Rubin Observatory captures 500,000 galaxies, then helps spot rare supernova

The Vera C. Rubin Observatory has released a sweeping image of the COSMOS field containing more than half a million galaxies and over 50,000 stars, marking its first science-grade data release from the LSST Camera. Within days of the release, the observatory also proved its value as a real-time discovery machine, helping a global fleet of telescopes capture one of the rarest events in modern astronomy: the shock breakout of a dying star.

A Deep Window on the Cosmos

Released on July 31 to mark the observatory's Early Data Preview 2, the image was created by stacking hundreds of individual observations taken between April 2025 and January 2026. It features the COSMOS field in the constellation Sextans, one of the most studied patches of the sky, first targeted by the Hubble Space Telescope in 2003.rubinobservatory

Rubin's 3.2-gigapixel LSST Camera — the largest digital camera ever built for astronomy — is mounted on the 8.4-meter Simonyi Survey Telescope at Cerro Pachón in Chile. Its focal plane holds 189 science CCD sensors cooled to around -100°C, and each exposure captures 9.6 square degrees of sky, an area equivalent to roughly 45 full Moons. A wider view of the same region reveals more than 650,000 galaxies and over 75,000 stars.zmescience+2

"The COSMOS deep image is just the beginning for Rubin in this region," said Bob Blum, director of Rubin Observatory at NSF NOIRLab. "Repeated visits to the field over the next few years will demonstrate the power of our survey design for discovery."rubinobservatory

Catching a Star's Final Moments

Days after the COSMOS release, the observatory demonstrated exactly that kind of discovery power. In March, China's Einstein Probe space telescope detected a brief flash of X-rays from a source 500 million light-years away. Ground-based telescopes responded within the hour, and Rubin happened to be monitoring the same patch of sky. The event, designated SN 2026gzf, was classified as a Type Ic broad-lined supernova — the explosive death of a Wolf-Rayet star roughly 20 times the mass of the sun.livescience+1

Two teams published results on July 14 in The Astrophysical Journal Letters, each independently confirming the "shock breakout," only the second such observation in 20 years. The supernova's shock breakout was the faintest ever associated with an Ic-BL supernova, and no gamma-ray bursts were detected — a surprise, since this type of explosion is often linked to such bursts.petapixel+1

"One possibility is that the jet was 'choked,' either by the surface of the star or by circumstellar material surrounding the star," said Brendan O'Connor, an astrophysicist at Carnegie Mellon University and co-author of one of the studies.livescience

The Decade Ahead

Over its planned 10-year Legacy Survey of Space and Time, Rubin is expected to detect roughly 20 billion galaxies and 17 billion stars, issuing up to seven million alerts per night to flag supernovae, asteroids, and other transient events. EDP2 data is currently available to researchers in the United States and Chile, with public access planned after a two-year proprietary period. A second phase of the data release, adding difference images that reveal changes between observations, is expected later in 2026.thedailystar+2