# What pushed 'Oumuamua away from the Sun? · 1I/'Oumuamua > Eight answers have been proposed. None is ahead on the evidence yet. Eight are still possible. Source: https://mysteriesdept.com/mysteries/oumuamua/questions/QST0CSKBZDA67JF/what-pushed-oumuamua-away-from-the-sun 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 pushed 'Oumuamua away from the Sun? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·8 answers·0·0 following **Eight answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Eight answers have been proposed. None is ahead on the evidence yet. Eight are still possible. ## Why it matters The non-gravitational acceleration is the measurement every reading has to reproduce, and it was detected at 30 sigma with no visible gas or dust to account for it⁠[[1]](https://mysteriesdept.com/sources/SRC0CSKB4A401DZ/non-gravitational-acceleration-in-the-trajectory-of-1i-2017)⁠[[2]](https://mysteriesdept.com/sources/SRC0CSKB4HY02PY/spitzer-observations-of-interstellar-object-1i-oumuamua). The answer fixes the composition, and it is the one property that made an artificial reading arguable at all⁠[[3]](https://mysteriesdept.com/sources/SRC0CSKB6R811G8/could-solar-radiation-pressure-explain-oumuamuas-peculiar). An independent re-fit confirms the signal and its radial direction, so the question is the mechanism, not the measurement⁠[[4]](https://mysteriesdept.com/sources/SRC0CSKB4SR7AZY/revisiting-the-trajectory-of-the-interstellar-object). ## Answers 8 [**None of these.** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKC8Y05M28/none-of-these) Not tested enough to call either way Evidence: none yet Still possible [**Outgassing of water or another undetected ordinary volatile from an icy body, below the limits of every…** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKC0W61KZV/outgassing-of-water-or-another-undetected-ordinary-volatile) Not tested enough to call either way Evidence: 3 for, 3 against Still possible [**Release of molecular hydrogen made by cosmic rays inside an ordinary water-ice body, freed as the ice warmed…** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKC5106PB2/release-of-molecular-hydrogen-made-by-cosmic-rays-inside-an) Not tested enough to call either way Evidence: 2 for, 1 against Still possible [**Solar radiation pressure on a natural body with a very low mass-to-area ratio, such as a fractal dust…** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKC6087NHD/solar-radiation-pressure-on-a-natural-body-with-a-very-low) Not tested enough to call either way Evidence: 2 for, 1 against Still possible [**Solar radiation pressure on an artificial lightsail.** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKC6ZG5G17/solar-radiation-pressure-on-an-artificial-lightsail) Failed a test; not refuted outright Evidence: 1 for, 3 against Disputed [**Sublimation of molecular hydrogen ice from a body made largely of it.** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKC2JW01ZS/sublimation-of-molecular-hydrogen-ice-from-a-body-made) Failed a test; not refuted outright Evidence: 1 for, 2 against Disputed [**Sublimation of nitrogen ice from a fragment of an exo-Pluto's surface.** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKC3J40JAH/sublimation-of-nitrogen-ice-from-a-fragment-of-an-exo-plutos) Tested, but the results don't decide it Evidence: 2 for, 3 against Disputed [**The acceleration is an artefact of the astrometry or the orbit fit, not a real force.** ](https://mysteriesdept.com/mysteries/oumuamua/answers/ANS0CSKC86J73W1/the-acceleration-is-an-artefact-of-the-astrometry-or-the) Failed a test; not refuted outright Evidence: 2 against Disputed [Show 3 more answers] ## History 1. 2018[Micheli et al. puts forward: outgassing of water or another undetected ordinary volatile from an icy body, below the limits of every…](https://mysteriesdept.com/sources/SRC0CSKB4A401DZ/non-gravitational-acceleration-in-the-trajectory-of-1i-2017) 1. 2018[Bialy & Loeb puts forward: solar radiation pressure on an artificial lightsail.](https://mysteriesdept.com/sources/SRC0CSKB6R811G8/could-solar-radiation-pressure-explain-oumuamuas-peculiar) 1. 