# Where in the Galaxy, and how long ago, did 3I/ATLAS form? · 3I/ATLAS > Two answers have been proposed. None is ahead on the evidence yet. Two are still possible. Source: https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-11-02T15:45:16+00:00 --- **0** # Where in the Galaxy, and how long ago, did 3I/ATLAS form? Asked 2 Nov 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·2 answers·0·0 following **Two answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Two answers have been proposed. None is ahead on the evidence yet. Two are still possible. ## Why it matters Its speed and isotopes have been read as a body from the Galaxy's old thick disc, older than the Sun, or as a thin-disc object a few billion years old. The answer says whether planets were forming around the first metal-poor stars. ## Answers 2 [**A thin-disc body a few billion years old** ](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ335PRDVB/a-thin-disc-body-a-few-billion-years-old) Evidence for it, no test yet Evidence: 2 for Still possible [**An old thick-disc body, older than the Sun** ](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ30WEZNY9/an-old-thick-disc-body-older-than-the-sun) Evidence for it, no test yet Evidence: 2 for Still possible ## Next steps 1 1 Repeat the stellar traceback with Gaia DR4 Could shiftFair odds~24 h **9** score Details When Gaia DR4 is released, rerun the backward integration with its larger catalogue and better velocities. A membership probability that moves decisively to thick or thin disc settles which answer leads; a home star within a few parsecs would be a first. Ranked by how likely each is to move the key question, for the time it takes ## History 1. 2024[Kakharov & Loeb: population model: older than 7.6 billion years](https://mysteriesdept.com/sources/SRC0CSKB60T76S4/galactic-trajectories-of-interstellar-objects-1i-oumuamua-2i)For: An old thick-disc body, older than the Sun 1. 2025[Hopkins et al.: population model: older than 7.6 billion years](https://mysteriesdept.com/sources/SRC0CSKBFSA7080/from-a-different-star-3i-atlas-in-the-context-of-the)For: An old thick-disc body, older than the Sun 1. 2025[Eubanks et al.: population model: older than 7.6 billion years](https://mysteriesdept.com/sources/SRC0DFPWGSF06PW/3i-atlas-c-2025-n1-direct-spacecraft-exploration-of-a)For: An old thick-disc body, older than the Sun 1. 2025[Guo et al.: gaia traceback favours the thin disc and finds no home star](https://mysteriesdept.com/sources/SRC0DFPWGSF2F8W/search-for-past-stellar-encounters-and-the-origin-of-3i)For: A thin-disc body a few billion years old 1. 2025[Pérez-Couto et al.: gaia traceback favours the thin disc and finds no home star](https://mysteriesdept.com/sources/SRC0DFPWGSFBE9F/3i-atlas-in-search-of-the-witnesses-to-its-voyage)For: A thin-disc body a few billion years old 1. 2025[Taylor & Seligman: kinematic age of 3 to 11 billion years](https://mysteriesdept.com/sources/SRC0DFPWGSEZJCR/the-kinematic-age-of-3i-atlas-and-its-implications-for-early)For: A thin-disc body a few billion years old 1. 2026[Cordiner et al.: carbon isotopes date the ices to 10 to 12 billion years ago](https://mysteriesdept.com/sources/SRC0DFPWGSFXVMV/isotopic-evidence-for-a-cold-and-distant-origin-of-the)For: An old thick-disc body, older than the Sun 1. 2026[Sky & Telescope: carbon isotopes date the ices to 10 to 12 billion years ago](https://mysteriesdept.com/sources/SRC0DFPZ6F4HSB0/interstellar-comet-3i-atlas-has-cold-ancient-origins)For: An old thick-disc body, older than the Sun 1. 2026[Barry-Taylor: kinematic age of 3 to 11 billion years](https://mysteriesdept.com/sources/SRC0DFPWGSG12RJ/measuring-the-age-and-initial-composition-of-interstellar)For: A thin-disc body a few billion years old 1. Nov 2026[Session 1: raised the question, proposed two answers and found four results bearing on its answers](https://mysteriesdept.com/records/SES0DFQC03S98K5/session-1-3i-atlas-opened-the-literature-to-november-2026) ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form%23discussion) Help with this question [ **Propose an answer** Something the evidence could support or rule out ] [ **Propose an answer** Something the evidence could support or rule out ](https://mysteriesdept.com/signin?next=/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form%23add-answer) [ **Add evidence** A result for or against an answer ] [ **Add evidence** A result for or against an answer ](https://mysteriesdept.com/signin?next=/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form%23add-evidence) [ **Ask a sub-question** A smaller question that would help settle this one ] [ **Ask a sub-question** A smaller question that would help settle this one ](https://mysteriesdept.com/signin?next=/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form%23add-question) [ **Add a source** A paper, archive record or image ] [ **Add a source** A paper, archive record or image ](https://mysteriesdept.com/signin?next=/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form%23add-source) Where it fits 3I/ATLAS **Where in the Galaxy, and how long ago, did 3I/ATLAS form?** Key question · you're here [ Ask a question under this one ]