# No acceleration in the early arc

> Fitting positions from 15 May to 23 September 2025, Cloete, Loeb and Vereš found no acceleration above about 3 × 10^-10 au per day squared, which with…

Source: https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ48WD5C4Z/no-acceleration-in-the-early-arc  
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

# No acceleration in the early arc

Fitting positions from 15 May to 23 September 2025, Cloete, Loeb and Vereš found no acceleration above about 3 × 10^-10 au per day squared, which with JWST's mass-loss rate implies a diameter above 5 km.

Speculative0

## 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)

Supports1 for, 2 against

**Disputed** unchanged

What it implies
1.

Holds only if the acceleration was truly absent; far from the Sun a small push is expected to be undetectable.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 1

[Upper Limit on the Non-Gravitational Acceleration and Lower Limits on the Nucleus Mass and Diameter of 3I/ATLAS](https://mysteriesdept.com/sources/SRC0CSKBF1W2CZA/upper-limit-on-the-non-gravitational-acceleration-and-lower)

Cloete et al. 2025

SRC

## Cite it

```
Mysteries Department. (2026). No acceleration in the early arc [Evidence EVD0DFQ48WD5C4Z]. https://mysteriesdept.com/r/EVD0DFQ48WD5C4Z
```

Key

**EVD** 0DFQ48WD5C4Z

Kind

Evidence

Tier

Speculative

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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