiter, with different color codes. The yellow circle in the center represents the Sun. The blue represents the inner part of the solar system, where the near-Earth asteroids, the Mars transits and the terrestrial planets are located. The main belt, between Mars and Jupiter, is green. The trojans of Jupiter are red.
The position of each asteroid at 12:00 CEST on June 13, 2022 is plotted. Each curve segment shows the movement of an asteroid over 10 days. The inner bodies are moving faster around the Sun (yellow circle in the center). Blue represents the inner part of the solar system, where near-Earth asteroids, Mars crossings and terrestrial planets are located. The main belt, between Mars and Jupiter, is in green. The two orange "clouds" correspond to the Trojan asteroids of Jupiter.
