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The new Vera C. Rubin Observatory detected interstellar object 3I/ATLAS and may detect up to 50 more during its 10-year mission, according to a new model.
The observatory in Chile, which unveiled its first images last month, is equipped with a unique view of the night sky, supported by the world's largest camera.
A new survey telescope in Chile, the Rubin Observatory, looks set to become astronomy's most ambitious and productive eye on the sky ever made. It will begin a 10-year mission later this year, during which it's expected to discover 10 million supernovas, 20 billion galaxies, and millions of asteroids and comets.
About the size of a car, Rubin's $168 million LSSTCam imager -- the most sensitive optical device ever made -- weighs over three tons and captures 3,200-megapixel images. Every image is big enough to fill 378 4K screens. It took 10 years to manufacture, features six optical filters, and, crucially, has a 9.6 square-degree field of view -- it can see a large portion of the sky at once.
Discovered on July 1, 2025, by the ATLAS telescope network at El Sauce Observatory in Chile and thought to be around 12 miles (20 kilometers) in diameter, 3I/ATLAS's eccentric trajectory suggests that it's from outside the solar system. The third interstellar object ever to be found after 'Oumuamua in 2017 and a comet called 2I/Borisov in 2019, 3I/ATLAS could be three billion years older than the solar system -- the oldest comet ever seen. It could even be up to 14 billion years old, according to Matthew Hopkins, an astronomer at the University of Oxford, who spoke on July 11 at the Royal Astronomical Society's National Astronomy Meeting in Durham, U.K., about a new model, the Ōtautahi-Oxford Model, that simulates the properties of interstellar objects based on their orbits and likely stellar origins.
The next interstellar object to enter the solar system is likely to be discovered by the Rubin telescope. Objets such as 3I/ATLAS are incredibly faint when they are far from the sun, but Rubin's wide field and large aperture make it ideal for finding interstellar objects. "Rubin's speed means it also scans 18,000 square degrees every few nights," said Bob Blum, Director of Rubin Observatory Operations, in an email. "The combination of depth, field of view, and speed is ideal for finding rare objects."
With all of this in its favor, Rubin is expected to find any interstellar objects sooner than other facilities because it will detect them when they're farther away. "We expect Rubin will be able to find at least multiple 10's of these rare interlopers over the course of its 10-year survey," said Bloom.
It's already begun its work, with Rubin's team locating 3I/ATLAS in test images taken since early June and now studying the object in the night sky.
For astronomers working on how to best detect interstellar objects, the sudden arrival of 3I/ATLAS took them by surprise -- just as they were preparing to begin using the Rubin Observatory. "The solar system science community was already excited about the potential discoveries Rubin will make in the next 10 years, including an unprecedented number of interstellar objects," said co-researcher Dr Rosemary Dorsey of the University of Helsinki. "The discovery of 3I suggests that prospects for Rubin may now be more optimistic; we may find about 50 objects, of which some would be similar in size to 3I."