The Hubble Space Telescope has produced the sharpest image to date of comet 3I/ATLAS, only the third confirmed interstellar object to visit the solar system. The picture, taken on 21 July when the object was 277 million miles from Earth, reveals a dusty coma and the beginnings of a tail, confirming its cometary nature. Data from Hubble indicate that the icy nucleus is no larger than 3.5 miles (5.6 km) across and could be as small as 1,000 feet. Travelling at roughly 130,000 mph (209,000 kph), 3I/ATLAS is the fastest comet yet recorded. Its hyperbolic trajectory shows it originated beyond the solar system and will not be captured by the Sun’s gravity. Discovered on 1 July by the Asteroid Terrestrial-impact Last Alert System in Hawaii, the comet will pass no closer than 1.8 astronomical units from Earth and reach perihelion on 29 October, slightly inside Mars’s orbit. Astronomers plan to monitor the object with ground- and space-based observatories, including the James Webb Space Telescope, to probe its composition and compare it with native solar-system comets. The findings, led by David Jewitt of the University of California, Los Angeles, have been accepted for publication in The Astrophysical Journal Letters. Researchers say improvements in sky-survey capabilities, such as the new Vera C. Rubin Observatory, should accelerate the discovery of similar interstellar visitors in coming years.