On August 7, 2025, NASA shared a new image of Comet 3I/ATLAS and an updated estimate of its size. 3I/ATLAS, the 3rd-known interstellar object, was originally estimated to have a diameter of 20 km (12 miles). But with data from the Vera C. Rubin Observatory, astronomers re-estimated the size to be around 10 km (6 miles). And now the Hubble data puts the size of 3I/ATLAS’s nucleus at a diameter of 5.6 km (3.5 miles). But it could be as small as 320 meters (1,050 feet) across.