A new image captured by the Euclid space telescope provides the most detailed look yet at the heart of the Milky Way. This mosaic contains more than 60 million individual stars, alongside various nebulae and star clusters. The imagery will empower researchers to confirm the existence of exoplanets using the microlensing technique and calculate their masses with significantly improved accuracy.
Capabilities and Methodology
Although Euclid was primarily engineered to observe billions of distant galaxies, its visible-light camera possesses sufficient sensitivity to resolve individual stars within the Milky Way's core—an area that is both densely populated and exceptionally bright—without being obscured by the intense light. On March 23, 2025, Euclid directed its focus toward the galactic bulge, creating this massive image during just 26 hours of observation. The resulting mosaic is composed of nine distinct pointings, with each exposure covering an area of the sky larger than the full moon.
Comparing Observational Power
The quality of Euclid's visible-light images is comparable to that of the Hubble Space Telescope, yet there is a significant difference in speed and scale. Each pointing that Euclid achieves in a matter of hours covers a field of view 270 times larger than that of Hubble. To appreciate its efficiency, one should consider that the Keck Observatory would require approximately 2,000 hours to capture a comparable mosaic.
Exoplanets and Microlensing
This new image documents one of the most crowded regions of the Milky Way, making it a prime location for searching for exoplanets via gravitational microlensing. Jean-Philippe Beaulieu, who led the observing campaign, noted in a press release that to detect microlensing, one must observe areas of the sky densely packed with stars, such as the center of our galaxy. During the past two decades, nearly 300 exoplanets have been identified using this technique, all through ground-based telescopes pointed toward the galactic center. Euclid’s image includes 51 known planetary systems and will facilitate the study of many more yet to be discovered.
An Archive for Future Missions
While identifying a new microlensing event requires several weeks of observation, meaning Euclid could not record new events during its relatively short campaign, the value of the image lies in its data. It provides the essential metrics to measure the masses of known planets and those yet to be found. Natalia Rektsini, who led the data publication, explained that in just 24 hours, Euclid captured the stars involved in all future microlensing events that the Roman space telescope will detect, well before the stars and planets align. This allows researchers to use Euclid data as a historical reference, showing how stars appeared before they overlapped.
Broad Scientific Utility
Effectively, Euclid’s observations will function as a reference archive for upcoming missions, enabling more detailed exoplanet studies and precise mass measurements. Valeria Pettorino, ESA’s Euclid project scientist, highlighted that within 24 hours, the mission delivered unique, sharp, and wide-ranging data on the Milky Way’s center. These findings have potential for various scientific applications, ranging from studying brown dwarfs and binary stars to mapping stellar motions and dust distribution across our galaxy.
