Retirement for space veteran: Gaia Observatory stops scientific observations

The Gaia Space Observatory has completed its science program. It will be used for technology tests in the coming weeks, after which it will be moved to disposal orbit. 

Gaia telescope in an artist’s impression. Source: ESA/ATG medialab; Milky Way: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO. Acknowledgement: A. Moitinho

Gaia’s main achievements

The Gaia observatory was launched by ESA at the end of 2013. Its key mission was to make a detailed map of the Milky Way. During its work, it observed 2 billion stars and other objects, measuring their brightness, distance, and direction of motion. This made it possible to create an unparalleled map of our home galaxy, which has forced astronomers to rethink many old ideas about it. In addition, Gaia managed to detect clusters of ancient stars and remnants of other galaxies, shedding light on the history of the Milky Way.

A map of the Milky Way created from Gaia telescope data (annotated version). Source: ESA/Gaia/DPAC, Stefan Payne-Wardenaar

But Gaia’s achievements don’t stop there. Over the years, the telescope has discovered many objects, from asteroids in our Solar System to distant galaxies and quasars. For example, the space observatory has determined the orbits of more than 150,000 asteroids with high precision and has made such high-quality measurements that it has discovered possible satellites for hundreds of them. Gaia also created the largest 3D map of about 1.3 million quasars (galaxies with extremely active black holes at their centers). The most distant ones are so far away that we see them at times when the age of the Universe was only 1.5 billion years old. 

Estimated appearance of the Milky Way, modeled from Gaia data. Source: ESA/Gaia/DPAC, Stefan Payne-Wardenaar

Gaia also discovered a new type of black hole — including a black hole with a mass nearly 33 times that of the Sun. It hides in the constellation Aquila less than 2,000 light-years from Earth. The telescope has also discovered several exoplanets and hypervelocity stars leaving our Milky Way. In total, Gaia has collected 500 terabytes of data over the course of its operation.

Retirement for space observatory

Gaia has encountered various problems several times over the years of service. The most serious incident occurred in April 2024, when a micrometeoroid hit the telescope. But that’s not the reason Gaia stopped working. Cold nitrogen was used to precisely aim the telescope. It had a total of 55 kilograms of this gas on board. In more than a decade of service, it performed 15,300 guidance maneuvers, nearly exhausting all available supplies. Because of this, ESA had to decide to end the mission’s science program. On January 15, 2024, Gaia made its last scientific observations. 

Infographic highlighting the major achievements of the Gaia telescope. Source: ESA/Gaia/DPAC, Milky Way impression by Stefan Payne-Wardenaar

But Gaia’s work doesn’t stop there. In the next few weeks, the telescope will be involved in technological tests. They will allow engineers to study the behavior of its components and instrumentation in more detail. This data can help improve Gaia’s calibrations and will also be used by designers of future space missions.

Once the tests are completed and all data is transmitted to Earth, Gaia will leave orbit around the L2 Lagrangian point and be placed into a final heliocentric orbit away from Earth’s sphere of gravitational influence. Eventually, the spacecraft will be passivated in March-April 2025, after which communication with it will be terminated.

According to ESA

Advertising