# More than 5 km across

> Disputed: The nucleus of 3I/ATLAS is more than 5 km across, a radius above 2.5 km.

Source: https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ1P0P0QR0/more-than-5-km-across  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  

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

Answer · 3I/ATLAS

# More than 5 km across

The nucleus of 3I/ATLAS is more than 5 km across, a radius above 2.5 km.

**Disputed** Answers **1** question0

## Where it stands

**Disputed** A measurement falls outside the range it predicts: one piece of evidence for, two against. It needs two reviews to be accepted.

## What it predicts

- No non-gravitational acceleration at the level of the mass loss
- A nucleus at least as bright as a 2.5-km body once the coma fades

## What would rule it out

- A detected acceleration consistent with the mass loss of a kilometre-sized body
- A direct nucleus measurement below 2.5 km

## Evidence 1 for · 2 against

[No acceleration in the early arc](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ48WD5C4Z/no-acceleration-in-the-early-arc)

Speculative

FOR

[The missing acceleration turned up](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ485CADJ6/the-missing-acceleration-turned-up)

Supported

AGAINST

[Two telescopes put the radius below 2.8 km](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ48E606F6/two-telescopes-put-the-radius-below-2-8-km)

Supported

AGAINST

## The questions it answers

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

Open2 answers, none ahead

## Cite it

```
Mysteries Department. (2026). More than 5 km across [Answer ANS0DFQ1P0P0QR0]. https://mysteriesdept.com/r/ANS0DFQ1P0P0QR0
```

Key

**ANS** 0DFQ1P0P0QR0

Kind

Answer · hypothesis

Proposed

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

Version

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