2018[Micheli et al. puts forward: the acceleration is an artefact of the astrometry or the orbit fit, not a real force.](https://mysteriesdept.com/sources/SRC0CSKB4A401DZ/non-gravitational-acceleration-in-the-trajectory-of-1i-2017) 1. 2018[Trilling et al.: spitzer limits CO and CO2 to about ten thousand times below what the outgassing model needed; water was not…](https://mysteriesdept.com/sources/SRC0CSKB4HY02PY/spitzer-observations-of-interstellar-object-1i-oumuamua)Against: Outgassing of water or another undetected ordinary volatile from an icy body, below the limits of every… 1. 2018[Micheli et al.: outgassing was the only mechanism the discovery team found physically viable, if the body had comet-like…](https://mysteriesdept.com/sources/SRC0CSKB4A401DZ/non-gravitational-acceleration-in-the-trajectory-of-1i-2017)For: Outgassing of water or another undetected ordinary volatile from an icy body, below the limits of every… 1. 2018[Enriquez et al.: no narrowband radio emission was found from 72 MHz to 11.6 GHz, to 0.08 W at Green Bank.](https://mysteriesdept.com/sources/SRC0CSKB51J2Z8E/breakthrough-listen-observations-of-1i-oumuamua-with-the-gbt)Against: Solar radiation pressure on an artificial lightsail. 1. 2023[Taylor et al.: the light curve shows no secular change in spin, which is in tension with how outgassing comets spin up.](https://mysteriesdept.com/sources/SRC0CSKB42A0E95/fitting-the-light-curve-of-1i-oumuamua-with-a-nonprincipal)Against: Outgassing of water or another undetected ordinary volatile from an icy body, below the limits of every… 1. 2023[Hoang & Loeb: cooling by the escaping hydrogen would cut the volume of warm ice and the gas budget by a factor of five to…](https://mysteriesdept.com/sources/SRC0CSKB8PR0AA5/implications-of-evaporative-cooling-by-h2-for-1i-oumuamua)Against: Release of molecular hydrogen made by cosmic rays inside an ordinary water-ice body, freed as the ice warmed… 1. 2023[Bergner & Seligman: laboratory work shows hydrogen is produced in irradiated water ice and released over a range of temperatures;…](https://mysteriesdept.com/sources/SRC0CSKB8EY4Z1T/acceleration-of-1i-oumuamua-from-radiolytically-produced-h2)For: Release of molecular hydrogen made by cosmic rays inside an ordinary water-ice body, freed as the ice warmed… 1. 2023[Bergner & Seligman: the model code and data are public, so the cooling objection can be tested directly.](https://mysteriesdept.com/sources/SRC0CSKBJF87HNC/oumuamua-h2-code-and-data-for-bergner-and-seligman-2023)For: Release of molecular hydrogen made by cosmic rays inside an ordinary water-ice body, freed as the ice warmed… 1. 2023[Spada: an independent re-fit confirms the acceleration and finds it radial.](https://mysteriesdept.com/sources/SRC0CSKB4SR7AZY/revisiting-the-trajectory-of-the-interstellar-object)Against: The acceleration is an artefact of the astrometry or the orbit fit, not a real force. 1. 2024[Seligman et al.: small near-Earth asteroids with no visible activity show non-gravitational accelerations too large for the…](https://mysteriesdept.com/sources/SRC0CSKB96C0KDQ/two-distinct-populations-of-dark-comets-delineated-by-orbits)For: Outgassing of water or another undetected ordinary volatile from an icy body, below the limits of every… 1. 26 Oct 2026Asked on this site ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/oumuamua/questions/QST0CSKBZDA67JF/what-pushed-oumuamua-away-from-the-sun%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/QST0CSKBZDA67JF/what-pushed-oumuamua-away-from-the-sun%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/QST0CSKBZDA67JF/what-pushed-oumuamua-away-from-the-sun%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/QST0CSKBZDA67JF/what-pushed-oumuamua-away-from-the-sun%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/QST0CSKBZDA67JF/what-pushed-oumuamua-away-from-the-sun%23add-source) Where it fits 1I/'Oumuamua **What pushed 'Oumuamua away from the Sun?** Key question · you're here [ Ask a question under this one ]