Gaia
Gaia — ESA's astrometry observatory, which charted the positions and motions of nearly two billion stars from an orbit around the Sun–Earth L2 point, about 1.5 million km from Earth. Science observations ended on 15 January 2025; on 27 March 2025 a last thruster burn moved it off L2 into a heliocentric disposal orbit, and it was switched off. Its position is JPL Horizons': at L2 until then, and on that orbit since.
Key facts
Mission & specifications
Mission
- Operator
- ESA
- Launched
- December 19, 2013
- Status
- Completed
Trajectory
- Speed rel. Earth
- 17.5 km/s
- Computed from the cached state vector, relative to Earth
- Distance from the Sun
- 1.07 AU
- Computed from the cached position
- Distance from Earth
- 0.663 AU
- Computed from cached positions
- Distance from Venus
- 0.614 AU
- Computed from cached positions
Mission
Gaia built the most precise map of our galaxy ever made. Launched by the European Space Agency on 19 December 2013 and stationed at the Sun–Earth L2 point, the spacecraft spent more than a decade slowly spinning, sweeping two telescopes across the whole sky again and again to pin down the positions, distances, motions, brightness and colours of nearly two billion stars. Its measurements are staggeringly fine — angles of a few millionths of an arcsecond, equivalent to spotting a coin on the Moon — achieved with a billion-pixel camera, the largest ever flown in space. By measuring the tiny annual wobble of each star caused by Earth's own motion around the Sun, Gaia turned a flat picture of the heavens into a true three-dimensional chart, tracing the structure, history and hidden streams of the Milky Way. Its successive data releases reshaped nearly every field of astronomy, from the search for exoplanets and the weighing of black holes to evidence of ancient galaxies the Milky Way once swallowed. Gaia also catalogued asteroids, distant quasars and millions of galaxies along the way. Having exhausted the propellant needed to keep scanning, the mission concluded its observations on 15 January 2025. On 27 March a last thruster burn moved Gaia off L2 into an orbit around the Sun, and it was switched off. Its archive — the foundation for star maps and discoveries for generations — will be mined long into the future.
- 2013Launch toward L2, a stable spot beyond Earth's shadowLaunch
A Soyuz rocket sends Gaia to the Sun–Earth L2 point to begin charting the galaxy.
- 2014Routine sky scanning beginsMilestone
Gaia starts spinning slowly, sweeping its twin telescopes across the whole sky.
- 2016First data releaseMilestone
Positions and brightness for over a billion stars are published, the first instalment of the map.
- 2018Second data releaseMilestone
Precise distances and motions for 1.3 billion stars transform nearly every field of astronomy.
- 2022Third data releaseMilestone
A vast new catalogue adds chemistry, binaries, asteroids and more to the galactic map.
- 2025End of sky-scanningMilestone
With its propellant spent, Gaia stops observing after more than a decade of mapping.
- 2025Retired to an orbit around the SunMission end
A last thruster burn moves Gaia off L2 into a heliocentric disposal orbit, and it is switched off. According to JPL Horizons it comes back to Earth's vicinity every 14 years, at a distance of about 10 million km.
Images
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