Euclid captures 60 million stars in sharpest broad view of Milky Way's core

For just one day, our dark universe detective, Euclid, turned its gaze toward the light: the extremely bright inner region of our Milky Way galaxy, known as the galactic bulge. This special request came from astronomers who ...
Designed to observe billions of faraway galaxies, the space telescope's visible-light camera is sensitive enough to tell apart individual stars in our supercrowded galactic bulge without being blinded. This rare ability is crucial for what scientists want to use this image for: studying planets around other stars using a special technique called microlensing. But before diving into that, let's first take a closer look at this awe-inspiring image itself.

For comparison, Euclid's sharpness and sensitivity in visible light are similar to the NASA/ESA Hubble Space Telescope's wide-field camera. But each pointing that Euclid captures in a few hours spans an area 270 times larger than Hubble's field of view. To observe the same Euclid mosaic, the Keck Observatory would need around 2,000 hours. Euclid is faster and able to capture details from fainter stars that would otherwise be missed when observing from the ground. This single mosaic also encompasses the entire region that the upcoming Roman Space Telescope will monitor for planet hunting.
Euclid captured more than 60 million stars in this photo, along with nebulae and star clusters. This crowded region of our galaxy is the perfect place for astronomers to search for exoplanets with microlensing.

Finding exoplanets with gravitational microlensing

Microlensing is a form of gravitational lensing. While Euclid mostly uses lensing to explore massive faraway objects, such as clusters of galaxies, this new image of the galactic center helps scientists study lenses on the smallest scales—caused by stars and exoplanets in our own galaxy.

Microlensing relies on the chance alignment of two stars with an observer. As one star crosses in front of another, the nearer star acts like a cosmic magnifying glass, bending and brightening the background star's light. If a planet orbits the nearer star, its gravity also bends this light, in a slightly uneven way. This tiny additional change in brightness is how the presence of a planet is revealed.

This is the largest high-resolution photo ever made of our Milky Way galaxy's centre in visible light. It was taken on 23 March 2025 by the European Space Agency's Euclid space telescope. Packed with more than 60 million stars, this image opens the door for scientists to confirm the existence of any exoplanet found in this region and measure its mass using tiny changes in starlight over time. The galactic bulge—the central region of our galaxy—is a vast, tightly packed structure filled mainly with old, cooler stars, giving it its characteristic yellow colour. Seen from some 26 000 light-years away, Euclid observes the galaxy's centre through a complex foreground of material along its line of sight. This ultra-wide view towards the bulge reveals not only stars, but also seemingly empty dark regions. The dark patches are not devoid of stars: they mark dense, dust-rich molecular clouds that absorb and scatter light from the bulge behind them. As Euclid looks through two of the Milky Way's spiral arms, it also encounters regions of active star formation, traced by newly formed, massive blue stars. Their intense ultraviolet radiation ionises surrounding hydrogen gas, producing the faint red glow clearly visible in one of the cutouts. Credit: ESA/Euclid/Euclid Consortium/NASA, CFHT, image processing by J.-C. Cuillandre and E. Bertin (CEA Paris-Saclay)
Read more

Two zooms show the staggering resolution of Euclid's image. The most zoomed-in vignette on the lower right corresponds to 0.003% of the galactic bulge survey area (which is 4.8 square degrees in total). With many thousands of stars discernible in this tiny area, the entire Euclid galactic bulge image charts no less than 60 million stars. Credit: ESA/Euclid/Euclid Consortium/NASA, CFHT, ESA/Gaia/DPAC,image processing by J.-C. Cuillandre and E. Bertin (CEA Paris-Saclay)
Read more

This infographic places Euclid’s galactic bulge survey in the broader context of the Milky Way’s structure, using data from ESA’s Gaia mission. The top row shows schematic views (artist impressions) of our spiral galaxy: an edge-on view highlighting the central bulge (top left), a top-down view revealing the spiral arms and the survey region (top centre), and a zoom into the galactic disc indicating the location of the Solar System (top right), from where Euclid observes the sky, which turns into the main background of the visual. The lower panel illustrates the diversity of objects captured by Euclid as it observed towards the galactic bulge in March 2025. Moving from left to right, the numbered cutouts highlight dense molecular clouds that obscure background starlight, a glowing emission nebula associated with recent star formation, a young star cluster, and finally the galactic bulge itself – a dense, spheroidal region containing ten billion stars. This crowded central region provides ideal conditions for detecting microlensing events. Credit: Euclid images: ESA/Euclid/Euclid Consortium/NASA, CFHT, image processing by J.-C. Cuillandre and E. Bertin (CEA Paris-Saclay); Milky Way artist impressions: ESA/Gaia/DPAC, Stefan Payne-Wardenaar)
Read more