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Quick & curious · Space

A comet from outside our solar system.

3I/ATLAS was discovered in July 2025 – only the third known visitor from another star system. It's just passing through.

A blurry bright patch with a small bright core against a black sky: comet 3I/ATLAS, imaged by the Hubble telescope
Image: Images taken by David Jewitt/NASA/ESA/Space Telescope Science Institute (STScI), processed by Nrco0e. · Public domain · Original

61km/sits speed into the inner solar system

How we know

A telescope of the ATLAS network in Chile discovered it on 1 July 2025. Its path is open: it isn't bound to the Sun and will leave the solar system again. Before it, only two such visitors were known: ʻOumuamua and Borisov. It was never a danger to Earth.

Perhaps older than the Sun

Where exactly it comes from is open. If it originated in the so-called thick disk of the Milky Way, it could be at least 7 billion years old – older than our solar system. It came closest to the Sun on 29 October 2025, between the orbits of Earth and Mars.

Sources

Every statement in this discovery is backed by one of these sources and was checked before publication.

  1. Wikipedia: 3I/ATLAS (accessed 2026-10-06)
  2. NASA Science: Comet 3I/ATLAS (accessed 2026-10-06)

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    Image: NASA/SDO/HMI · CC BY 4.0

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