Euclid Galactic Bulge Survey Reveals 60 Million Milky Way Stars

The Euclid Galactic Bulge Survey has delivered its first public trove of data, and the numbers are hard to ignore: more than 60 million stars, packed into a single high-resolution mosaic of the Milky Way’s crowded core. On 24 June 2026, the Euclid Consortium and the European Space Agency released Quick Data Release 2 (Q2), built from a dedicated observing campaign the Euclid space telescope carried out near the Galactic Centre back in March 2025. It is a different kind of Euclid product than most people expect from a dark-energy mission, and it arrives just weeks after Euclid grabbed headlines for spotting some of the most distant quasars ever recorded. The bulge survey is a separate release, built for a very different scientific purpose: finding and measuring planets around other stars.

What the Euclid Galactic Bulge Survey Actually Observed

According to the Euclid Consortium’s press release, the telescope turned toward a region near the Galactic Centre on 23 March 2025 and spent approximately 26 hours capturing nine contiguous fields covering 4.8 square degrees of sky. The observations relied solely on Euclid’s VIS instrument, a 600-megapixel visible-light camera, which recorded more than 60 million stars at a resolution of about 0.16 arcseconds. Each of the nine fields received 16 dithered exposures of 400 seconds, for roughly 1.8 hours of total exposure per field. The result is an image the Consortium describes as an exceptionally deep, wide-field, high-resolution view of the Milky Way’s inner bulge, released alongside calibrated images and astrometry and photometry catalogues for every detected star in the field.

Why Scientists Pointed Euclid at the Galactic Centre

The Euclid Galactic Bulge Survey (EGBS) was not designed as a cosmology product. It is, first and foremost, an exoplanet-hunting campaign built around a technique called gravitational microlensing. When a foreground star, or a star with an orbiting planet, passes in front of a more distant background star from Earth’s point of view, its gravity briefly bends and magnifies the background star’s light. The result is a smooth, bell-shaped brightening that can last for weeks; if the foreground star hosts a planet, the planet adds a much shorter blip, lasting hours to days, on top of that curve. Astrophysicist Matthew Penny of Louisiana State University, who leads Euclid’s exoplanet team, notes that toward the Galactic Centre the odds of catching such an alignment are roughly one in a million, compared with about one in a billion along other lines of sight, which is exactly why the bulge is the target of choice for this kind of survey.

Because the EGBS field overlaps with regions where ground-based telescopes have already recorded microlensing events over the past two decades, Euclid’s new images give researchers a second, much later snapshot of those same patches of sky. Astrophysicist Eamonn Kerins of the University of Manchester explains that this time gap lets scientists track how the lensing star has physically moved since the original event, which in turn sharpens mass estimates for the planets involved, in some cases down to the mass of Mars. Consortium scientists estimate the dataset will support refined mass measurements for roughly 60 exoplanets already catalogued within the survey footprint.

Beyond Exoplanets: What a Bulge Survey Like This Enables

The headline goal of EGBS is exoplanet characterisation, but a catalogue of 60 million precisely measured stellar positions and brightnesses in one of the densest parts of the galaxy has value that extends well beyond planet-hunting. It is worth being explicit here about what is documented fact versus reasonable inference: the Consortium’s own ‘behind the scenes’ write-up on the release states that the EGBS data will also support dynamical studies of the Galactic disk at low latitude, searches for asteroids, and improved characterisation of rare stellar populations such as compact objects and planetary nebulae in the inner Milky Way. Beyond that explicit statement, it is a reasonable inference — not a claim made in the press materials — that any survey this deep and this precise toward the Galactic bulge will also feed broader questions about how the bulge’s stellar populations formed and how the Milky Way’s central structure evolved, since astrometry and photometry catalogues of this size are standard inputs for that kind of structural and population analysis. Readers should treat that broader framing as informed context rather than a specific finding announced in Q2.

EGBS and NASA’s Roman Telescope

Part of the strategic value of this bulge survey lies in its timing. NASA’s Nancy Grace Roman Space Telescope, scheduled to launch on 30 September 2026, will begin its own Galactic Bulge time-domain microlensing programme in 2027, observing the same general region repeatedly to catch planets in the act of lensing. Because Euclid has already imaged that field in detail, Consortium scientists say they can use the Q2 data to precisely identify the foreground lens systems ahead of time, so that when Roman detects new microlensing events, researchers already have a baseline against which to measure them. Astrophysicist Etienne Bachelet has said Roman is expected to discover at least 1,200 planets over its microlensing survey, including around 200 in 2027 alone, with Euclid providing the precise mass measurements needed to turn those detections into a real census of cold planets across the galaxy.

Limitations of the Q2 Data

• The EGBS release does not include a new tally of confirmed exoplanets; it provides imaging and catalogues meant to refine mass estimates for planets found by other surveys over the past 20 years.
• The observations used only Euclid’s visible-light VIS instrument, not its near-infrared spectrometer and photometer, so the release does not include infrared colour or spectroscopic data for the bulge stars.
• Euclid Consortium technical documentation notes the source catalogues remain affected by incompleteness and spatial inhomogeneities caused by extreme stellar crowding in this part of the sky, which is far denser than Euclid’s normal wide-survey fields.
• Broader claims about what the data implies for Milky Way structure and stellar population history are reasonable extrapolations from the survey’s scope, not specific results announced in the June 2026 release.

FAQ: Euclid Galactic Bulge Survey

What is the Euclid Galactic Bulge Survey?

It is a dedicated Euclid observing campaign, released as Quick Data Release 2 (Q2) on 24 June 2026, that imaged 4.8 square degrees near the Milky Way’s centre and catalogued more than 60 million stars to support exoplanet research through gravitational microlensing.

Is this the same as Euclid’s quasar discovery?

No. This bulge survey is a separate release from the 6 July 2026 announcement of 31 newly identified early-Universe quasars. Both are Euclid science products, but they use different observations for different purposes.

Why does the survey focus on exoplanets rather than dark energy?

Euclid’s main mission is mapping dark matter and dark energy, but the Consortium designed this auxiliary campaign specifically to exploit Euclid’s sharp imaging for gravitational microlensing, a technique that works best in extremely dense stellar fields like the Galactic bulge.

Bottom Line

The Euclid Galactic Bulge Survey shows that a mission built to chart dark energy can also deliver some of the sharpest exoplanet-hunting data available, by training its camera on 60 million stars in the Milky Way’s crowded centre. The real payoff will come as researchers combine this Q2 catalogue with ground-based microlensing archives and, later, NASA’s Roman telescope, turning a single deep image into precise mass measurements for dozens of known worlds and, eventually, a genuine census of cold planets across the galaxy.

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Featured image: Photo via Unsplash (photo-1419242902214-272b3f66ee7a); free to use under the Unsplash License. Illustrative only.