# Mass loss and push agree on a kilometre-sized body

> Balancing the measured mass loss against the non-gravitational acceleration gives a diameter of 0.82 to 1.05 km; Loeb's group gets a radius of 0.42 km if…

Source: https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ47T6M9BD/mass-loss-and-push-agree-on-a-kilometre-sized-body  
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

# Mass loss and push agree on a kilometre-sized body

Balancing the measured mass loss against the non-gravitational acceleration gives a diameter of 0.82 to 1.05 km; Loeb's group gets a radius of 0.42 km if CO2 drives it and 0.74 to 1.15 km if water does.

Suggestive0

## 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[About a kilometre across, or a little more](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ1MV3GTQV/about-a-kilometre-across-or-a-little-more)

Supports2 for, none against

**Still possible** unchanged

What it implies
1.

An independent, dynamical route to the same size range.For the key question: How big is the nucleus of 3I/ATLAS?

1.

The size depends on which gas is pushing.For: Which gas carries the push: carbon dioxide, water or carbon monoxide?

## 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 2

[Inferring the mass and size of 3I/ATLAS from its non-gravitational acceleration](https://mysteriesdept.com/sources/SRC0CSKBEJ85VWQ/inferring-the-mass-and-size-of-3i-atlas-from-its-non)

Thoss et al. 2026

SRC

[The size of 3I/ATLAS from non-gravitational acceleration](https://mysteriesdept.com/sources/SRC0CSKBEAE5C2C/the-size-of-3i-atlas-from-non-gravitational-acceleration)

Forbes 2025

SRC

## Cite it

```
Mysteries Department. (2026). Mass loss and push agree on a kilometre-sized body [Evidence EVD0DFQ47T6M9BD]. https://mysteriesdept.com/r/EVD0DFQ47T6M9BD
```

Key

**EVD** 0DFQ47T6M9BD

Kind

Evidence

Tier

Suggestive

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

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