The Vera Rubin Observatory is an astronomical facility on Cerro Pachón, 2,500 metres up in the foothills of the Andes in northern Chile. It is named after Vera Rubin, the American astronomer who provided evidence for the existence of dark matter in the 1970s. Construction began in 2015.
The observatory recorded its first photons of starlight on April 15th 2025. Its primary mission, the Legacy Survey of Space and Time (LSST), is a ten-year project scheduled to begin in October 2025. The LSST will repeatedly photograph the entire night sky of the southern hemisphere every three or four days, producing a decade-long time-lapse of the cosmos.
The observatory's camera is the biggest digital camera ever built: 1.7 metres long and 3,200 megapixels. Its field of view covers an area of sky equivalent to 45 full Moons. Light is gathered by a primary mirror 8.4 metres wide, which took scientists at the University of Arizona seven years to grind into shape. The telescope can take an image every 30 seconds, with a machine-learning scheduler automatically selecting where to point the camera each night.
In its first year alone, Rubin will double the amount of data collected by every other instrument in the history of optical astronomy. It will collect 20 terabytes of raw image data per night and, over the full LSST, produce more than 500 petabytes of images and analysis. Each point in the sky will be photographed around 800 times over the decade.
Data are transferred within ten seconds of capture, through dedicated optical fibres, to the SLAC National Accelerator Laboratory in California, with backups sent to data centres in France and Britain. Automated algorithms winnow millions of nightly alerts—new objects, changes in position or brightness—into a priority list passed on to other observatories worldwide.
The LSST is expected to catalogue more than 17bn stars and 20bn galaxies, and discover more than 40bn new cosmic objects in total. It will conduct the most detailed census yet of unknown objects in the solar system, tripling the number of known objects that could approach Earth and finding around 70% of asteroids classed as "potentially hazardous" (those bigger than 140 metres wide). In an early test, ten hours of observations identified more than 2,000 previously unknown asteroids, including seven near-Earth asteroids—compared with around 20,000 discovered annually by all other observatories combined.
The LSST could also spot dozens of interstellar objects—comets and asteroids formed around distant stars and ejected into the Milky Way—over the next ten years. 3I/ATLAS, an interstellar comet discovered on July 1st 2025 by the ATLAS project in Chile, was only the third such object ever detected (after 1I/'Oumuamua in 2017). A preprint by researchers at the University of Oxford concluded that 3I/ATLAS is probably more than 7bn years old and originated among the Milky Way's "thick disc" of old stars. Astronomers estimate there may be around 10^26 interstellar objects in the galaxy, a million billion times more than the number of stars. Building a proper population catalogue of these objects would be "transformative", according to Chris Lintott, an astronomer at Oxford.
The observatory may also help resolve the Hubble tension, the persistent discrepancy between two ways of measuring how fast the universe is expanding.
Two of the observatory's prime goals are understanding the nature of dark matter and dark energy. Dark energy makes up roughly 68% of the mass in the universe and dark matter around 27%; only about 5% comes from normal matter. Rubin will measure how light from very distant galaxies is distorted by intervening matter (gravitational lensing), revealing how matter is distributed and moving. It is also expected to discover billions of supernovae, vastly expanding the data set used to study dark energy. The phenomenon was originally discovered in the 1990s through observations of a few dozen supernovae.
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