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 (Gaia DR4 and DR5) are tabled for around 2026 and the end of this decade, respectively. The last data release to this day (Gaia DR3) took place in June 2022, and the data can be accessed using CDS tools.
“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,” says 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.”
“After 11 years in space and surviving micrometeorite impacts and solar storms along the way, Gaia has finished collecting science data. Now all eyes turn towards the preparation of the next data releases,” says Gaia Project Scientist Johannes Sahlmann.
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 over the course of 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.
As such, we now also have the best reconstructed view of how our galaxy might look to an outside observer. This new artist impression of the Milky Way incorporates Gaia data from a multitude of papers over the past decade.
“It contains major changes from previous models, because Gaia has changed our impression of the Milky Way. Even basic ideas have been revised, such as the rotation of our galaxy’s central bar, the warp of the disc, the detailed structure of spiral arms, and interstellar dust near the Sun,” says Stefan Payne-Wardenaar, scientific visualiser at the Max Planck Institute for Astronomy, Germany.
“Still, the distant parts of the Milky Way remain educated guesses based on incomplete data. With further Gaia data releases our view of the Milky Way will become even more accurate.”
Discovery machine of the decade
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. This is one of the favourite fields of researchers at the Strasbourg Astronomical Observatory, who have published several spectacular results on galactic archaeology.
In the process of scanning the stars in our own galaxy, Gaia has also spotted other objects, from asteroids in our Solar System backyard to galaxies and quasars – the bright and active centres of galaxies powered by supermassive black holes – outside our Milky Way.
More ground-breaking science ahead
The Gaia scientific and engineering teams are already working full steam on the preparations for Gaia Data Release 4 (DR4), expected in 2026. The data volume and quality improves with every release and Gaia DR4, with an expected 500 TB of data products, is no exception. Furthermore, it will cover the mission’s first 5.5 years, corresponding to the length of the originally foreseen duration of the mission.
“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,” says 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.”
Gaia DR4 is set to expand its binary star catalogue, the largest such catalogue to date. Gaia has a unique ability to tease out the tiny motions of pairs of celestial objects orbiting close to each other, and has already spotted previously hidden companions around bright stars.
The huge consortium of data processing specialists will also be stepping up preparations for the fifth and final major data release (Gaia DR5) at the end of this decade, which will cover all 10.5 years of data from the mission.
The CDS team is also getting ready to distribute these forthcoming catalogues, which will become essential references for a generation of astronomers.
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.
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--- Image sources :
- Gaia’s Milky Way: ESA/Gaia/DPAC, Stefan Payne-Wardenaar - CC BY-SA 3.0 IGO