The European Space Agency’s Gaia mission has completed one of its main tasks: delivering a map of the Milky Way galaxy, consisting of trillions of observations taken over 10 years of space.
Between July 24, 2014 and today, Gaia has made more than three trillion observations of the two billion stars and other objects in our galaxy. The result of the spacecraft’s efforts is nothing less than the largest, most accurate map of our galaxy to date. The job is done, and as the spacecraft runs out of fuel, Gaia is now slated for retirement.
The wealth of data collected by Gaia has allowed scientists to create the best reconstructed view of what our galaxy might look like to an outside observer; the reconstruction from the edge is above, and the view from the face below.
Gaia’s data revealed that the Milky Way has more than two spiral arms, which are less prominent than previously thought. The brighter spot at the center of the galaxy is the galactic bulge (which looks more prominent in the image above), where resides in Sagittarius A*supermassive black hole.
Gaia data has revealed a host of intriguing objects in our galaxy; in April 2024, scientists discovered the most massive black hole of stellar mass in the Milky Way, only 2000 light years from Earth. (In 2022, Gaia data included the known black hole closest to Eartha relatively small compact object only 1,600 light-years away.)
In June last year, examination of Gaia data showed that interactions between the Milky Way and another galaxy may have occurred billions of years later than previously thought, shaking up theories about the evolution of our galaxy.
“Gaia has changed our impression of the Milky Way,” said Stefan Payne-Wardenaar, a scientific visualizer for the Haus der Astronomie in Germany, in press release. “Even basic ideas have been revised, such as the rotation of our galaxy’s central bar, the curvature of the disk, the detailed structure of the spiral arms and the interstellar dust near the Sun.”
Among the spacecraft’s many accomplishments: Gaia has precisely measured the orbits of more than 150,000 asteroids and produced a three-dimensional map of more than a million quasars, the largest of its kind.
“The distant parts of the Milky Way remain educated guesses based on incomplete data,” Payne-Wardenaar added. As more Gaia data becomes available, “our view of the Milky Way will become even more precise,” he said.
The spacecraft is now almost out of fuel; when her tank is fully depleted, Gaia will be moved into a retreat orbit. In the coming weeks, Gaia will undergo several technology tests that will prepare the spacecraft for that final orbit.
But the story of the spacecraft will live on after the observation ends. The mission is expected to release its next data next year, with another data release scheduled for the end of the decade. Gaia has produced 500 terabytes of data so far—that’s just 5.5 years of the spacecraft’s observations.
“After 11 years in space and surviving micrometeorite collisions and solar storms along the way, Gaia has finished collecting scientific data,” said Johannes Sahlmann, Gaia Project Scientist, at ESA rid. “All eyes are now on preparing the next data releases.” At least 500 terabytes of data are expected to be released in the data dump next year, which could include data on new exoplanets and binary star systems.
Gaia will be passivated—made electrically inert—27. March, to mitigate any interference between the veteran mission and other spacecraft still in operation.