Gaia Completes Its Milky Way Scan

Image from BSC

The Completion of a Ten-Year Mission

On 17 January 2025 the Gaia mission of the European Space Agency (ESA) finished its main sky-scanning phase after monitoring over two billion stars and other objects for ten years.

The spacecraft's fuel was running nearly out and thus its scanning campaign officially ended. Although the mission is in a retired orbit and data processing will continue for years, active observing is finished.

Gaia's data have revolutionized our understanding of the structure, motion and composition of the Milky Way. With trillions of individual measurements and high-precision astrometry the mission provided unprecedented maps of stellar positions and motions. These data form the basis for a wide variety of astrophysical investigations ranging from star formation to galactic dynamics.

Retirement of the mission is a milestone for astrometry: the measurement of observing positions and motions of celestial objects. Gaia's legacy will be carried on by future missions, but the dataset is already a game-changing asset for astronomy. The era of galactic-scale high-fidelity maps is here.

Implications and Future Leaps

Now that Gaia has observed, the challenge now is to read and excavate the information. Subsequent releases, a large release since 2016, will provide refined catalogs for scientists to probe. Gaia's finished sweep clears the way for next-generation missions even more grand in scope and precision.

With astrometry of this fine precision available, scientists will be measuring finer structure within the galaxy: stellar streams, dark matter structure, stellar sub-populations, and galactic collisions long past. The rich harvest will enable cross-astronomy working in astronomy ranging from exoplanet detection to time-domain astronomy. Further Gaia data provide a foundation for better navigation and space modeling within our galaxy.

For the public it is a sign that mapping the universe is not the exclusive domain of fantastical science fiction but a real, systematic endeavor. The stars visible to us overhead have now been quantified with precision never before imagined, and our place in the galaxy is being mapped out with precision.