On a single day in March 2025, a space telescope named Euclid captured more stars in one image than most astronomers will catalogue in a lifetime. The European Space Agency's observatory turned its gaze toward the galactic bulge—the dense, golden heart of the Milky Way—and in just a few hours produced the largest high-resolution photograph ever made of this region in visible light. Packed into that single mosaic are more than 60 million stars, along with glowing nebulae and dark patches that are not empty at all, but dense clouds of dust swallowing light from the stars behind them. The image was released publicly and offers scientists an unprecedented new tool for hunting planets beyond our solar system.
The galactic bulge sits roughly 26,000 light-years from Earth. It is a vast, tightly packed region dominated by older, cooler stars that give it a distinctive yellowish hue. Observing it is extraordinarily difficult because material along Euclid's line of sight scatters and blocks starlight. Yet Euclid's visible-light camera proved sensitive enough to distinguish individual stars in this supercrowded neighborhood without being overwhelmed by the glare. For comparison, each observation Euclid captures spans an area 270 times larger than the Hubble Space Telescope's wide-field camera can capture in the same time. To image the same region using the Keck Observatory in Hawaii would require roughly 2,000 hours of telescope time.
The image was no accident. Jean-Philippe Beaulieu of the Institut d'Astrophysique de Paris and the University of Tasmania proposed the observation. A co-leader of the Euclid Consortium's exoplanet working group, Beaulieu had spent years pushing for a dedicated survey of the galactic bulge—and for a clear reason. This crowded region of space is exactly where the technique called gravitational microlensing works best. Microlensing relies on a rare cosmic coincidence: when one star passes in front of another, its gravity acts as a magnifying glass, bending and brightening the background star's light. If a planet orbits the nearer star, its smaller gravitational pull creates a tiny, detectable irregularity in that brightening. Over the past two decades, ground-based telescopes have found nearly 300 exoplanets using this method, all pointing toward the galactic center. Euclid's new image already captures 51 known planetary systems in this region, and scientists say it will sharpen their ability to measure the masses of exoplanets already discovered—and find ones that ground telescopes alone could never catch.
The Euclid mission was originally designed to study billions of distant galaxies, but this image demonstrates its unexpected power closer to home. The mosaic covers 4.8 square degrees of sky, precisely the same region that NASA's upcoming Roman Space Telescope will monitor for planet hunting. With this single photograph, Euclid has handed astronomers a map of extraordinary depth and clarity, and the search for new worlds has only just begun.