# Polarisation unchanged across perihelion, fitted by porous aggregates

> The negative polarisation branch reached -2.7 per cent at 7 degrees before perihelion and -2.9 per cent at 5.5 degrees after it, essentially unchanged…

Source: https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ475QVY2W/polarisation-unchanged-across-perihelion-fitted-by-porous  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  

---

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

Evidence · 3I/ATLAS

# Polarisation unchanged across perihelion, fitted by porous aggregates

The negative polarisation branch reached -2.7 per cent at 7 degrees before perihelion and -2.9 per cent at 5.5 degrees after it, essentially unchanged, and both optical and near-infrared polarimetry are fitted by porous aggregates of sub-micron monomers.

Supported0

## What it means

Key question[What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0HS0K7SD/what-is-3i-atlas-made-of-and-why-is-its-chemistry-so-unlike)

No answer ahead yet

**Open** unchanged

Part of it[What kind of dust gives 3I/ATLAS its unusually deep negative polarisation?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0STJE1SH/what-kind-of-dust-gives-3i-atlas-its-unusually-deep-negative)

No answer ahead yet

**Open** was No evidence yet

Answer this evidence bears on[Porous aggregates of tiny, weakly absorbing grains](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ19DTND2G/porous-aggregates-of-tiny-weakly-absorbing-grains)

Supports1 for, none against

**Still possible** was No evidence yet

What it implies
1.

The dust's structure stayed the same while the gas changed completely.For: What kind of dust gives 3I/ATLAS its unusually deep negative polarisation?

1.

Fluffy, unprocessed dust fits a body that was never strongly heated.For the key question: What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?

## Sources 3

[Dust Properties of the Interstellar Object 3I/ATLAS Revealed by Optical and Near-Infrared Polarimetry](https://mysteriesdept.com/sources/SRC0DFPWGSFHG4Q/dust-properties-of-the-interstellar-object-3i-atlas-revealed)

Choi et al. 2026

SRC

[Extreme Negative Polarisation of New Interstellar Comet 3I/ATLAS](https://mysteriesdept.com/sources/SRC0DFPWGSF6D0A/extreme-negative-polarisation-of-new-interstellar-comet-3i)

Gray et al. 2025

SRC

[Multi-Wavelength Post-Perihelion Polarimetry of Interstellar Comet 3I/ATLAS](https://mysteriesdept.com/sources/SRC0DFPWGSFXBG8/multi-wavelength-post-perihelion-polarimetry-of-interstellar)

Gray et al. 2026

SRC

## Cite it

```
Mysteries Department. (2026). Polarisation unchanged across perihelion, fitted by porous aggregates [Evidence EVD0DFQ475QVY2W]. https://mysteriesdept.com/r/EVD0DFQ475QVY2W
```

Key

**EVD** 0DFQ475QVY2W

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

Added by

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

The record

Every record is open data. Take this one as JSON, with its links and its history.

[JSON](https://mysteriesdept.com/api/v1/records/EVD0DFQ475QVY2W)