The Hubble Space Telescope has captured the sharpest image yet of interstellar comet 3I/ATLAS, which is currently passing through our Solar System.
Observations by Hubble have enabled astronomers to better estimate the size of the comet's nucleus, which is made of dust and ice.
Hubble managed to capture a dust plume being ejected by the comet, as well as a glimpse of a dust tail streaming away from its nucleus.
An interstellar visitor
3I/ATLAS is one of only three interstellar visitors ever observed passing through our Solar System, the other two being 1I/ʻOumuamua, discovered in 2017, and 2I/Borisov, discovered in 2019.
These objects originate from deep space and make a brief detour through our Solar System, then continue on their journey across the cosmos.
Comet 3I/ATLAS (2025) was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 1 July 2025, when it was 675 million kilometres from the Sun.
Hubble's image, captured on 21 July 2025, follows an earlier Gemini North Telescope image of 3I/ATLAS, which you can see below.
3I/ATLAS is currently visible through telescopes and will be into September 2025, but after this time it will pass too close to the Sun to be seen from Earth.
It's expected to reappear on the other side of the Sun and be visible again in early December 2025.
3I/ATLAS is traveling through our Solar System at 210,000 kilometres per hour, making it the speediest Solar System visitor ever seen.
Astronomers say its speed suggests it's been zooming through interstellar space for billions of years, sped up by the gravitational force of stars and nebulae.
Hubble's view of 3I/ATLAS
Data on 3I/ATLAS gathered by the Hubble Space Telescope suggests it must be as wide as 5.6 kilometres at most, and at least 320 metres.
But astronomers say that, although Hubble has helped refine these estimates, the heart of the comet still cannot be seen at the moment.
It's thought that observations by other observatories like the James Webb Space Telescope will help refine what we know about the comet, including its chemical makeup.
3I/ATLAS's dusty tail
Comets are frozen balls of dust and ice, and so when they get close to a star like our Sun, they heat up, and some of that frozen material turns into gas, streaming away from the comet.
Hubble has captured one such dust plume emerging from the side of the comet that's facing the Sun.
Data suggests 3I/ATLAS is losing dust at a rate consistent with comets that are detected around 480 million kilometres from the Sun.
Yet while the vast majority of comets that we know of originated on the outer edges of our Solar System, this interstellar visitor likely originated in some other Solar System, far beyond our Galaxy.
If you manage to capture an image of 3I/ATLAS, we'd love to see it! Send it to us via contactus@skyatnightmagazine.com
