Mission Accomplished for Space Telescope Gaia, but many Years of Data Analysis Remain

Gaia is a space telescope onboard a satellite that has circulated the Sun during 11 years. With the help of astrometry, which is a technique to measure the positions, distances and movements of stars and other heavenly bodies, Gaia has been able to measure distances and luminosities for up to 2 billion stars, which is about one percent of all stars in the Milky Way.

The Gaia mission was originally supposed to last five years, but thanks to the fact that it has been so successful, it has been extended in two rounds.

"The Gaia mission has been the most successful ESA mission ever if you look at the number of publications. There are around five publications per day based on data from Gaia", says Andreas Korn, who is one of the researchers at Uppsala University that works with Gaia.

The three-dimensional map that Gaia created, helps to write the history of the Milky Way and Gaia’s data is a treasure trove for future observations and discoveries.

Until now, we have, among other things, discovered moons orbiting asteroids in our solar system, black holes 30 times heavier than the Sun, and how our solar system moves around the centre of the Milky Way, how many spiral arms the Milky Way has and what the bar in the middle looks like.

"Gaia has discovered very different things, among others a galaxy that collided with the Milky Way around ten billion years ago. It has been named Gaia-Enceladus, after the mythological son of Gaia", says Andreas Korn.

As opposed to for example the Hubble telescope and the James Webb telescope, Gaia has not observed specific objects, but instead observed the entire sky through a rotation of the telescope’s field of view. In that way, all celestial positions have been able to be observed repeatedly, up to 200 times. Data from Gaia has also been a prerequisite for, for example, the observations that the James Webb telescope has recently been able to make.

Andreas Korn and Ulrike Heiter, both senior lecturers at the Division of Astronomy and Space Physics at the Department of Physics and Astronomy, have worked with Gaia during 18 years. They are members of the European collaboration Data Processing and Analysis Consortium (DPAC), with 400 researchers that analyse Gaia’s data, which is made public in various data releases.

Uppsala University’s part in the Gaia projects is to analyse data for the most common stars in the Milky Way. Uppsala University has a 40-year history of developing models of this type of stars, which like the Sun have a surface temperatures of around 6000 degrees Celsius, but also of colder objects, so called M-dwarfs.

"We work mostly with the astrophysical part of the Gaia project, that is with parameters such as surface temperature, mass and composition that can be deducted from Gaia’s data. Our work makes sure that no physically incorrect data are released", says Andreas Korn.

On January 15, 2025, the Gaia observations were stopped because the fuel that steers the satellite in the orbit around the Sun will soon run out. Gaia has been moving in an orbit around the Sun, around Lagrange point 2 (L2), 1.5 million kilometers outside the Earth’s orbit. L2 follows the Earth around the Sun and is the best observation point, and it is also from here the James Webb telescope observes.

With Gaia’s retirement, the telescope itself is being shut down, but the satellite continues orbiting the Sun, but far from L2, as we only want to have active satellites at L2.

No new scientific data will be gathered by Gaia, but the researchers continue the data analysis of already collected data for several more years and new data releases are planned for 2026 and 2032.

Camilla Thulin

English translation: Johan Wall