Full Breakdown
Euclid Delivers Record-Breaking Visible-Light Portrait of the Milky Way’s Crowded Heart
6/25/2026, 4:03:24 AM
Record-Breaking Galactic Bulge Mosaic
On a single-day campaign, the European Space Agency’s Euclid telescope produced the most detailed visible-light image ever of the Milky Way’s central bulge. The mosaic, assembled from nine adjacent pointings each larger than the full Moon, contains more than 60 million resolved stars, nebulae and star clusters. The observations spanned 26 hours, yielding an 18 000 × 18 000-pixel (324-megapixel) picture that covers an area 270 times larger than a single Hubble Wide-Field Camera field.
Mission Background and Rationale
Euclid was launched in 2023 to map billions of distant galaxies and probe dark energy and dark matter. Its visible-light camera, designed for faint, distant sources, is also capable of separating individual stars in extremely dense fields. Astronomers therefore requested a brief “galactic bulge survey” to obtain a high-resolution reference for gravitational-microlensing studies of exoplanets—an application far from Euclid’s primary cosmological goals.
Principal Scientists and Collaborators
- Jean-Philippe Beaulieu (Institut d’Astrophysique de Paris / University of Tasmania) – initiator of the bulge survey and co-lead of Euclid’s exoplanet working group.
- Jean-Charles Cuillandre (ESA Euclid mission scientist) – provided technical oversight of the observation.
- Valeria Pettorino (ESA Euclid project scientist) – commented on the data’s uniqueness.
- Natalia Rektsini (postdoctoral fellow, Institut d’Astrophysique de Paris) – led the public data release.
- Andrew Kerins (Euclid scientist) – evaluated measurement improvements.
- NASA’s Roman Space Telescope team – will use the Euclid mosaic as a baseline for its own microlensing survey.
Data Highlights
- Stars captured: > 60 million; known planetary systems: 51.
- Microlensing legacy: ? 300 exoplanets discovered by this technique over the past two decades.
- Field size: each pointing > full Moon; total area 270 × Hubble’s field of view.
- Efficiency: Keck Observatory would require ~2 000 hours to match Euclid’s coverage.
- Observation date: reported as 23 March 2025 in several sources, but a subset cites 23 March 2026, indicating a reporting discrepancy.
Scientific Significance
Microlensing relies on a foreground star acting as a gravitational lens for a background star; a planet orbiting the lens star produces a subtle asymmetry in the brightening curve. Euclid’s ability to resolve individual stars in the bulge supplies a precise “pre-event” reference, allowing future missions to measure stellar motions and planetary masses with up to three-fold improved accuracy. The mosaic therefore underpins the upcoming Roman telescope’s planet-hunting campaign and enables retrospective mass determinations for planets already identified.
Official Statements
ESA emphasized that Euclid’s visible-light camera “is sensitive enough to tell apart individual stars in our super-crowded galactic bulge, without being blinded.” NASA’s Roman team confirmed that the Euclid dataset “encompasses the entire region that Roman will monitor for microlensing events,” positioning it as a critical time-reference archive.
Limitations and Open Issues
The 26-hour window was too brief to capture an active microlensing event, which typically requires > 20 days of continuous monitoring. The conflicting observation dates (2025 vs. 2026) remain unresolved in the public record.
Verbatim Quotes
- “Now we've decided to point Euclid at the brightest area of the sky -- and it works superbly, it's extraordinary,” — Jean-Charles Cuillandre, ESA Euclid mission scientist.
- “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,” — Jean-Philippe Beaulieu, Institut d’Astrophysique de Paris.
- “During the last twenty years, almost 300 exoplanets have been discovered using this technique, all with ground-based telescopes and all towards the center of our galaxy. This image from Euclid includes 51 known planetary systems — and it will assist in studying many more that will be found,” — Jean-Philippe Beaulieu.
- “In just 24 hours, Euclid has delivered unique data on the Milky Way’s centre, with a large and sharp view of this region,” — Valeria Pettorino, ESA project scientist.
- “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,” — Natalia Rektsini, Institut d’Astrophysique de Paris.
- “The Euclid snapshot will improve those measurements possibly by up to a factor of three, which for a single image is quite something,” — Andrew Kerins, Euclid scientist.
Future Outlook
The Roman Space Telescope is slated for launch in August (year unspecified) and will conduct a dedicated microlensing survey of the same bulge region. Euclid’s full-resolution dataset will be released to the broader community later this year, enabling ongoing refinement of stellar motion catalogs and mass estimates for both known and newly discovered exoplanets.
