# What shape was 'Oumuamua, and how did it spin? · 1I/'Oumuamua > Three answers have been proposed. None is ahead on the evidence yet. Three are still possible. Source: https://mysteriesdept.com/mysteries/oumuamua/questions/QST0CSKBZWY4KE5/what-shape-was-oumuamua-and-how-did-it-spin Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-26T11:58:22+00:00 --- **0** # What shape was 'Oumuamua, and how did it spin? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·Part of [What was 'Oumuamua made of?](https://mysteriesdept.com/mysteries/oumuamua/questions/QST0CSKBZN458NQ/what-was-oumuamua-made-of)·3 answers·0·0 following **Three answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Three answers have been proposed. None is ahead on the evidence yet. Three are still possible. ## Why it matters The brightness range of about 2.5 magnitudes is the largest of any small body, and the shape bears directly on the acceleration readings: radiation pressure depends on area, outgassing torques on geometry⁠[[1]](https://mysteriesdept.com/sources/SRC0CSKB1W02ZW4/a-brief-visit-from-a-red-and-extremely-elongated)⁠[[2]](https://mysteriesdept.com/sources/SRC0CSKB3TG7PPV/modelling-the-light-curve-of-oumuamua-evidence-for-torque). The light curve allows two very different shapes⁠[[3]](https://mysteriesdept.com/sources/SRC0CSKB3JP48X6/the-excited-spin-state-of-1i-2017-u1-oumuamua). ## Answers 3 [**A long, thin cigar (axis ratio about 1:8 or more) tumbling near its lowest rotational energy state.** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKCE9W2G6M/a-long-thin-cigar-axis-ratio-about-1-8-or-more-tumbling-near) Not tested enough to call either way Evidence: 2 for, 1 against Still possible [**A thin flattened disc (about 1:6) tumbling near its highest rotational energy state.** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKCF9453KG/a-thin-flattened-disc-about-1-6-tumbling-near-its-highest) Not tested enough to call either way Evidence: 3 for Still possible [**None of these.** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKCG8C4HYC/none-of-these) Not tested enough to call either way Evidence: none yet Still possible ## History 1. 2017[Meech et al. puts forward: a long, thin cigar (axis ratio about 1:8 or more) tumbling near its lowest rotational energy state.](https://mysteriesdept.com/sources/SRC0CSKB1W02ZW4/a-brief-visit-from-a-red-and-extremely-elongated) 1. 2017[Meech et al.: a 2.5-magnitude range implies a body about ten times longer than wide.](https://mysteriesdept.com/sources/SRC0CSKB1W02ZW4/a-brief-visit-from-a-red-and-extremely-elongated)For: A long, thin cigar (axis ratio about 1:8 or more) tumbling near its lowest rotational energy state. 1. 2018[Belton et al. puts forward: a thin flattened disc (about 1:6) tumbling near its highest rotational energy state.](https://mysteriesdept.com/sources/SRC0CSKB3JP48X6/the-excited-spin-state-of-1i-2017-u1-oumuamua) 1. 2018[Fraser et al.: the body tumbles, with an axis ratio of at least 5:1.](https://mysteriesdept.com/sources/SRC0CSKB3325J7E/the-tumbling-rotational-state-of-1i-oumuamua)For: A long, thin cigar (axis ratio about 1:8 or more) tumbling near its lowest rotational energy state. 1. 2018[Belton et al.: the spin data fit either a cigar or a very flat spheroid and cannot separate them.](https://mysteriesdept.com/sources/SRC0CSKB3JP48X6/the-excited-spin-state-of-1i-2017-u1-oumuamua)For: A thin flattened disc (about 1:6) tumbling near its highest rotational energy state. 1. 2019[Mashchenko: a cigar of about 1:8 fits but is less probable than a disc (16 against 91 per cent) from the depth of the…](https://mysteriesdept.com/sources/SRC0CSKB3TG7PPV/modelling-the-light-curve-of-oumuamua-evidence-for-torque)Against: A long, thin cigar (axis ratio about 1:8 or more) tumbling near its lowest rotational energy state. 1. 2019[Mashchenko: physical light-curve modelling favours the disc.](https://mysteriesdept.com/sources/SRC0CSKB3TG7PPV/modelling-the-light-curve-of-oumuamua-evidence-for-torque)For: A thin flattened disc (about 1:6) tumbling near its highest rotational energy state. 1. 2020[Seligman & Laughlin: sublimation of a volatile ice drives the axis ratio to extreme values.](https://mysteriesdept.com/sources/SRC0CSKB77W65G2/evidence-that-1i-2017-u1-oumuamua-was-composed-of-molecular)For: A thin flattened disc (about 1:6) tumbling near its highest rotational energy state. 1. 26 Oct 2026Asked on this site ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/oumuamua/questions/QST0CSKBZWY4KE5/what-shape-was-oumuamua-and-how-did-it-spin%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/oumuamua/questions/QST0CSKBZWY4KE5/what-shape-was-oumuamua-and-how-did-it-spin%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/oumuamua/questions/QST0CSKBZWY4KE5/what-shape-was-oumuamua-and-how-did-it-spin%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/oumuamua/questions/QST0CSKBZWY4KE5/what-shape-was-oumuamua-and-how-did-it-spin%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/oumuamua/questions/QST0CSKBZWY4KE5/what-shape-was-oumuamua-and-how-did-it-spin%23add-source) Where it fits 1I/'Oumuamua [**What was 'Oumuamua made of?** ](https://mysteriesdept.com/mysteries/oumuamua/questions/QST0CSKBZN458NQ/what-was-oumuamua-made-of)Key question · most likely an ordinary comet-like planetesimal of water ice and dust under an insulating organic crust (with or without… **What shape was 'Oumuamua, and how did it spin?** You're here · 3 answers, inconclusive [Where did 'Oumuamua come from?](https://mysteriesdept.com/mysteries/oumuamua/questions/QST0CSKC04R56X5/where-did-oumuamua-come-from)Most likely · ejected from another star's planetary system during planet formation, like most interstellar objects should… [ Ask a question under this one ]