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19 December 2013
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Lagrange point 2
Astrophysics survey
What sets Gaia apart is its vast all-sky survey enabled by exceptional spacecraft stability. It has provided precise positions and motions of two billion stars relative to a quasar-based reference frame, curating the most accurate stellar catalogue to date. Through key data releases, the scientific community has open access to Gaia’s unrivalled catalogue, fuelling discovery both within and beyond astronomy. The mission is shedding light on stellar evolution, probing dark matter distribution, refining the cosmic distance ladder, exploring the dynamics of our Solar System, and even contributing to fundamental physics.
Animation of the Gaia spacecraft. Credit: ESA/Gaia/DPAC, Stefan Payne-Wardenaar.
We want to uncover the secrets of the Milky Way by studying its stars and their behaviour:
Measure positions and distances of stars:
What is the structure of the Milky Way?
Trace the motions of stars within our galaxy:
What are the kinematics of the Milky Way?
Determine the ages and properties of stars
How does the Milky Way evolve?
Gaia used three instruments to measure with great precision the positions, motions, and distances of stars (astrometry), their brightness and variability (photometry), and their compositions and light-of-sight velocities (spectroscopy). Gaia’s telescopes, with their ten mirrors, focused and directed light coming from two distinct directions onto the three science instruments, which were housed inside a protective tent within the payload module.
By observing stars repeatedly from its orbit around the second Lagrange point, Gaia built a dynamic multi-dimensional map of the galaxy, revealing its structure, history, and evolution. As a true survey mission, Gaia continuously scanned the sky, observing on average more than 800 objects per second.
Credit: ESA. Instrument list: Astrometric instrument (ASTRO), Photometric instrument (BP/RP), Radial Velocity Spectrometer (RVS).
Gaia builds on the legacy of Hipparcos, ESA’s first mission dedicated to mapping the stars. While Hipparcos charted over two million stars, Gaia increased that number by a factor of a thousand and improved positional accuracy by a factor of a hundred. Together, these missions have established and reinforced Europe’s leadership in astrometry. Looking ahead, the Milky Way has been recommended as a key theme in ESA’s Voyage 2050 programme, paving the way to extend this legacy into the next generation of astrometry missions.
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15 January 2025
Artist's impression of Gaia's launcher. Credit: ESA - D. Ducros
Gaia is a fully European mission, built and operated by ESA. ESA works closely with the Gaia Data Processing and Analysis Consortium (DPAC) comprising over 400 scientists and engineers from across Europe, and responsible for processing the raw data and converting them into the Gaia catalogues that are published in the ESA space science archives. ESA selected Airbus as prime contractor for the construction of the satellite.
Animation and sonification of star oscillations. Credit: ESA/Gaia/DPAC/Dr. Joey Mombarg, KU Leuven, Belgium
A surprising discovery coming out of Gaia's data was the ability to detect starquakes – tiny motions on the surface of the star that change the star's shape – something that the observatory was not originally built for.
Those nonradial oscillation modes cause a star's surface to move while it rotates, as shown in the animation. Dark patches are slightly cooler than bright patches, giving rise to periodic changes in the brightness of the star. The frequency of the rotating and pulsating stars was increased 8.6 million times to shift them into the audible range of humans.
In 2024, Gaia faced a double dose of trouble. First, a micrometeoroid hit the spacecraft at high speed, damaging the spacecraft’s protective cover. Then, a vital sensor which helped confirmed the detection of stars failed. These unexpected events could have signaled the end of Gaia. Instead, the mission team at ESA, the industrial partners who built Gaia, and the dedicated scientists of the Gaia Consortium worked hand-in-hand to steady the ship. This is a real-world example of how science, engineering and collaboration came together to keep one of ESA’s most ambitious missions going strong.
Explore a subset of the ESA Science Programme missions here. Additional mission pages are in progress.
The currently available mission pages are ESA's flagship missions launched from 2013 and to be launched (L-class), and the ones in development (M- and F-class).
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