On July 31, 2026, the NSF–DOE Vera C. Rubin Observatory released Early Data Preview 2 (EDP2) — the first science-grade data product built from observations made with the actual LSST Camera, the world's largest digital camera — alongside a stunning deep image of the COSMOS field packed with more than 500,000 galaxies and 50,000 stars. The release is a qualitatively different milestone from the telescope's June 2025 First Look event, which showcased images from a smaller prototype instrument. EDP2 is the first time the full 3.2-gigapixel LSST Camera science pipeline data — processed, calibrated, and catalogued — has been placed in researchers' hands.

The 500,000-galaxy COSMOS image, built by stacking hundreds of individual LSST Camera observations taken between April 2025 and January 2026, covers approximately 3,000 square degrees of the southern sky — roughly one-sixth of the Southern Hemisphere sky, captured in a single stacked frame. For comparison, the full Moon covers roughly one-fifth of one square degree; the COSMOS image spans the equivalent of 15,000 full Moons laid side by side.

Located in the constellation Sextans, the COSMOS field has been one of the most intensively studied patches of sky on Earth for more than two decades. Beginning with Hubble Space Telescope observations in 2003, researchers have directed the world's leading telescopes toward the same area, gathering data in wavelengths ranging from radio waves to X-rays. The field sits away from the dust-laden plane of the Milky Way, giving telescopes an unusually clean sightline into billions of light-years of cosmic structure.

COSMOS Field: Where Two Decades of Astronomy Converge

The cumulative result is a multi-wavelength reference library that no other sky patch can match. When Rubin images the COSMOS field, every galaxy it detects can be cross-referenced against decades of prior photometric, spectroscopic, radio, and X-ray measurements. That cross-referencing upgrades the value of every LSST detection — a galaxy that Rubin catches brightening or changing shape can be immediately placed in the context of everything prior observatories recorded about it.

What Rubin adds that prior instruments could not is repeated monitoring over time. Every previous COSMOS survey captured essentially a snapshot — light from these galaxies at a single moment in observing history. EDP2 is the first step toward transforming COSMOS from a static multi-wavelength atlas into an animated one: each return visit by the LSST Camera records how individual galaxies have changed, adding the dimension of time to a field that was previously known only as a series of fixed portraits. Over the course of the full decade-long Legacy Survey of Space and Time, astronomers expect hundreds of visits to this field.

"The COSMOS field is a very important one for LSST science," said Phil Marshall, Deputy Director of Rubin Observatory at SLAC. "Its wealth of prior observations, and its repeated targeting both during commissioning and as one of the LSST's deep fields, will make it very valuable as a testing ground for scientists as they get ready to take on the survey data."

What the LSST Camera Actually Does — and Why EDP2 Is Different

The LSST Camera is unlike anything previously deployed in astronomy. Its focal plane is a mosaic of 189 individual silicon charge-coupled device (CCD) sensors, each cooled to approximately -100°C (-148°F; 173 K) to suppress thermal noise. The sensors are deep-depletion, back-illuminated devices — a design in which light enters the silicon from the back rather than the front, maximizing the active pixel area and extending sensitivity across the full optical and near-infrared wavelength range. The entire 3.2-gigapixel focal plane reads out in just two seconds per image, enabling a cadence of one fully processed exposure every 40 seconds.

This speed matters because it determines how much sky the telescope covers per night. Each single exposure spans 9.6 square degrees of sky — approximately 45 full moons at once, the widest field of view ever achieved at this aperture class. The optical design that makes this possible is a three-mirror anastigmat: three non-spherical mirrors arranged to cancel spherical aberration, coma, and astigmatism simultaneously — the complete set of optical distortions that normally force wide-field telescopes to choose between resolution and sky coverage. No prior survey telescope of comparable aperture has achieved Rubin's combined field of view and resolution.

The June 2025 First Look images — which generated global attention — used the Commissioning Camera (ComCam), a smaller prototype instrument installed to calibrate the telescope before the full camera arrived. The LSST Camera itself was installed in March 2025 and began science validation observations in April 2025. EDP2 is the first release built from those LSST Camera observations, processed through the full Rubin Science Pipelines v30 software stack to produce calibrated, science-ready catalogs rather than raw demonstration images.

The distinction is substantial. The First Look event demonstrated what the instrument could see. EDP2 delivers what the instrument can measure — photometric magnitudes, positions, shapes, colors, and time-series information for every source in the catalog, ready for scientific analysis.

How 500,000 Galaxies Fit in a Single Frame

The number of galaxies in the EDP2 COSMOS image — more than 500,000 — did not arrive in a single exposure. They emerged from a process called image stacking, or coaddition: hundreds of individual 30-second exposures of the same sky region, taken on different nights across a nine-month science validation campaign, were aligned, calibrated, and combined.

Stacking deepens effective sensitivity. Random noise in any single image averages toward zero when many images are combined, while the faint but consistent light from a distant galaxy accumulates. The deeper the stack, the fainter the objects that become detectable — which is why the COSMOS image contains not just bright, nearby spirals and ellipticals but also faint red galaxies from the universe's distant past. Those reddened smudges represent light that has traveled billions of years before reaching Rubin's sensors — the telescope is seeing those galaxies as they existed in the universe's distant past.

What fills the frame between the 500,000 catalogued galaxies and the 50,000 foreground Milky Way stars is, in the words of the official release, an unusually clear view of galaxies stretching far into the distance. Because the COSMOS field points away from the Milky Way's galactic plane, fewer foreground stars and dust clouds block the sightline to extragalactic space than in most other directions.

