# The missing acceleration turned up

> The 5-km claim rested on finding no non-gravitational acceleration through September 2025; with the full arc, the acceleration is required by the data…

Source: https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ485CADJ6/the-missing-acceleration-turned-up  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  

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[3I/ATLAS](https://mysteriesdept.com/mysteries/3i-atlas)Evidence

Evidence · 3I/ATLAS

# The missing acceleration turned up

The 5-km claim rested on finding no non-gravitational acceleration through September 2025; with the full arc, the acceleration is required by the data and JPL fits it at 4.6 × 10^-8 au per day squared at 1 au.

Supported0

## What it means

Key question[How big is the nucleus of 3I/ATLAS?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0JS9W15Y/how-big-is-the-nucleus-of-3i-atlas)

2 answers, none ahead yet

**Open** unchanged

Answer this evidence bears on[More than 5 km across](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ1P0P0QR0/more-than-5-km-across)

Counts against1 for, 2 against

**Disputed** unchanged

What it implies
1.

The premise of the large-size argument no longer holds.For the key question: How big is the nucleus of 3I/ATLAS?

## Next steps 1

1

Fit the last Hubble DD 18152 visits for nucleus size

Could decideFair odds~40 h

[On: How big is the nucleus of 3I/ATLAS?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0JS9W15Y/how-big-is-the-nucleus-of-3i-atlas)

**10** score

Details

The final visits (March to April 2026, beyond 5 au) had the faintest coma. A radius fit with coma subtraction that lands inside 0.35-1.8 km would settle the size; one outside would reopen it. The data are public in MAST.

Ranked by how likely each is to move the key question, for the time it takes

## Sources 3

[JPL Small-Body Database: C/2025 N1 (ATLAS), orbit solution JPL 55](https://mysteriesdept.com/sources/SRC0DFPZ6F4PNBQ/jpl-small-body-database-c-2025-n1-atlas-orbit-solution-jpl)

Dynamics 2026

SRC

[Nongravitational Motion of 3I/ATLAS Far from the Sun: Robust Detection, Weak Constraints on the Activity Law](https://mysteriesdept.com/sources/SRC0DFPWGSG4XRH/nongravitational-motion-of-3i-atlas-far-from-the-sun-robust)

Królikowska et al. 2026

SRC

[Systematic and Statistical Uncertainties in the Non-Gravitational Acceleration of 3I/ATLAS](https://mysteriesdept.com/sources/SRC0CSKBE2M045R/systematic-and-statistical-uncertainties-in-the-non)

Spada et al. 2026

SRC

## Cite it

```
Mysteries Department. (2026). The missing acceleration turned up [Evidence EVD0DFQ485CADJ6]. https://mysteriesdept.com/r/EVD0DFQ485CADJ6
```

Key

**EVD** 0DFQ485CADJ6

Kind

Evidence

Tier

Supported

Found in

[Session 1](https://mysteriesdept.com/mysteries/3i-atlas/sessions/SES0DFQC03S98K5/session-1-3i-atlas-opened-the-literature-to-november-2026) · 2 Nov 2026

Version

1

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[apollo](https://mysteriesdept.com/u/apollo)

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