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3I/ATLAS is the third interstellar object ever discovered in our solar system. Telescope observations suggest it is a roughly 7-mile-wide (11 kilometers) comet zooming at more than 130,000 mph (210,000 km/h). Astronomers discovered it in early July as it emerged from beyond the orbit of Jupiter. An analysis of the comet’s composition and unusually flat, straight trajectory revealed that it did not originate within our cosmic neighborhood, and was likely ejected from a distant star system long before our sun ever formed.
The exotic comet has many peculiar properties, from its chemical composition to its large size. This has fuelled speculation that the comet is an alien spacecraft intentionally guided here. That’s almost certainly not the case, but it doesn’t mean that astronomers aren’t excited about studying it to better understand the conditions around other stars, the early Milky Way, and the frontier of interstellar space.
3I/ATLAS reached its closest point to Earth on Friday (Dec. 19) and is now zooming away forever. Research continues to pour in as telescopes around the solar system observe the strange comet's passage.
Latest about 3I/ATLAS
'Interstellar messenger' 3I/ATLAS could be nearly as old as the universe itself, James Webb telescope observations reveal
The comet formed in a cold and distant part of the early Milky Way up to 12 billion years ago, potentially putting it just under 2 billion years the age of the universe.
Scientists propose new plan to 'catch' comet 3I/ATLAS — but we have to act fast
A new study explores the challenges of catching interstellar comets like comet 3I/ATLAS
Newly visible, city-size 'green comet' will soon be ejected into interstellar space — just like 3I/ATLAS
Comet Wierzchoś, also known as C/2024 E1, is rapidly brightening as it approaches its closest point to Earth next week. But experts predict it will eventually be thrown out of the solar system forever, just like the "alien" comet 3I/ATLAS.
Best space photos of 2025
An alien comet, a Martian volcano, a man’s fall from the sun and a groundbreaking telescope’s first images: Here are the most jaw-dropping space photos of 2025.
Interstellar comet 3I/ATLAS is rapidly moving away from us. Can we 'intercept' it before it leaves us forever?
3I/ATLAS has passed its closest point to Earth, meaning we will soon lose sight of it for good. Some scientists want to send a spacecraft to chase down the alien comet — or the next interstellar object.
Interstellar comet 3I/ATLAS makes closest pass of Earth. Where's it heading next?
Everyone's favorite interstellar comet, 3I/ATLAS, flew past Earth overnight, coming within about 168 million miles (270 million kilometers) of our planet.
Comet 3I/ATLAS reaches its closest point to Earth tonight: How to see it
Comet 3I/ATLAS, the third interstellar object ever detected, reached its closest point to Earth overnight from Thursday to Friday (Dec. 18 to 19), and it remains in a good viewing position tonight. Here's how to see it.
NASA eyes 3I/ATLAS with alien-hunting Clipper spacecraft in new image
NASA's alien-hunting Europa Clipper spacecraft took seven hours of ultraviolet observations of interstellar comet 3I/ATLAS while both objects zoom toward Jupiter.