What Comes Next: Difference Images and Transient Science

EDP2's current release includes deep coadded images and the full suite of measurement catalogs. The second phase of DP2, expected between October and December 2026, will add the data products that drive Rubin's transient science mission: processed visit images from individual observations, difference images showing only detected changes between exposures, and the template images used to produce those differences.

Difference images are the engine of the LSST's real-time alert pipeline. Every night, Rubin's automated software subtracts a reference template from the freshly acquired image, pixel by pixel. Any change — a new point of light, a brightness variation, a moving object — triggers an alert transmitted to a global network of astronomical broker systems within 60 seconds. With difference images available for the COSMOS field, researchers will be able to retrospectively study how sources in this well-characterized patch of sky have varied over the nine months of science validation observations — a preview of the decade-long light-curve archive the full LSST will eventually produce.

Bob Blum, Director of Rubin Observatory at NSF NOIRLab, framed the COSMOS work as a foundation for what follows: "Repeated visits to the field over the next few years will demonstrate the power of survey design for discovery by providing our science community with a huge number of transient and variable objects like supernovae and other explosive transients for follow-up and detailed study."

Access, Data Rights, and a Tribute to Coquimbo

Access to EDP2 is currently available to researchers in the United States and Chile, and to authorized international Rubin data-rights holders — including named members of 43 international in-kind teams that contribute to Rubin's program in exchange for access. The full public release is scheduled after a two-year proprietary period, expected around 2028.

Anyone can explore the COSMOS image in full resolution now via the Rubin Skyviewer app at skyviewer.app — an interactive, pannable interface that lets visitors navigate the 3,000-square-degree frame.

Blum added a note that framed the release against events closer to home: "As we celebrate the start of science with Rubin Observatory, our thoughts are with our staff and the community of Chile impacted by the recent devastating storms in the region of Coquimbo and beyond. Our priority is to ensure the well-being of our staff in the region and support the community where we live and work. This image marking the start of LSST science is dedicated to the people of the region of Coquimbo and is a small token of our gratitude for their decades of support for astronomy and the AURA Observatories in Chile."

Rubin Observatory stands on Cerro Pachón, which rises 2,682 meters (8,799 feet) above Coquimbo's Elqui Province — a site whose exceptional atmospheric stability, dark skies, and dry air the observatory has depended on since construction began a decade ago.

How Does Rubin's Galaxy Catalog Compare to Prior Surveys?

The EDP2 COSMOS catalog's 500,000+ galaxies, derived from nine months of commissioning observations across one-sixth of the southern sky, gives a preview of scale. The completed Legacy Survey of Space and Time will ultimately catalog approximately 20 billion galaxies and 17 billion stars. For comparison, the Sloan Digital Sky Survey — the most comprehensive sky survey completed before Rubin — catalogued approximately 500 million objects over its primary 14,555-square-degree coverage area at shallower photometric depth. Rubin's full-survey catalog, when complete, is expected to contain more data on individual astronomical objects than all prior optical surveys combined.

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Frequently Asked Questions

What is EDP2, and how is it different from Rubin's June 2025 First Look images?

EDP2 — Early Data Preview 2 — is Rubin Observatory's first science-grade data release based on observations from the LSST Camera, the full 3.2-gigapixel instrument. The June 2025 First Look images used the Commissioning Camera (ComCam), a smaller prototype installed for telescope alignment and testing. EDP2 is processed through Rubin's full science pipelines (v30) and delivers calibrated measurement catalogs — photometric magnitudes, positions, shapes, colors — ready for scientific analysis. The First Look demonstrated what Rubin could see; EDP2 delivers what Rubin can measure. Learn more at the official EDP2 documentation.

Why was the COSMOS field chosen for this image, and what makes it scientifically valuable?

The COSMOS field has been continuously observed since 2003 across virtually every astronomical wavelength — radio, optical, ultraviolet, X-ray, and infrared — by facilities including the Hubble Space Telescope, the Very Large Array, XMM-Newton, the Subaru Telescope, and the James Webb Space Telescope. That 20-year multi-wavelength archive means every Rubin detection can be cross-referenced against prior known properties of the same object. Rubin adds the one dimension that all prior COSMOS surveys lacked: repeated monitoring over time. EDP2 begins the transformation of COSMOS from a static atlas into an animated record of how hundreds of thousands of galaxies change over cosmic time.

When will the general public have access to Rubin's full science data?

EDP2 is currently restricted to researchers in the US and Chile plus authorized international in-kind program members. The full public release follows after a two-year proprietary period — expected around 2028 for EDP2-era data. The first full annual data release (DR1), built from the complete first year of the LSST survey, is expected approximately two years after the survey's June 30, 2026 start, also around 2028. The full completed LSST dataset — projected at roughly 500 petabytes — will be publicly accessible when the survey concludes in the mid-2030s. In the meantime, anyone can explore the COSMOS image right now at no cost using the Rubin Skyviewer at skyviewer.app.

What engineering capability lets Rubin image 45 full moons' worth of sky in a single 30-second exposure?

Three engineering choices combine to produce that field of view. First, the three-mirror anastigmat optical design — three precisely shaped non-spherical mirrors that together eliminate all three major categories of optical distortion — allows sharp focus across a 3.5-degree diameter field of view that a conventional two-mirror telescope of comparable aperture could not maintain. Second, the LSST Camera's 64-centimeter (25.2-inch) flat focal plane, tiled with 189 CCD sensors, physically covers that entire field simultaneously. Third, the two-second full-focal-plane readout speed — enabled by deep-depletion, back-illuminated CCDs cooled to -100°C (-148°F) — means the camera can complete a 30-second exposure and be ready for the next pointing within 40 seconds total. No prior wide-field camera combined all three capabilities at this scale.