MILKY WAY — The European Space Agency released an image of the Milky Way's galactic bulge captured by the Euclid space telescope on March 23, 2025. The image captures more than 60 million stars and includes 51 known planetary systems.

The observation took approximately 26 cumulative hours. The image is a mosaic of nine pointings from Euclid's visible light camera, with each pointing covering a patch of sky larger than the full Moon. Euclid's visible light camera has sharpness and sensitivity in visible light similar to the Hubble Space Telescope's wide field camera, but each Euclid pointing spans an area 270 times larger than Hubble's field of view.

The Euclid image data will serve as a time reference for future microlensing events detected by other telescopes. No new microlensing events were discovered during Euclid's one-day observation of the galactic bulge. Detecting a microlensing event requires observing a star for over 20 days.

"In 24 hours, Euclid has already captured the stars involved in all the future microlensing events that the Roman space telescope will detect, but before the stars and planets involved have aligned," said astronomer Natalia Rektsini. "This means that anyone who detects a microlensing event in the same region, for example with Roman, will be able from now on to use Euclid data as a time reference in the past and see how the stars looked before they overlapped." Rektsini added, "Since Euclid can clearly separate individual stars, one can then measure how fast they move over time and use that information to confirm the existence of a planet and determine its mass." She noted, "This would not be possible with data from one point in time."

"To catch microlensing, you need to observe parts of the sky that are crowded with stars, such as close to the centre of our galaxy," said astronomer Jean-Philippe Beaulieu. "During the last twenty years, almost 300 exoplanets have been discovered using this technique, all with ground-based telescopes and all towards the centre of our galaxy." Beaulieu stated, "This image from Euclid includes 51 known planetary systems – and it will assist in studying many more that will be found." Euclid was launched in July 2023 and started routine science observations on February 14, 2024.

The original Euclid image is in black and white because only the visible camera was used for stability. Color was added to the public release image using data from the Canada-France-Hawai'i Telescope. The image also includes nebulas and star clusters. Observing the same area covered by the Euclid mosaic would require approximately 2000 hours with the Keck Observatory.