Vera C. Rubin Observatory Surveys of the Observable Universe

​The Vera C. Rubin Observatory’s Legacy of Space and Time (LSST) is a groundbreaking astronomical facility on Cerro Pachón in Chile, equipped with an 8.4-meter Simonyi Survey Telescope and the world’s largest digital camera (3.2 gigapixels). It conducts the 10-year Legacy Survey of Space and Time (LSST), repeatedly imaging the entire visible southern sky every few nights to create vast datasets, around 500 petabytes total, for transformative science. The key science areas it focuses on are:
Dark Matter & Energy: Probes these mysterious components by mapping billions of galaxies, measuring weak lensing, supernovae, and cosmic expansion.
 
Solar System Inventory: Detects millions of asteroids (including 60-90% of hazardous ones >140m), comets, and Kuiper Belt objects to track planetary formation and risks.
 
Milky Way Mapping: Charts our galaxy’s structure, history, and mergers through hundreds of observations per sky patch.
 
Transient Sky: Alerts on rapid changes like supernovae, novae, and gravitational wave counterparts within minutes.
 
The LSST does not map universes, it surveys the observable Universe by imaging the southern sky to catalog tens of billions of objects, including about 20 billion galaxies. LSST will detect roughly 38 billion total objects over 10 years: 20 billion galaxies, 17 billion stars, 10 million supernovae, and 6 million Solar System bodies.
Early test images already captured 10 million galaxies in a single 3.2-gigapixel frame (0.05% of the planned total), many previously unseen, zooming out from Virgo Cluster galaxies.
This wide-field survey (10 square degrees per image, ~100 visits per sky patch yearly) enables precise mapping of galaxy distributions to study dark matter, cosmic structure, and expansion.
 
Current estimates suggest there are approximately 2 trillion galaxies in the observable universe. This number is based on analyses of deep-space images, such as those from the Hubble Space Telescope, which indicate that earlier, lower estimates of 100–200 billion galaxies missed a vast number of smaller, fainter, and distant galaxies. The "2 trillion" figure applies only to the observable universe, which is the part we can potentially see. The entire universe may be infinite or much larger.
 
References
(2026). About Rubin Observatory. Vera C. Rubin Observatory. https://www.lsst.org/about
 
(2026, March3). Vera C. Rubin Observatory. In Wikipedia, https://en.wikipedia.org/wiki/Vera_C._Rubin_Observatory