The European Space Agency's Milky Way-mapper Gaia has completed the sky-scanning phase of its mission, racking up more than three trillion observations of about two billion stars and other objects over the last decade to revolutionise the view of our home galaxy and cosmic neighbourhood.
Launched on 19 December 2013, Gaia's fuel tank is now approaching empty - it uses about a dozen grams of cold gas per day to keep it spinning with pinpoint precision. But this is far from the end of the mission. Technology tests are scheduled for the weeks ahead before Gaia is moved to its 'retirement' orbit, and two massive data releases are tabled for around 2026 and the end of this decade, respectively.
"Today marks the end of science observations and we are celebrating this incredible mission that has exceeded all our expectations, lasting for almost twice its originally foreseen lifetime," said ESA Director of Science Carole Mundell.
"The treasure trove of data collected by Gaia has given us unique insights into the origin and evolution of our Milky Way galaxy, and has also transformed astrophysics and Solar System science in ways that we are yet to fully appreciate. Gaia built on unique European excellence in astrometry and will leave a long-lasting legacy for future generations."
"Today marks the last day of science data collection from Gaia, these observations to form part of the final data release," said Dr Nicholas Walton from Cambridge's Institute of Astronomy, lead of the UK Gaia Project team and ESA Gaia Science Team member. "Our Gaia team in the UK is now working hard on the incredibly complex data analysis for the upcoming Gaia data releases. These will enable a wealth of new discovery, adding to the science from one of the world's most productive science discovery machines."
Gaia delivers best Milky Way map
Gaia has been charting the positions, distances, movements, brightness changes, composition and numerous other characteristics of stars by monitoring them with its three instruments many times throughout the mission.
This has enabled Gaia to deliver on its primary goal of building the largest, most precise map of the Milky Way, showing us our home galaxy like no other mission has done before.
Gaia's repeated measurements of stellar distances, motions and characteristics are key to performing 'galactic archeology' on our Milky Way, revealing missing links in our galaxy's complex history to help us learn more about our origins. From detecting 'ghosts' of other galaxies and multiple streams of ancient stars that merged with the Milky Way in its early history, to finding evidence for an ongoing collision with the Sagittarius dwarf galaxy today, Gaia is rewriting the Milky Way's history and making predictions about its future.
Warning! More ground-breaking science ahead
The Gaia scientific and engineering teams are already working on the preparations for Gaia Data Release 4 (DR4), expected in 2026.
"This is the Gaia release the community has been waiting for, and it's exciting to think this only covers half of the collected data," said Antonella Vallenari, Deputy Chair of DPAC based at the Istituto Nazionale di Astrofisica (INAF), Astronomical Observatory of Padua, Italy. "Even though the mission has now stopped collecting data, it will be business as usual for us for many years to come as we make these incredible datasets ready for use."
"Over the next months we will continue to downlink every last drop of data from Gaia, and at the same time the processing teams will ramp up their preparations for the fifth and final major data release at the end of this decade, covering the full 10.5 years of mission data," said Rocio Guerra, Gaia Science Operations Team Leader based at ESA's European Space Astronomy Centre (ESAC) near Madrid in Spain.
Gaia's retirement plan
While today marks the end of science observations, a short period of technology testing now begins. The tests have the potential to further improve the Gaia calibrations, learn more about the behaviour of certain technology after ten years in space, and even aid the design of future space missions.
After several weeks of testing, Gaia will leave its current orbit around Lagrange point 2, 1.5 million km from the Earth in the direction away from the Sun, to be put into its final heliocentric orbit, far away from Earth's sphere of influence. The spacecraft will be passivated on 27 March 2025, to avoid any harm or interference with other spacecraft.
Wave farewell to Gaia
During the technology tests Gaia's orientation will be changed, meaning it will temporarily become several magnitudes brighter, making observations through small telescopes a lot easier (it won't be visible to the naked eye). A guide to locating Gaia has been set up here, and amateur astronomers are invited to share their observations.
"Gaia will treat us with this final gift as we bid farewell, shining among the stars ahead of its well-earned retirement," said Uwe Lammers, Gaia Mission Manager.
"It's a moment to celebrate this transformative mission and thank all of the teams for more than a decade of hard work operating Gaia, planning its observations, and ensuring its precious data are returned smoothly to Earth."
Adapted from a European Space Agency press release.
