24/06/2026
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In brief
The largest and most detailed photo ever taken in visible light of the center of our Milky Way will be released on June 24, 2026, by the Euclid mission of the European Space Agency (ESA). Featuring more than 60 million stars, this image allows scientists to confirm the existence of exoplanets in this region and measure their mass based on tiny changes in starlight over time.
In-depth
For just one day, Euclid, our detective of the dark universe, turned its gaze to the light: the extremely bright inner region of our Milky Way, known as the galactic bulge. This special request came from astronomers who wanted precisely what Euclid does best: capturing vast areas of the sky in sharp detail.
Designed for observing billions of distant galaxies, the visible-light camera aboard the telescope is sensitive enough to differentiate individual stars in our crowded galactic bulge without being overwhelmed by their brightness. This rare capability is vital for what scientists intend to do with this image: to investigate planets around other stars using a technique called gravitational microlensing. Before diving into that, however, let’s take a closer look at this impressive image itself.
On March 23, 2025, Euclid captured this massive image in just about 26 hours. It consists of a mosaic from nine “pointings” of its visible-light camera, with each pointing covering an area of the sky larger than the full moon.
By comparison, Euclid’s sharpness and sensitivity in visible light are akin to NASA/ESA’s Hubble Space Telescope’s Wide Field Camera. Yet, each image that Euclid captures in a few hours spans an area 270 times larger than Hubble’s field of view. Observing the same Euclid mosaic would take the Keck Observatory roughly 2000 hours. Euclid is faster and capable of capturing details of fainter stars that would otherwise be overlooked in ground-based observations. This single mosaic also encompasses the entire region that the future Roman Space Telescope will monitor for planets.
Euclid captured more than 60 million stars along with nebulae and star clusters in this image. This densely populated region of our galaxy is the ideal location for astronomers to search for exoplanets using the microlensing effect.
The Search for Exoplanets via Gravitational Microlensing
The microlensing effect is a form of gravitational lensing. While Euclid primarily employs lensing effects to study massive, distant objects like galaxy clusters, this new image of the galactic center allows scientists to examine lenses on a smaller scale—caused by stars and exoplanets in our own galaxy.
The microlensing effect relies on the random alignment of two stars from the observer’s perspective. When one star passes in front of another, the closer star acts as a cosmic magnifying glass, bending and brightening the light of the background star. If a planet orbits the nearer star, its gravity also distorts that light—albeit in a slightly uneven manner. This tiny variation in brightness can confirm the presence of a planet.
“To discover microlenses, one must observe areas of the sky that contain many stars, such as near the center of our galaxy,” explains Jean-Philippe Beaulieu from the Institute d’Astrophysique de Paris, France, and the University of Tasmania, Australia. Jean-Philippe initiated the Euclid survey of the galactic bulge and co-led the exoplanet working group for the Euclid Consortium.
“In the past twenty years, nearly 300 exoplanets have been discovered using this technique, all with ground-based telescopes and all aimed toward the center of our galaxy. This image from Euclid encompasses 51 known planetary systems, and it’s set to help investigate many more that have yet to be discovered,” he adds.
Measuring Planet Masses with Euclid
To capture a microlensing event, a telescope must observe a star for over twenty days. This is essential to detect the irregularities in the light being bent as the planet orbits its host star. Hence, no new events can be discovered during a single observation day by Euclid. However, what makes this image special is that it enables scientists to measure the mass of already known planets, as well as those yet to be discovered.
“This means that anyone who discovers a microlensing event in the same region—such as with Roman—can now utilize the Euclid data as a temporal reference to see how the stars looked before they overlapped,” Natalia explains. “Since Euclid can clearly differentiate individual stars, it becomes possible to measure how fast they move over time and, based on this information, confirm a planet’s existence and determine its mass. This would not be feasible with data capturing only a specific point in time.”
Ice Planets and Beyond
In most planet-hunting methods, it’s easier to find large, hot planets orbiting massive stars. However, that’s not the case with microlensing. “This method is unbiased—we discover whatever is out there,” says Natalia. “It uniquely excels at discovering cold exoplanets. We postulate that every star in the Milky Way harbors at least one such planet.”
The parent stars of two well-known cold exoplanets appear in Euclid’s data, and both hold special significance for the team.
“I led the team that discovered OGLE-2005-BLG-390Lb twenty years ago,” Jean-Philippe relates. “It’s an icy planet, a little like Hoth from Star Wars. After all this time, I am excited that Euclid may finally allow us to determine its exact mass.”
“OGLE-2013-BLG-341Lb is a rare and fascinating system,” Natalia states. “It consists of two stars and a planet. By combining earlier observations from Keck and Hubble with new Euclid data, we can finally distinguish the stars from one another and confirm the planet’s mass.”
“This outcome illustrates what a relatively small, dedicated team can achieve within a large international mission,” says Valeria Pettorino, Euclid’s project scientist at ESA. “The exoplanet team benefited from valuable contributions from early-career researchers and was supported by the Science Ground Segment unit working on the visible instrument.”
“In just 24 hours, Euclid has delivered unique data about the center of the Milky Way, providing a broad and sharp view of this region. Over time, the distance between sources and lenses increases. Therefore, this Euclid data will serve as a temporal reference point for past and future missions, facilitating the study of exoplanets and their masses. This data can also be utilized for other scientific applications, ranging from brown dwarfs and binary stars to stellar motions and dust in our galaxy.”
Editor’s Notes
Explore this image in high resolution on ESASky starting June 24.
Find more information on downloading the new Euclid data here.
For the galactic bulge survey, only Euclid’s Visible (VIS) camera was used to keep observations as stable as possible. Consequently, the original image is in black and white. To colorize the photo for this release, data from the ground-based Canada-France-Hawai’i Telescope (CFHT) were added.
About Euclid
Euclid was launched in July 2023 and began routine scientific observations on February 14, 2024. The mission aims to uncover the hidden influence of dark matter and dark energy on the visible universe. Over a six-year period, Euclid will observe the shapes, distances, and motions of billions of galaxies up to a distance of 10 billion light-years.
Euclid is a European mission built and operated by ESA, with contributions from NASA. The Euclid Consortium—including over 2000 scientists from 300 institutions across 15 European countries, the USA, Canada, and Japan—provides scientific instruments and performs data analysis. ESA selected Thales Alenia Space as the prime contractor for the satellite and its service module, while Airbus Defence and Space developed the payload module, including the telescope. NASA supplied the detectors for the Near Infrared Spectrometer and Photometer (NISP). Euclid is a mid-class mission under ESA’s “Cosmic Vision” program.
