We don’t have long to observe 3I/ATLAS, the interstellar comet that’s currently passing through our Solar System.
It was discovered on 1 July 2025 by the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Rio Hurtado, Chile.
The comet poses no threat to Earth, and is expected to remain a distance of at least 240 million km (150 million miles) away.
However, our Solar System is merely a temporary home for this frozen ball of dust and ice from deep space, as it will eventually exit our cosmic neighbourhood and continue its journey across the Universe.
That’s why astronomers are using our most powerful telescopes and space observatories to learn as much about this interstellar visitor as they can, before it’s gone forever.
3I/ATLAS is one of only three known interstellar objects to have entered our Solar System, the others being 1I/ʻOumuamua, discovered in 2017, and 2I/Borisov, discovered in 2019.
It’s already been observed by the Hubble Space Telescope and the Gemini North Telescope, and now NASA’s SPHEREx and James Webb Space Telescope taken a look, revealing more about its chemical makeup.
SPHEREx view of 3I/ATLAS
NASA’s SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) observed comet 3I/ATLAS between 7–15 August 2025.
Scientists say SPHEREx was able to make ‘multi-spectral observations’ of the interstellar comet, which means the space observatory analysed light coming from 3I/ATLAS to learn more about its chemical composition.
Mission scientists say SPHEREx detected an abundance of carbon dioxide gas in its ‘coma’, which is the name for the gassy atmosphere surrounding a comet.
It also found water ice in the comet’s nucleus.
SPHEREx’s analysis was made when the comet was about 470 million km (290 million miles) from the Sun.
You can find out more via the science brief Research Notice of the American Astronomical Society.
Webb’s view of 3I/ATLAS
The James Webb Space Telescope also observed comet 3I/ATLAS, this time on 6 August 2025, using its Near-Infrared Spectrograph instrument.
Webb’s observations also found the interstellar comet is rich in carbon dioxide and contains water ice, water vapour, carbon monoxide and carbonyl sulfide.
You can find out more in Webb’s 3I/ATLAS data preprint.
What next for 3I/ATLAS?
Comet 3I/ATLAS remains visible from now and into September 2025, but shortly thereafter it will be too close to the Sun to be seen from Earth.
However, it will reemerge from the Sun’s glare and become visible once again in early December 2025, as it continues its journey across our Solar System.
Once it has disappeared from view, it will be gone forever.
But before that happens, scientists are using our most powerful scientific observatories to find out more about what makes this strange object from deep space tick, and what it can teach us about the Universe.