A team of astronomers has taken the sharpest-ever picture of the interstellar comet 3I/ATLAS using NASA’s Hubble Space Telescope. The observations provide more information about the comet’s size and physical properties, and will help refine our knowledge about this unexpected visitor from another solar system.
The upper limit on the diameter of the comet’s solid nucleus is estimated to be around 5.6 kilometers (3.5 miles), but could be as small as 320 meters (1,000 feet) across. Hubble’s images also capture a dust plume ejected from the Sun-warmed side of the comet and a hint of a dust tail streaming away from the nucleus.
The comet is traveling through our solar system at an incredible speed of 130,000 miles per hour, making it one of the fastest-moving objects in our solar system. Scientists believe that the comet has been drifting through interstellar space for many billions of years, gaining momentum from gravitational slingshot effects from stars and nebulae.
“We have powerful sky survey capabilities now that we didn’t have before,” said David Jewitt, science team leader for the Hubble observations. “This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene.”
The comet was discovered by NASA-funded ATLAS in July 2025 and will remain visible to ground-based telescopes through September. Further analysis using other NASA missions, including James Webb Space Telescope and TESS, will provide new insights into this third interstellar interloper.
Hubble’s observations demonstrate the power of space exploration and scientific discovery, continuing to make groundbreaking contributions to our understanding of the universe.
Source: https://science.nasa.gov/missions/hubble/as-nasa-missions-study-interstellar-comet-hubble-makes-size-estimate