A team of astronomers has taken the sharpest-ever picture of an unexpected interstellar comet, 3I/ATLAS, using the NASA/ESA Hubble Space Telescope. The observations are allowing them to more accurately estimate the size of the comet’s solid icy nucleus, with a diameter ranging from 320 to 5.6 kilometers.
The images also captured a dust plume ejected from the Sun-warmed side of the comet and a hint of a dust tail streaming away from the nucleus. Hubble’s data suggests a dust-loss rate consistent with comets that are first detected around 480 million kilometers from the Sun, similar to previously seen Sun-bound comets.
The interstellar visitor is traveling through our Solar System at an incredible 210,000 kilometers per hour, the highest velocity ever recorded for a Solar System visitor. This speed suggests it has been drifting through interstellar space for many billions of years.
Discovered on July 1, 2025, at a distance of 675 million kilometers from the Sun, 3I/ATLAS will remain visible to ground-based telescopes until September and is expected to reappear on the other side of the Sun by early December. The paper was published in The Astrophysical Journal Letters and is available online.
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Source: https://esahubble.org/news/heic2509