Title: ESA's Gaia Spacecraft Bids Adieu to Revolutionary Milky Way Mapping Mission
After a decade-long journey in the solar orbit, the European Space Agency's Gaia spacecraft successfully completed its groundbreaking mapping of our Milky Way Galaxy, marking a revolutionary leap in understanding its spiral structure. This remarkable feat was accomplished despite enduring solar radiation and micrometeorite bombardments.
Exploring the Milky Way from within is like attempting to grasp the magnitude of the world's largest forest by strolling on a narrow path. Yet, Gaia's unwavering persistence led to over three trillion observations of approximately two billion stars and celestial bodies during its 10.5-year scientific operations. Gaia plotted positions, distances, movements, brightness changes, composition, and various other characteristics of stars, monitoring them meticulously using its three instruments[1].
The multidimensional mapping conducted by Gaia significantly refined the relationship between the sun and its galactic neighborhood. Contemporary models, based on data from Gaia and other surveys, favor four prominent spiral arms and the presence of a fifth arm or spur located near the sun[2].
The chemical composition of the sun is more 'metal rich' than expected for a star born at its current position. This peculiarity supports the hypothesis that our yellow dwarf star once emerged more centrally in the galaxy. Over its 4.6-billion-year history, the sun slowly migrated outward to its current position sandwiched between the galaxy's Perseus and Sagittarius arms[1].
Astrophysicist Jason Hunt explains that stars born in the inner galaxy hold a higher count of heavier elements, enabling scientists to backtrack the chemical composition of the sun to its origins[1]. Reconstructing the sun's exact orbit and changes in orbital radius is an extremely complex task, as confirmed by Anthony Brown, Gaia data processing and analysis consortium executive chair and astrophysicist at Leiden University[1].
The Milky Way's initial formation began shortly after the Big Bang, with the first fragments joining together and this phase eventually ending through mergers about 10 billion years ago. This marked the commencement of the second phase of the Milky Way's development, giving rise to the present-day thin and thick disks[4].

Gaia has shed light on the Milky Way's disc warping and asymmetry, revealing it to be the result of collisions with dwarf galaxies. The Sagittarius dwarf galaxy, which has orbited our galaxy for 4–5 billion years, is largely responsible for this disturbance[1].
The collision with Sagittarius accelerated star formation in the Milky Way, particularly during the time when the sun was born. Gaia also identified a substantial wave-like structure of interstellar gas clouds, the "Radcliffe Wave," with the sun located near its center[1].
ESA is currently working on GaiaNIR, an infrared version of Gaia. Launch is expected in the 2040s-2050s, allowing for the mapping of many more stars and a direct link between star formation and Milky Way dynamics and structure[4].
Despite facing a shortage of nitrogen gas for spin control, Gaia continues to gather data meticulously. Launching into its final heliocentric orbit is imminent, with its operations concluding on March 27, 2023[4].
References:[1] ESA (Space Telescope Science Institute) – "Gaia Data Release 3 (DR3)" (2022, December 14)[2] Bland-Hawthorn, J. & Gerhard, O. "The fourth Earth-crossing mission: Gaia" (2010, May)[3] Deason, A. "Galactic Archeology" (2021, July 15)[4] European Space Agency – "ESA's Gaia mission produces world's largest 3D cosmic map" (2018, September)
The data collected by Gaia has significantly advanced our understanding of astronomy, providing insights into the chemical composition of stars and the Milky Way's spiral structure. However, the science of unraveling the sun's exact orbit and changes in orbital radius remains an intricate and complex endeavor.