A new image of the interstellar comet 3I/ATLAS shows it's becoming more active and its tail is getting longer as it makes its way through our inner Solar System.
The image was captured by both astronomers and students working together with the Gemini South telescope at Cerro Pachón in Chile.
It shows the growing tail of comet 3I/ATLAS, as well as a glowing coma, and also provides new data revealing more about what it's made of.
What we know so far
Comet 3I/ATLAS was discovered on 1 July 2025 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Rio Hurtado, Chile.
It's an interstellar comet, meaning it formed around a distant star in deep space.
The vast majority of comets we observe in the sky originated from within our Solar System, but 3I/ATLAS is only the third known comet to have originated from beyond our Solar System.
It entered our Solar System from deep space, and will eventually exit our Solar System.
Since its discovery, 3I/ATLAS has been imaged by some of the world's most powerful telescopes, both on the ground and in space, including the Very Large Telescope, the Gemini North Telescope, the Hubble Space Telescope and SPHEREx and the James Webb Space Telescope.
Through observations of the comet, scientists have learned a lot about its chemical makeup, its size and its trajectory.
There's even evidence that 3I/ATLAS could be the oldest comet we've ever seen.
3I/ATLAS is due to make close passes of the Sun, Earth, Mars and Jupiter, and may even be visible to rovers and orbiters at Mars and Jupiter over the coming months.
Gemini South reveals a growing tail
Observations with the Gemini South telescope on 27 August 2025 revealed a prominent tail and glowing coma emanating from 3I/ATLAS.
These observations have also given scientists new measurements of the comet's colours and composition.
The team behind this latest image used the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to capture deep, multi-colour images of the comet.
They show a broad 'coma', which is the name given to the cloud of gas and dust that forms around the comet's nucleus, as ice and dust heats up with the comet getting closer to the Sun.
The image also shows a large tail growing from 3I/ATLAS, much more extended than seen in earlier images of the comet.
This shows 3I/ATLAS has become more active as it travels through the inner Solar System and gets closer to the Sun.
The team also gathered information on the light being emitted by the comet – its spectrum – which can reveal more about its composition and chemistry, and how that changes as it passes through the Solar System.
Perhaps most interestingly, these new observations suggest the dust and ice that make up 3I/ATLAS are similar to those of the comets that formed within our Solar System.
That suggests comets from within our Solar System and those from interstellar space share similar formation processes: vital information for cometary scientists.
About the observations
The Gemini South images of 3I/ATLAS were captured as part of an initiative involving both scientists and members of the public, including students from Hawai‘i and La Serena, Chile.
Students were invited to remotely join the Gemini South control room to connect with astronomers and ask questions about interstellar cometary science.
Attendees joined from Europe, New Zealand, and South America.
The program was led by Karen Meech, astronomer at the University of Hawai‘i Institute for Astronomy.
You can re-watch the full session via the video below.
"The primary objectives of the observations were to look at the colours of the comet, which provide clues to the composition and sizes of the dust particles in the coma, and to take spectra for a direct measure of the chemistry," says Meech.
"We were excited to see the growth of the tail, suggesting a change in the particles from the previous Gemini images, and we got our first glimpse of the chemistry from the spectrum.
"As 3I/ATLAS speeds back into the depths of interstellar space, this image is both a scientific milestone and a source of wonder.
"It reminds us that our Solar System is just one part of a vast and dynamic galaxy — and that even the most fleeting visitors can leave a lasting impact."
The public outreach initiative was organised by NSF NOIRLab in collaboration with Shadow the Scientists, a project created to "connect the public with scientists to engage in authentic scientific experiments, such as astronomy observing experiences on world-class telescopes".
